Kidney Flashcards

Question

10) A 30-year-old female has continued ipsilateral loin pain following surgery for pelviureteric junction obstruction. Ultrasound scan shows the renal pelvis to be less dilated than prior to surgery. MAG3 renogram is inconclusive with regard to the question of ongoing obstruction, and a Whitaker test is performed. The maximum pressure difference between the collecting system (antegrade) needle and the urinary catheter is found to be 10 cmH2O. What should the patient be advised regarding the findings of the Whitaker test? a. this invasive test is also inconclusive b. there is no evidence of pelviureteric junction or ureteric obstruction c. there is ongoing pelviureteric junction obstruction d. there is a second previously occult level of obstruction e. the original diagnosis of pelviureteric junction obstruction is in doubt

Answer 1

b. there is no evidence of pelviureteric junction or ureteric obstruction The Whitaker test is a pressure–flow study to evaluate ureteral obstruction or resistance in dilated non-refluxing upper tracts. Being invasive and time-consuming, it is usually performed only when excretory renograms are equivocal. A pressure difference of greater than 15cmH2O is abnormal.

Answer 2

a. xanthogranulomatous pyelonephritis On the IVU, the features of xanthogranulomatous pyelonephritis are unilateral reniform enlargement, ipsilateral renal hypofunction and nephrolithiasis. The condition is probably produced by chronic lowgrade obstruction and chronic bacteriuria. Renal parenchyma is replaced by lipid-laden histiocytes causing renal expansion. This expansion can cause ‘stone fracture’ with obvious separation of the fracture fragments on plain film. Renal tube==rculosis causes dystrophic calcification that can be nodular, curvilinear or amorphous. The calcification is typically multifocal, involving other sites of the urinary tract, and there may be kidney scarring. Hyperparathyroidism causes medullary calcification. Six per cent of renal carcinomas have amorphous, irregular or occasionally curvilinear calcification, while hydatid cysts exhibit curvilinear or heterogeneous calcification

Answer 3

c. sickle cell disease Causes of bilateral smooth renal enlargement include diabetic nephropathy, acute glomerulonephritis, collagen vascular disease, vasculitis, AIDS nephropathy, leukaemia, lymphoma, autosomal recessive polycystic renal disease, acute interstitial nephritis, sickle cell disease, thalassaemia, acromegaly, amyloidosis, myeloma and acute urate nephropathy. When the bilateral renal enlargement is caused by masses, the differential diagnosis includes autosomal dominant polycystic disease, acquired renal cystic disease, lymphoma, metastases, Wilms’ tumours, tuberous sclerosis, von Hippel–Lindau syndrome, multiple oncocytomas and nephroblastomatosis

Answer 4

b. nephroptosis Ptosis of the mobile kidney when erect can cause symptoms and underestimation of parenchymal DMSA uptake. Since the differential function may be a factor in considering removal of a kidney, the technique should account for the possibility of nephroptosis influencing the counts. A nutcracker kidney is a rare cause of left-sided loin pain and haematuria; it is caused by compression of the left renal vein between the aorta and superior mesenteric artery.

Answer 5

d. successful The practice of radiofrequency ablation of renal tumours is emerging. Currently, CT 1 month after the procedure is used to assess treatment success. If enhancing prior to ablation, the tumour is regarded as ablated if there is ,10 HU rise in attenuation following contrast administration. Bulky persistent irregular peripheral enhancement is the commonest appearance of an incompletely treated lesion

Answer 6

a. no further action The abnormality described is prominent or hypertrophic cortex since it takes up DMSA, which in the kidneys is a parenchymal tracer. Renal cell carcinoma, cysts, abscess, haematoma, scar and infarct would be seen as photopenic areas on DMSA SPECT, if large enough.

Answer 7

e. T1W post-gadolinium with pre-contrast T1W signal subtracted The cornerstone of diagnosis here is the post-contrast enhancement of renal cell carcinoma. To identify this among the high T1 signal of haemorrhage or protein within cysts, it is ideal to subtract the precontrast T1 signal. Fat suppression will not remove the distracting high signal from mildly complicated cysts. Risk of renal cell carcinoma is increased in adult polycystic renal disease when in renal failure. Hence caution may be required since at certain levels of renal impairment the use of MRI contrast is not advised

Answer 8

c. sloughed papilla Predisposing factors to papillary necrosis include diabetes mellitus, analgesic nephropathy/abuse, sickle cell disease, pyelonephritis, obstructive uropathy, tuberculosis, trauma, cirrhosis, coagulopathy and renal vein thrombosis. None of the other options easily explains the club-shaped calyx. Blood clots from renal or tumour haemorrhage do cause ureteric colic but tend to elongate along the pelvis and ureter

Answer 9

c. HIV While around 10% of renal and ureteric stones are radiolucent on plain film, almost all are opaque on CT. One exception is the tiny radiolucent calculi formed in patients on protease inhibitors such as indinavir used in the treatment of HIV/AIDS

Answer 10

b. parapelvic cyst The main differential diagnosis for a parapelvic or renal sinus cyst is hydronephrosis. Such cysts may present with pain due to obstructive caliectasis, but rarely cause hydronephrosis. They are found in 1.5% of autopsies and represent 4–6% of all renal cysts. A distinction is made in this question between renal and ureteric colic, the former symptom located to the loin and the latter more typically being loin to groin.

Answer 11

b. haemorrhage from the angiomyolipoma Angiomyolipomas are benign hamartomatous tumours that can occur in the kidneys. They contain fat, smooth muscle and abnormal blood vessels. Eighty per cent are sporadic and occur most often in females aged 50–80 years. Twenty per cent of patients with angiomyolipomas have tuberous sclerosis. Retroperitoneal bleed is the most significant complication and can be catastrophic. The risk increases with size of the lesion due to increased abnormal vasculature. Haemorrhage occurs because of large tortuous vessels and aneurysms. Embolization is performed for symptomatic (flank pain) angiomyolipomas, those that have bled at any size, and prophylactically when over 4cm.

Answer 12

c. left nephrostomy and antibiotics Pyonephrosis secondary to an obstructing calculus is the likely diagnosis. Percutaneous nephrostomy is indicated for temporary or permanent relief of an obstructed urinary system (malignant or benign obstructive uropathy), pyonephrosis, renal stones, iatrogenic ureteric injury, transplant kidney ureteric obstruction, and vesicovaginal fistula. A ‘onestab’ puncture technique or Seldinger technique can be used. For any procedures where urinary infection is suspected or in stone disease, prophylactic antibiotics are mandatory – for example, 80mg gentamicin or 750mg cefuroxime. Clotting must also be checked and if necessary corrected. The major complication rate is around 3% while minor complications occur in around 15%. Major complications are septicaemia, blood loss requiring transfusion, pleural or abdominal viscera puncture, or transcolonic approach. Minor complications include retroperitoneal urine extravasation, clot colic from macroscopic haematuria and tube complications. Tube complications include catheter dislodgement, blockage, leaking, kinking and fracture.

Answer 13

b. calcification Angiomyolipoma should not have calcification whereas it is seen in 10% of renal cell carcinomas. Both these tumours can be hypervascular. The cornerstone of diagnosis of an angiomyolipoma is identifying fat on CT or MRI; however, fat has been reported in renal cell carcinoma, and peripheral or renal sinus fat can become trapped in any large renal tumour

Answer 14

d. renal vein thrombus Differentiation of renal cell from transitional cell carcinoma is helpful for planning surgical treatment since transitional cell carcinoma of the renal collecting system requires the more extensive surgical procedure of nephroureterectomy. Renal vein thrombus is seen with renal cell carcinoma while all other options given are features of transitional cell carcinoma of the kidney. Delayed contrast CToffers a pyelographic phase on which collecting system, ureter and bladder filling defects are clearly demonstrated. A urothelial field effect can occur, resulting in multiple transitional cell carcinomas throughout the renal tract. Renal cell carcinoma, as it expands, tends to distort the renal outline and is more likely to be peripheral and exophytic

Answer 15

b. thorough hydration of the patient A significant contribution to the evidence base used to guide practice in contrast-induced nephropathy (CIN) comes from the NEPHRIC study group. The trial was a randomized, prospective, double-blind, multicentre study performed in 17 centres in Denmark, France, Germany, Spain and Sweden, and consisted of 129 patients. CIN is acute renal impairment with an absolute increase in serum creatinine of at least 0.5mg/dl (44.2 mmol/l) or a relative increase of at least 25% from baseline. A rise of 1mg/dl is less frequently used as the definition. CIN usually peaks on day 2 or 3 following iodinated contrast injection, with a return to baseline within 2 weeks. Return to baseline is not always seen. Low-osmolar iodinated contrast media have a low rate of CIN in the general population – less than 2%. In patients with increased risk of CIN due to diabetes mellitus or pre-existing renal impairment, this rate rises significantly. It has also been shown that low-osmolar contrast causes less CIN than high-osmolar (order of 1800 mosmol/kg water) contrast in high-risk patient groups. No difference in CIN rate is observed in lowrisk groups when iso-osmolar is compared with low-osmolar contrast agents. The NEPHRIC study group shows that in people with diabetes or those with renal impairment having iliofemoral or coronary angiography there is a reduced rate of CIN when using iso-osmolar iodinated contrast as opposed to low-osmolar contrast medium. Osmotic diuresis causing increased sodium load to the distal nephron, with consequent increased medullary work, possible hypoxia and volume depletion giving rise to activation of vasoregulatory hormone systems, is suggested as the reason for the findings. Vigorous hydration is encouraged as perhaps the most important measure to try to avoid CIN. There is evidence both supporting and rejecting the nephroprotective effect of the free radical scavenger acetylcysteine when given before the iodinated contrast media

Answer 16

c. renal mass in keeping with renal cell carcinoma and hepatosplenomegaly without focal hepatic or splenic lesions Stauffer described a syndrome of nephrogenic hepatopathy in which a renal cancer without liver metastases causes hepatosplenomegaly and abnormal liver function. Renal cell carcinoma paraneoplastic phenomena include erythrocytosis and hypercalcaemia.

Answer 17

b. a new site of disease is identified Two criteria are commonly used for assessing cancer response to treatment: WHO and RECIST. The latter stands for Response Evaluation Criteria in Solid Tumours, and it is this tool that is usually used in treatment trials. The WHO criteria compare a summed area product (longest axial dimension multiplied by the longest axial dimension perpendicular to this). RECIST sums the longest axial dimension and compares this across scans. Complete response for both criteria is disappearance of disease, confirmed at 4 weeks. A partial response according to the WHO is 50% or more reduction in the summed area product following treatment and confirmed at 4 weeks. RECIST requires a 30% or greater decrease in the summed longest diameters, confirmed at 4 weeks. Progressive disease is defined as a 25% increase in summed area product for the WHO criteria and a 20% increase in summed longest diameter according to RECIST. Progressive disease also results from the appearance of any new site of disease. Stable disease reflects changes of magnitude that do not achieve partial response or progressive disease

Answer 18

(e) The 'comet tail' sign confirms a ureteric calculus rather than phlebolith lndinavir and pure matrix calculi are the only types of stone not well visualized on CTKUB. The 'soft tissue rim' sign refers to circumferential thickening of the ureteric wall around a calculus as opposed to the 'comet tail' sign which is seen around phleboliths.

Answer 19

(a) Alport syndrome Medullary nephrocalcinosis has a wide differential diagnosis, but options (b), (d) and (e) account for 70% of cases. Other causes include papillary necrosis and drugs such as Frusemide. Alport syndrome (hereditary chronic nephritis) typically gives rise to cortical calcificatio

Answer 20

(b) Oncocytoma In addition to the above findings, a 'spoke-wheel' appearance at angiography and a photopaenic area on 99mrc-DMSA scan may be seen.

Answer 21

(b) Stage Illa Stage I includes tumours that are confined entirely to the kidney. Stage II tumours invade the perinephric fat or adrenal gland on the same side. Stage Illa tumours extend into the renal vein or the IVC. Stage lllb tumours involve local LNs. Stage Illc combines stages Illa and lllb. Stage IV tumours describes those with distant metastases.?

Answer 22

(a) Magnesium ammonium phosphate 70% of staghorn calculi are composed of magnesium ammonium phosphate (struvite stones). The remainder are cysteine or urate stones. These large calculi are often seen in patients with a history of recurrent infections.

Answer 23

(a) The pure blood flow phase lasts for 2 minutes The pure blood flow phase is the first phase of the examination and lasts up to 40 secs (equivalent to an arterial phase study).

Answer 24

(a) Multicystic dysplastic kidney Occult RCC, polyarteritis nodosa, ADPKD and angiomyolipoma are well recognized causes of perinephric haematoma after innocuous trauma. MCDK do not typically bleed externally into the perinephric space.

Answer 25

(c) Amyloidosis Striated nephrograms are transiently seen in acute extra-renal obstruction along with hypotension and intratubular obstruction. Other causes of bilateral striated nephrograms include rhabdomyolysis and cystic renal disease. Causes of a (usually) single striated nephrogram include renal contusion and renal vein thrombosis

Answer 26

(d) Simple cyst Although most cysts are of low attenuation, by far the commonest cause of an otherwise benign appearing, non-enhancing (<10 HU increase), hyperattenuating (normal renal parenchyma approximately 40 HU on unenhanced CT) lesion is a hyperdense cyst containing proteinaceous material. Lipid poor angiomyolipomas are a rare (3-4%) subset of angiomyolipomas.

Answer 27

(c) Urate Although both xanthine and urate stones are radiolucent, urate stones are much more common. Cystine stones are mildly opaque. Calcium oxalate and calcium phosphate stones are radio-opaque

Answer 28

(a) 51 Cr-EDTA GFR is a commonly accepted standard measure of renal function. It can be measured by tracers that are cleared exclusively by glomerular filtration, the most common being 51 Cr-EDTA (the.standard radiopharmaceutical in Europe) and 99mTc-DTPA (more common in the USA).

Answer 29

(c) This lesion should be followed-up The Bosniak classification is a CT classification of cystic renal lesions. Bosniak I are simple cysts, Bosniak II are minimally complicated cysts. Bosniak llf (lesionE1 that should be followed-up) have hairline thin septae and subtle wall enhancement or are intrarenal lesions >3 cm with high density content. Bosniak Ill cysts are complicated lesions with irregular thickened septae, measurable enhancement and coarse irregular calcification. These should be treated surgically. Bosniak IV lesions are clearly malignant with a large necrotic component, irregular wall thickening and solid enhancing elements.

Answer 30

(d) Decreased density of contrast material on IVU An increase in density of contrast material is seen on IVU due to relative increased water reabsorption. Other IVU signs include delayed washout of contrast medium and lack of distension of the collecting system. US findings include peak Renal artery:Aortic velocity >3.5, absence of blood flow during diastole, no detectable Doppler signal in a visualized renal artery, loss of early systolic peak and a resistive index <0.56.

Answer 31

(e) Xanthogranulomatous pyelonephritis XGP is a chronic granulomatous infection in chronic renal obstruction with progressive macrophage infiltration of the renal parenchyma. Fungal renal infections can cause pyelonephritis with fungal balls. Renal sarcoma typically presents with an infiltrative and expansile mass. Mutilocular RCC is a type of a cystic RCC

Answer 32

(d) The patient should stop his metformin for 48 hours after the examination If the serum creatinine is within the normal range, or the estimated GFR is >60 ml/min, then metformin need not be stopped. If these are abnormal then discussion with the clinical team is required.

Answer 33

(b) Analgeslc nephropathy These are the IVU signs of papillary necrosis. There is a wide differential diagnosis for these appearances including diabetes mellitus, SCD, obstructive uropathy, and pyelonephritis. Overall, diabetes is the most common cause, but analgesic nephropathy is particularly common in middle-aged females.

Answer 34

(e) Avid enhancement after contrast medium administration is seen on CT Renal lymphoma typically occurs in B-Cell non-Hodgkin's lymphoma, where it is the second most common organ involved after the haematopoietic and reticulo-endothelial systems. Primary renal lymphoma is uncommon as the normal kidney does not contain significant amounts of lymphoid tissue. Intra-renal lymphoma appears as an ill-defined, homogeneous mass on CT which enhance poorly relative to the surrounding parenel

Answer 35

(c) Renal angiomyolipoma Renal AML is a benign tumour containing fat, smooth muscle and thick-walled blood vessels. They can bleed (50-60% of AMLs > 4cm bleed spontaneously), and can cause haemorrhagic shock (Wunderlich syndrome). Fat on non-contrast CT in the absence of calcification is virtually diagnostic. They can be associated with tuberous sclerosis (in 80% of TS patients), VHL, and NF

Answer 36

(c) Contrast enhanced CT of the abdomen With a high velocity injury and frank haematuria, CT is the investigation of choice. 25% of patients with frank haematuria and blunt trauma have a significant renal injury. Normotensive patients with microscopic haematuria have a significant renal injury in <0.2%.

Answer 37

(e) Renal cell carcinoma RCC is by far the commonest malignant renal tumour. 10% of these tumours calcify

Answer 38

(b) The column of Bertin is isoechoic to renal cortex The column of Bertin is an area of focal cortical hyperplasia, typically seen between the upper and interpolar region. It has the imaging characteristic of renal cortex. Its main clinical significance is that it can be mistaken for a renal tumour. Both renal arteries usually have two divisions. The renal arteries typically arise at the L1/L2 level. The right renal artery is usually longer and lower than the left.

Answer 39

(b) It is cleared mainly by tubular secretion It is mainly cleared by glomerular filtration hence its utility as a GFR agent. It is useful in assessing the degree of obstructive uropathy. 99mTc-MAG3 is cleared by tubular secretion and is the agent of choice in patients with renal insufficiency as it is not GFR dependent.

Answer 40

(d) Medullary cystic disease Medullary cystic disease appears either as a juvenile (rapidly progressive) or as an infantile form. It is characterised by the presence of bilateral small kidneys with numerous small cortico-medullary cysts which give an appearance of increased parenchymal echogenicity, with loss of the corticomedullary junction. Although rare, ADPKD can present in this age group.

Answer 41

(e) Renal artery dissection Renal artery dissection causes the affected kidney to decrease in size due to arterial insufficiency. Ureteric obstruction with hydronephrosis can be a presenting feature of cervical cancer.

Answer 42

(a) Fraley's syndrome Fraley's syndrome is rare, comprising superior infundibular narrowing due to a crossing vessel causing significant loin pain. It is more common in young women and on the right side. If symptomatic surgery is indicated.

Answer 43

(b) Grade II Grade I refers to contusion or non-expanding subcapsular haematoma and is the commonest type. Grade II refers a laceration less than 1cm deep without extravasation. Grade III describes a laceration more than 1 cm deep without extravasation. Grade IV refers to the above or alternatively to a segmental renal artery or vein injury with contained haematoma. Grade V refers to a shattered kidney or to renal pedicle injury

Answer 44

(c) Renal vein thrombosis Renal/iliac vein thrombosis occurs in up to 5% of cases. If it occurs in the immediate post-operative period it is usually due to endothelial injury at the anastomosis site or extrinsic compression. An absence of venous flow can also be observed with Doppler US.

Answer 45

7. d. Angiomyolipoma The finding of fat attenuation values within a renal lesion on CT is diagnostic of angiomyolipoma. This is a benign tumour that is typically hyperechoic on ultrasound and of high signal on T1-weighted MR due to fat. It does not enhance post-gadolinium, in contrast to renal cell carcinoma, which usually does enhance

Answer 46

9. d. Oncocytoma The features described are typical of renal oncocytoma. Oncocytoma is a tubular adenoma that is very rarely malignant. They are often asymptomatic even when large. The central scar is typical and is due to haemorrhage and infarction of the tumour having outgrown its vascular supply. Radiological differentiation from renal cell carcinoma can be very difficult and percutaneous needle biopsy is unreliable. Nephrectomy is therefore often indicated

Answer 47

19. d. MRI MRI is superior to the other imaging modalities listed at ruling out renal vein invasion. CT is still very accurate (reported as high as 96%), but MR has the advantage of being able to accurately differentiate benign from malignant thrombus. MR offers no advantage in detecting nodal disease, however, and patients being considered for curative surgery should undergo staging CT of the chest, abdomen and pelvis. PET does not have a specific role for detecting renal vein invasion

Answer 48

21. e. Uniform wall thickening The Bosniak classification groups cystic renal lesions into one of four categories based on CT/MR appearances. The differentiation between groups II and III is important as group II are typically ‘follow-up lesions’ and group III are ‘surgical lesions’. Features of a Bosniak III lesion include irregular thickened septa, measurable enhancement, coarse irregular calcification, multiloculation, nodularity, uniform wall thickening and margin irregularity

Answer 49

31. d. Xanthogranulomatous pyelonephritis The most likely diagnosis is xanthogranulomatous pyelonephritis. This is a chronic granulomatous infection in a chronically obstructed kidney, often secondary to a staghorn calculus. It often presents insidiously in middle-aged to elderly females. It is most commonly diffuse, but the focal form seen in 15% of cases may provide a diagnostic dilemma as it can be difficult to confidently distinguish from renal cell carcinoma

Answer 50

32. c. Papillary necrosis Papillary necrosis occurs due to ischaemic damage to the medulla of the kidney, and does not primarily involve the cortex. There are many causes including diabetes, analgesic nephropathy, pyelonephritis, renal vein thrombosis and sickle cell disease. It may be localised or diffuse, bilateral or unilateral depending on the cause. Intravenous urogram appearances are varied and include clubbed calyces, calcification and sloughing of necrotic papilla and alteration in the renal contour.

Answer 51

44. e. Medullary sponge kidney The features are those of medullary sponge kidney. This is a non-inheritable condition that produces cystic dilatation of the collecting ducts and nephrocalcinosis; 75% of cases are bilateral and it is usually asymptomatic. It is associated with an increased incidence of infection and urolithiasis but is not thought to predispose to malignancy

Answer 52

45. d. Non-Hodgkin’s lymphoma The most likely diagnosis is non-Hodgkin’s lymphoma. Primary renal involvement is rare, but is often involved either by haematogenous spread or direct invasion. The kidneys represent one of the most common extra-nodal sites of disease in non-Hodgkin’s lymphoma, but are rarely involved in Hodgkin’s disease. Involvement is usually bilateral, with masses of decreased attenuation and mild homogenous enhancement with intravenous contrast on CT. Patency of the renal vessels despite encasement is highly suggestive, as is preservation of the normal renal contour

Answer 53

55. b. Hypertrophied column of Bertin Many lesions may be mistaken for a renal cell carcinoma on imaging, and it is important to be able to differentiate such ‘pseudotumours’ from genuine carcinomas. The features described in the question are consistent with a prominent column of Bertin. This is normal renal tissue located between the pyramids and extending into the renal sinus. The key features include continuity with the cortex, identical echogenicity to normal cortex and the lack of mass effect or renal outline deformity. A dromedary hump is a focal bulge on the lateral border of the left kidney caused by its relationship with the adjacent spleen. Persistent fetal lobulation can be identified by indentations of the renal surface that overlie the space between the pyramids, whereas renal scarring lies directly over the medullary pyramids

Answer 54

56. a. Acute cortical necrosis The features described are typical of cortical nephrocalcinosis. Causes of cortical nephrocalcinosis include acute cortical necrosis, chronic glomerulonephritis, sickle cell disease, Alport syndrome and congenital oxalosis. Acute cortical necrosis is a rare cause of acute renal failure, and is most commonly due to complications of pregnancy such as placental abruption, infected abortion and severe eclampsia

Answer 55

E Renal vein thrombosis Diastolic flow reversal in the renal arcuate arteries on spectral Doppler ultrasound is a feature of renal vein thrombosis. Acute tubular necrosis (ATN) and acute rejection are difficult to distinguish on a single Doppler examination because they both cause an increase in the resistive index (> 0.8). Renal artery stenosis does not cause diastolic flow reversal and classically produces a slow rising parvus et tardus waveform. An arteriovenous fistula is usually the result of renal biopsies and presents as an area of turbulent high flow within the renal parenchyma

Answer 56

D Renal papillary necrosis

Answer 57

A Focal areas of reduced reflectivity in the renal parenchyma

Answer 58

E Xanthogranulomatous pyelonephritis. Xanthogranulomatous pyelonephritis (XGP) is a rare form of low-grade chronic renal infection, characterised by progressive destruction of the renal parenchyma. The histological hallmark is replacement of the renal parenchyma by lipid-laden foamy histiocytes. Women are predominantly affected (in a 3:1 ratio), usually in mid-life (50—60 years) and after a long history of recurrent urinary tract infection or urinary stones. Involvement of both kidneys is exceedingly rare. XGP is diffuse in 90% of cases, but focal XGP can simulate a renal tumour.

Answer 59

C Indinavir phosphate

Answer 60

C On a time activity graph, the time to peak of the right kidney is increased following ACEI.

Answer 61

D Acute renal vein thrombosis

Answer 62

B Renal abscess The presence of gas within a lesion is virtually diagnostic of an abscess but very rarely seen. Immunocompromised patients and those with diabetes are more prone to renal abscess.

Answer 63

B Metastases to the kidney are usually < 3 cm in size and limited to the cortex

Answer 64

C On MRI the necrotic areas tend to be high signal on T2w images with medium signal intensity on Tlw images. It is common to see calcification within the inflammatory mass as well as associated ureteric calcification. The abscess cavities are low attenuation on CT, with surrounding rim enhancement

Answer 65

E Prophylactic haemodialysis in patients with renal impairment does not reduce the risk of CMN. CMN is defined as an increase in serum creatinine by more than 25% or by 44[lmol/L above baseline within 3 days of contrast administration. Prophylactic haemodialysis does not reduce the incidence of CMN but haemofiltration does.

Answer 66

E Preserved renal transplant perfusion ATN is an early complication in cadaveric allografts and frequently resolves spontaneously in 1—3 weeks. The radionuclide imaging findings of ATN are of preserved perfusion but poor renal function and urine excretion. In acute rejection however, there is both impaired renal function and reduced perfusion on radionuclide imaging.

Answer 67

A Ill-defined areas of low attenuation with irregular margins

Answer 68

B Contrast-enhanced CT abdomen and pelvis In the setting of a haemodynamically stable patient with a history of major blunt trauma, CT is the most appropriate imaging investigation

Answer 69

A Extravasation of contrast from the pelvicalyceal system on delayed phase (5 min) images A deep renal laceration that extends into the collecting system is indicative of a grade 4 injury

Answer 70

A It does not opacify during IVU. A parapelvic cyst is located near the renal hilum, does not communicate with the renal pelvis (unlike calyceal diverticula) and therefore does not opacify during IVU. It compresses the pelvis and may cause hydronephrosis.

Answer 71

C High signal on Tlw and T2w sequences Angiomyolipomas appear high signal on both Tlw and T2w sequences due to their high fat content

Answer 72

C Medullary sponge kidney In medullary sponge kidney the kidneys contain numerous medullary cysts which communicate with the tubules and therefore opacify during excretion urography. The cysts contain small calculi giving a ‘bunch of grapes appearance

Answer 73

E Low attenuation (—100 to —50 HU) areas within a large lesion are consistent with an oncocytoma. Large lesions can extend into and engulf the perinephric fat, and can therefore be mistaken for angiomyolipomas (due to fat content).

Answer 74

D Renal cell carcinoma Angiomyolipomas are benign, fat-containing lesions which do not enhance by more than 15 HU and contain low attenuation (—15 to —20HU) fatty areas. Postcontrast enhancement of greater than 20 HU of a solid renal mass is highly suggestive of malignancy.

Answer 75

B Chronic glomerulonephritis

Answer 76

A An elevated resistive index (RI) Mechanical obstruction is associated with elevation of the RI.

Answer 77

B An increasingly dense right nephrogram that remains present after 6 hours

Answer 78

D Renal vein thrombosis The findings are all consistent with renal vein thrombosis, which can be seen in the dehydrated septic neonate. Ultrasound changes of acute tubular necrosis are usually symmetrical.

Answer 79

E Uric acid Uric acid stones are not visible on plain radiographs but are seen on CT.

Answer 80

1. A. Xanthogranulomatous pyelonephritis (XGP). This is most commonly secondary to proteus infection. XGP is discussed elsewhere in this chapter.

Answer 81

11. D. XGP. Whilst the patient presents with the classical renal cell carcinoma (RCC) triad of loin pain, haematuria, and a mass, this triad is actually only present in 30% of patients with RCC. These features are also typically found in XGP. The key finding in this case is of areas of fatty attenuation within the mass, in association with a staghorn calculus. Calculi are found in 80–90% of cases of XGP. The long history of symptoms is also typical of XGP, which can be present for up to 6 months prior to diagnosis. Lymphoma, RCC, and renal oncocytoma would not typically have areas of fatty tissue within them. Angiomyolipomas, in the absence of tuberous sclerosis, are typically solitary. They are usually well defined, unlike in this case, and would rarely reach this size without having previously caused symptoms. XGP is typically found in diabetic patients and is due to proteus infection. Treatment is with nephrectomy.

Answer 82

14. B. Renal oncocytoma. This is a benign renal cell neoplasm responsible for about 5% of all adult primary renal epithelial neoplasms. It typically occurs in elderly men. They usually appear as solitary, well-demarcated, unencapsulated, fairly homogeneous renal cortical tumours. Bilateral, multicentric oncocytomas are seen in hereditary syndromes of renal oncocytosis and Birt–Hogg–Dubé syndrome. A central stellate scar is seen in approximately one-third. However, distinguishing them from RCC on imaging is not reliable. Leiomyoma of the kidney is a benign smooth muscle neoplasm. It appears as a well-circumscribed, homogeneous, exophytic solid mass that shows uniform enhancement on contrast-enhanced CT. It may occasionally be cystic. Metanephric adenoma is a benign renal neoplasm that is more common in middle-aged to elderly females. It is associated with polycythaemia in 10%. It typically appears as a well-defined, unencapsulated, solitary mass that may be hyperattenuating on unenhanced CT. Calcification can be seen in up to 20%. Hemangioma of the kidney occurs as an unencapsulated, solitary lesion that frequently arises from the renal pyramids or the pelvis. Contrast-enhanced CT or MRI may show early intense enhancement, with persistent enhancement on delayed images. Juxtaglomerular cell (JGC) neoplasm or reninoma is an extremely rare, benign renal neoplasm of myoendocrine cell origin, which is associated with a clinical triad of hypertension, hypokalaemia, and high plasma renin activity. It typically appears as a unilateral, well-circumscribed, cortical tumour and often measures less than 3 cm, but otherwise is indistinguishable from other cortical neoplasms.

Answer 83

15. B. Emphysematous pyelitis. The combination of these radiological findings in a septic diabetic patient indicates an infection with a gas-forming organism, usually E. coli. The gas is located entirely within the pelvicalyceal system, as opposed to the renal parenchyma, which would indicate a diagnosis of emphysematous pyelonephritis. The importance is in the urgency of treatment and prognosis. Emphysematous pyelonephritis carries a grave prognosis and often requires nephrectomy for life-saving treatment, whereas the prognosis with emphysematous pyelitis is not as grave and it often responds to antibiotics with possible urinary drainage procedures if necessary

Answer 84

33. B. Cortico-medullary phase. Imaging in the cortico-medullary phase is helpful for showing the normal cortico-medullary pattern in pseudotumours such as prominent columns of Bertin or focal renal hypertrophy. It is also useful for suspected abnormalities such as vascular malformations and pseudoaneurysms of the kidney. The nephrographic phase is best to characterize renal masses. Small parenchymal renal lesions may be hidden in the renal medulla on the cortico-medullary phase and excretory phases. Excretory phases are best to assess for collecting system lesions and the unenhanced scan is best for detection of renal calculi and for using as a baseline in assessing the enhancement characteristics of parenchymal renal lesions.

Answer 85

34. D. Arterial phase CT abdomen. The IVU has surprisingly been helpful in showing a delayed increasing nephrogram, a classical, although uncommon, appearance of renal vein thrombosis. This is also indicated by the history of glomerulonephritis, which can manifest as nephrotic syndrome, the most common cause for renal vein thrombosis. Ultrasound is often successful at identifying a thrombosed right renal vein, but is not useful in assessing the longer left renal vein. Gradient and SE sequences are both helpful in assessing the renal venous system, with GE giving low-signal thrombus and SE giving high-signal thrombus. Arterial phase CT would be too early to show a venous filling defect and thus may not contribute, although it may show a rim nephrogram. Portal venous phase CT is reasonably sensitive at detecting the lack of enhancement within the renal vein and abnormal enhancement pattern within the affected kidney

Answer 86

36. C. Medullary sponge kidney. Hyperparathyroidism, renal tubular acidosis, and medullary sponge kidney are the three most common causes of medullary nephrocalcinosis. The former two conditions are associated with hypercalciuria that results in uniform medullary nephrocalcinosis. Sarcoidosis and multiple myeloma are associated with hypercalcemia resulting in bilateral nephrocalcinosis. Medullary sponge kidney can affect the kidney segmentally, unilaterally, or bilaterally, therefore unilateral nephocalcinosisis is suggestive of medullary sponge kidney. Medullary sponge kidney is characterized by cystic dilatation of collecting tubules. Urine stasis within the dilated tubules predisposes to infection and calculus formation within the dilated tubules or urinary tracts. On excretory urogram, contrast within the dilated tubules produces a striated ‘paintbrush’ appearance of the renal pyramids

Answer 87

49. E. 60 pre-contrast attenuation, 70 post-contrast attenuation. The attenuation of the normal renal parenchyma typically ranges from 30 to 40 HU. That of hyperattenuating renal masses usually is at least 40 HU but no higher than 90 HU on CT without intravenous contrast. Benign cysts are overwhelmingly the most common type of hyperattenuating renal mass and are also known as hyperdense renal cysts. They are usually cysts containing haemorrhage or proteinaceous material. Hyperattenuating cysts should not enhance and therefore cannot be diagnosed with confidence by using unenhanced CT alone. A proper CT examination includes scanning both before and after the administration of intravenous contrast material. Masses that increase in attenuation by 10 HU or less are considered non-enhancing. Masses that increase in attenuation by more than 10 HU are considered enhancing. However, because the standard deviation of attenuation measurements may be more than 10 HU, an attenuation difference of 20 HU or more is a more specific criterion of enhancement

Answer 88

50. C. Perinephric and periureteric stranding. Whilst this observation is sensitive and specific for detecting calculi, it does not have a bearing on stone outcome or urgency of treatment. The site is of value because if the stone impacts, it dictates the therapeutic approach. The size of the calculus can be used to assess the likelihood of spontaneous passage, with calculi over 5 mm more likely to cause obstruction. The density of the calculus has been found to predict the success of extracorporeal shock wave lithotripsy (ESWL). The presence of anatomical variations is also of interest to the urologists in treatment planning, if this becomes necessary.

Answer 89

54. C. Repeat CT in 3–6 months. Solid masses smaller than 1 cm are challenging. Firstly, there is a reasonable chance that a very small solid mass is benign. Secondly, it is often difficult to characterize a mass smaller than 1 cm as solid and enhancing, despite a meticulous technique using state-of-the-art CT and MR imaging. Thirdly, these masses are often too small to biopsy, therefore when encountering a mass that is believed to be solid and is less than 1 cm in size, it is reasonable to observe them with an initial examination with CT or MR at 3–6 months followed by yearly examinations. A full work-up could ensue when the mass reaches 1 cm in size.

Answer 90

53. C. Deep laceration to the collecting system. Renal injuries are classified into five grades of severity by the American Association for the Surgery of Trauma (AAST), with approximately 80% classified as grade 1 (Table 4.1). Most significant injuries manifest as haematuria and no significant urinary tract injury occurs in the absence of gross haematuria and shock. In addition, most significant renal trauma is associated with additional visceral injury.

Answer 91

58. E. Urine leak. Lacerations generally contain clotted blood and therefore do not enhance on scans obtained with intravenous contrast. Contrast enhancement during the pyelographic phase of the CTexamination indicates the presence of a urine leak. A delayed scan of 10–15 minutes may show the extent of the urinary extravasation. Intense enhancement within a laceration during the early phase indicates active haemorrhage. Focal areas of infarction do not enhance (unlike contusions). The cortical rim nephrogram is a sign of a devascularized kidney, which occurs due to laceration of the main renal artery.

Answer 92

59. C. Multiple thin non-enhancing septa. The criteria for a Bosniak IIF cyst are multiple hairline-thin septa with or without perceived (not measurable) enhancement, minimal smooth thickening of wall or septa that may show perceived (not measurable) enhancement, calcification may be thick and nodular but no measurable enhancement present, no enhancing soft-tissue components, and intrarenal non-enhancing high attenuation renal mass (> 3cm). The follow-up is CT or MRI at 6 months, 1 year, and then yearly up to 5 years. The criteria for a Bosniak II cyst that does not require follow-up include few hairline-thin septa with or without perceived (not measurable) enhancement, fine calcification or a short segment of slightly thickened calcification in the wall or septa, homogeneously high-attenuating masses (<3 cm) that are sharply marginated and do not enhance. Thickened irregular or smooth walls or septa, with measurable enhancement, are features ofa Bosniak III cyst and these are surgical lesions unless there are co-morbidities or limited life expectancy, when they may be observed

Answer 93

60. B. HIV-positive patient on antiretroviral therapy. Whilst CT KUB has 95–99% sensitivity for renal calculi, occasionally calculi due to antiretroviral therapy can be undetectable even to CT. Proteus is associated with formation of staghorn calculi and chronic dehydration with calcium oxalate calculi, both of which are radio-opaque. Xanthine calculi and urate calculi are classically not detectable on plain film KUB, but are usually visible on CT KUB.

Answer 94

64. D. Maintenance of reniform shape. Advanced TCC of the collecting system in the kidney can cause distortion of the renal architecture, but typically the reniform shape of the kidney is maintained. As RCC arises in the renal cortex, large tumours of this nature typically distort the normal renal outline. Calcification can rarely occur in both RCCs and TCCs, although perhaps more commonly in RCC. TCC demonstrates calcification in less than 3%, when it is usually diffuse and punctate. Necrosis can occur in both large RCCs and large TCCs, giving a heterogenous enhancement pattern on CT. Renal vein invasion is a more typical manifestation of RCC and both these tumours may be hypovascular compared to normal renal parenchyma on a nephrographic phase of the CT examination.

Answer 95

72. A. Localized cystic renal disease. This is an uncommon, non-familial, and non-progressive disorder of the kidney characterized by the replacement of all or localized areas of a kidney by multiple variably sized cysts. These cysts form clusters that are separated by thin areas of normal renal parenchyma. The aggregated cysts in localized cystic disease can frequently appear like a multi-septate mass, but they do not form a distinct encapsulated mass and do not show mural irregularities, which are characteristics of cystic neoplasms. Multilocular cystic nephroma in adults is much more common in females (female:male 9:1) and manifests as a multi-loculated cystic lesion with hair-like septa and minimal mural enhancement. It is distinguished from localized cystic disease by the presence of a capsule. Typically extension into the central renal sinus is found and multilocular cystic nephroma is often classified on imaging as Bosniak III lesions. Lymphangioma of the kidney is a rare benign cystic tumour that most often arises from the peripelvic region or renal sinus. It may more rarely arise from the lymphatics of the capsule or cortex. In the diffuse form of lymphangiomatosis, the cystic changes occur diffusely in the renal sinus or perinephric region, with a relatively normal appearing renal parenchyma. Clear cell RCC presents as a solid or a cystic lesion, the cystic variant accounting for 4–15% of all RCCs. These lesions typically have nodular or septal enhancement, distinguishing them from benign cystic renal lesions. Multicystic dysplastic kidney is a congenital maldevelopment in which the kidney is completely replaced by cysts with no normal renal parenchyma remaining

Answer 96

73. D. Refer for immediate venous intervention. There are a number of complications to be aware of in the immediate post-transplant period. The most efficient and cost-effective method of surveillance for these is ultrasound. Acute rejection and acute tubular necrosis (ATN) both occur early in the post-transplant phase and can be difficult to differentiate. Both can cause elevation of pulsatility index (PI) (normal <1.5) and resistive index (RI) (normal <0.7), although these tend to be higher with rejection. ATN is more common with cadaveric transplants. It usually resolves within a matter of days or weeks, but ultimately biopsy can be necessary to reliably differentiate these processes. This patient probably had a degree of ATN initially. Arterial occlusion is uncommon and is evident by reduced/absent arterial flow in the main artery as well as in the interlobar arteries, which can demonstrate loss of flow with any cause of severe oedema (e.g. renal vein thrombosis or acute rejection). Renal vein thrombosis causes pain and anuria. It is associated with early treatment with cyclosporine and steroids. It also causes a rise in the RI and PI. The key feature to notice is the persistent flow in the main renal artery, reducing the likelihood of renal arterial thrombosis. There is also a tubular structure noted in the hilum, which is what a thrombosed renal vein looks like, and reversal of diastolic flow on arterial traces

Answer 97

65. C. Chronic non-steroidal anti-inflammatory drug (NSAID) analgesic overuse. The appearances described are those of renal papillary necrosis. This can be due to a number of causes, most commonly analgesic abuse, but also severe renal infection in diabetics, sickle cell disease, haemophilia, and renal vein thrombosis. The causes of chronic renal disease can be subdivided by the effects noted on the renal parenchyma and the papillary/pelvicalyceal system, and whether these are uni- or bilateral. In bilateral cases such as this, no radiological abnormality suggests possible glomerulonephritis, acute tubular necrosis (ATN), acute cortical necrosis, or pyelonephritis. Generalized infiltration of the renal parenchyma suggests amyloid or malignant infiltration (e.g. lymphoma or leukaemia). Papillary/pelvicalyceal abnormalities, in the presence of normal parenchyma, indicate papillary necrosis, medullary sponge kidney, or renal TB. Papillary calyceal abnormality with focal parenchymal loss indicates reflux nephropathy, TB, or calculus. Both parenchymal loss and papillary calyceal abnormalities indicate obstructive nephropathy or severe reflux nephropathy

Answer 98

74. B. PI < 1.5, RI < 0.7, prominence of renal pyramids. PI < 1.5 or RI < 0.7 can be regarded as normal, whilst a PI > 1.8 or RI = 0.9 should be regarded as abnormal. Although both ATN and acute rejection cause the PI and RI to rise, the likelihood of acute rejection is greater with higher values. Complete absence of diastolic flow, or flow reversal, is due to acute rejection in the majority of cases. Morphologically, the transplant kidney is very similar to the native and many of the subtle differences are attributed to the improved resolution of the former. There is a well-defined renal parenchyma peripherally, with a highly reflective echogenic sinus centrally. In distinction to the native kidney, the renal pyramids are more commonly visualized within the transplant, being hypoechoic, relative to the parenchyma itself. Loss of cortico-medullary differentiation is pathological and is a B mode finding that can be associated with acute rejection.

Answer 99

23 Answer D: One-shot IVU following intravenous contrast medium administration In an unstable patient, there is no time for a CT scan, and a `one-shot' IVU would be the simplest and most effective study prior to potential surgery. CT remains the investigation of choice in any blunt abdominal trauma in a stable patient

Answer 100

49 Answer C. Bilateral ureteric obstruction and hydronephrosis from the bladder primary Collecting system opacification is delayed because of the raised backpressure reducing ultrafiltration of contrast at the glomerulus. Delayed imaging will be required to demonstrate the level of obstruction. Urgent urological opinion should be sought as ureteric stenting or nephrostomies may be required to relieve the obstruction

Answer 101

51 Answer A: Unenhanced scan, followed by post-intravenous contrast scans acquired at 60 and 100 seconds An unenhanced scan detects the presence of calcification, which may otherwise be obscured by contrast. The 60-second acquisition shows the corticomedullary phase, where there is differential enhancement of the cortex and the 100-second acquisition shows the nephrogram phase where the renal parenchyma uniformly enhances

Answer 102

52 Answer D: Unenhanced CT abdomen and pelvis, performed prone with low mA dose protocol Virtually all ureteric calculi, even those radiolucent on plain radiography, are detected by CT. A low mA dose protocol is performed without intravenous or oral contrast. The patient lies prone to distinguish between calculi at the vesicoureteric junction and those that have already passed into the bladder; the latter will lie dependently within the bladder.

Answer 103

54 Answer D: Presence of internal calcification AML >4cm are symptomatic in >80%, and bleed spontaneously in 50-60%. Intratumoural calcifications are virtually never present with AML. Rarely renal cell carcinoma can undergo osseous metaplasia with growth of fatty marrow and associated calcifications.

Answer 104

59 Answer A: Renal lymphoma Renal lymphoma is a common site for extra-nodal non-Hodgkin's lymphoma. It usually shows poorer enhancement than renal cortex in the nephrographic phase.

Answer 105

60 Answer C: Lung Recurrence of renal cell carcinoma usually occurs within the first six years after surgery. The risk increases with the initial stage. Distant metastases develop in 20-30% of patients, with lungs the commonest site (50-60%), followed by mediastinum, bone and liver.

Answer 106

61 Answer E: Protease inhibitor use in HIV Indinavir (a protease inhibitor) use results in crystalline stones that are nonopaque on CT. They are demonstrated by contrast-enhanced CT as filling defects in the ureter. * Hyperparathyroidism - calcium oxalate/phosphate calculi, HU>1000 * Chronic urinary infection - struvite (magnesium ammonium phosphate) calculi, HU300-900 * Gout - uric acid calculi, HU 150-500 (radiolucent on plain film) * Cystinuria - cysteine calculi, HU variable 200-880

Answer 107

62 Answer B: Acute cortical necrosis Cortical nephrocalcinosis, described as tramline calcification, can be seen in any cause of acute cortical necrosis, including renal vein thrombosis, although obstetric shock is the commonest cause. Renal damage is more severe than in acute tubular necrosis.

Answer 108

63 Answer D: Multiple simple cysts Multiple simple cysts increase in frequency with age and are the most likely cause in a patient over 50 years with no family history of cysts or cysts in other organs

Answer 109

64 Answer E: Von Hippel-Lindau disease Von Hippel-Lindau disease is an autosomal-dominant disorder, manifestations of which include renal and pancreatic cysts, renal cell carcinoma, and cerebellar haemangioblastomas.

Answer 110

65 Answer B: Autosomal-dominant polycystic kidney disease Autosomal-dominant polycystic kidney disease typically presents clinically with hypertension and renal failure aged 30-50 years, and cysts are present in the liver and pancreas, which along with a family history differentiates this from other causes.

Answer 111

66 Answer A: Acquired renal cystic disease Acquired renal cystic disease occurs in 90% of patients who have been on dialysis for 5-10 years. Innumerable small cysts form and the kidney enlarges over time. Wall calcification is common and they regress following transplantation. Complications include haemorrhage and renal cell carcinoma

Answer 112

68 Answer A: Renal tubular acidosis All are causes of medullary nephrocalcinosis, but distal renal tubular acidosis is the commonest cause in a child. It may be associated with rickets

Answer 113

69 Answer B: Peripheral renal enhancement A stretching injury to the renal artery damages the intima and thrombus can then occlude the artery, which causes non-perfusion of the affected kidney. Capsular vessels do not arise from the main renal artery and so result in peripheral renal enhancement (the rim sign). The kidney may appear otherwise intact. Renal revascularisation should be accomplished within two hours of injury, but can be successful later depending on the collateral supply and extent of injury.

Answer 114

70 Answer D: Abdominal and pelvic CT with intravenous contrast Contrast-enhanced CT is the imaging modality of choice in a stable patient with or without haematuria and with evidence of major flank impact. Both US and IVU have a low sensitivity for detection of renal trauma, which often will not result in free intra-abdominal fluid. No imaging is required for an adult patient with microscopic haematuria, who is haemodynamically stable and with no other indication for CT. Instead observation until haematuria settles is appropriate. However, this does not hold true for the paediatric trauma patient, in whom microscopic haematuria without hypotension can be associated with significant renal imaging and CT imaging is warranted

Answer 115

51 Answer A: Rise in serum creatinine from 80pmol/L to 124pmol/L The definition of contrast-induced nephropathy is an impairment of renal function (an increase in serum creatinine by more than 25 % or 44 pmol/L (0.5 mg/ dL)) which occurs within three days following intravascular administration of contrast medium, in the absence of an alternative aetiology

Answer 116

52 Answer C. Inferior vena caval invasion The role of MRI in staging renal carcinoma is one of problem solving. Invasion of the renal vein and inferior vena cava is better shown on T1 W sequences with and without contrast, particularly in the coronal and sagittal planes.

Answer 117

53 Answer C: Lytic bone metastases 'SFDG is not useful in primary renal or urothelial tumour assessment as it is physiologically excreted in the urine.'8FDG PET-CT is useful for the detection of and response to therapy of lytic bone metastases.

Answer 118

58 Answer D: Cortical depressions between calyces Foetal lobulation occurs due to incomplete fusion of the foetal lobules, leading to a lobulated contour with depressions/interlobular septa occurring between calyces.

Answer 119

59 Answer C: Normal finding The normal renal cortex is hypoechoic or isoechoic to the liver parenchyma. Arcuate arteries may be seen as small hyperechoic foci without shadowing at the corticomedullary junction. The medullary pyramids are hypoechoic to the renal cortex.

Answer 120

60 Answer C: Tc-99m-dimercaptosuccinic acid (DMSA) Tc-99m-DMSA has minimal urinary excretion (<5%) and high cortical binding (50% of dose at four hours post injection), which makes it the ideal agent for assessment of renal cortical activity

Answer 121

63 Answer D: Focal reflux nephropathy (chronic atrophic pyelonephritis) Focal reflux nephropathy is the only condition listed that gives a calyceal abnormality with associated cortical loss. It usually results as a consequence of infection associated with reflux in childhood. It may be widespread or focal in which case it is more common in the upper poles and on the right. The kidney is always small and there may be contralateral compensatory hypertrophy.

Answer 122

64 Answer B: Glomerulonephritis Goodpasture's syndrome is the association of glomerulonephritis and pulmonary haemorrhage secondary to anti-glomerular basement membrane antibodies. The only renal imaging features are symmetrical change in size, initially enlarged, later small, with excessive renal sinus fat.

Answer 123

65 Answer C: Tuberculosis The clinical and radiological features suggest tuberculosis. Cloudy high attenuation dilated calyces represents calcification within caseous pyonephrosis. Calcification is seen in 30% of cases and may result in putty kidney or calcified autonephrectomy. One feature that suggests TB rather than papillary necrosis or focal reflux nephropathy is the relatively poor excretion of contrast in relation to the degree of obstruction.

Answer 124

66 Answer E: A renal pelvic calculus Xanthogranulomatous pyelonephritis is an uncommon chronic inflammation usually associated with proteus infection and 70% have renal pelvic calculi, in which renal calyces and parenchyma are replaced by lipid-laden macrophages, debris and other inflammatory cells. The nephrogram is totally or focally absent in 80%. The generalised form is commoner but a focal form can mimic a renal tumour

Answer 125

68 Answer B: End-to-side anastomosis to the external iliac artery The transplant kidney is usually placed in the contralateral iliac fossa extraperitoneal space. Usually, a live donor kidney is anastomosed end-to-side with the external iliac artery, or less commonly endto-end with the internal iliac artery. An aortic patch is usually removed with a cadaveric transplant; this is not possible with a living donor

Answer 126

69 Answer E: Percutaneous renal biopsy Biopsy is inevitably required to make the diagnosis of rejection. Acute tubular necrosis does have a characteristic pattern on dynamic renal scintigraphy, with almost normal first pass perfusion, blood pool uptake only at 80-180 seconds and no excretion. Rejection may be identified by reduced perfusion with or without swelling. Duplex US and MR findings are non-specific indicators of transplant dysfunction.

Answer 127

70 Answer C: (Peak systolic velocity - End diastolic velocity)/Peak systolic velocity The RI is sensitive to changes in downstream flow resistance and is used to assess changes in diastolic flow in low-resistance vascular beds. The normal limit for a renal transplant is 0.8. The pulsatility index (PI) is calculated by (Peak systolic velocity - End diastolic velocity)/Temporal mean velocity.

Answer 128

22 Answer C: Contrast-enhanced CT Multidetector CT imaging is the gold standard for diagnosing and assessing the extent of renal injury, peri-renal haemorrhage, extravasation of urine, pedicle injury, and associated solid-organ injury. Indications include blunt trauma with (macroscopic or microscopic) haematuria and hypotension, polytrauma, rapid deceleration and penetrating injury

Answer 129

45 Answer A: T2-weighted static fluid MR urography MR urography is indicated as there is no risk of ionising radiation exposure to the foetus. Static fluid sequences are appropriate. Gadolinium contrast is contraindicated in pregnancy

Answer 130

46 Answer C: Alternating bands of hypo- and hyperattenuation of the renal parenchyma This appearance is analogous to the striated nephrogram seen on excretory urography and reflects the underlying pathology of tubular obstruction, interstitial oedema and vasospasm. On delayed (3-6 hours) imaging, the hypoattenuating regions show delayed and persistent enhancement due to prolonged accumulation and transit of contrast through the collecting system. In haematogenous seeding of pyelonephritis (from staphylococcal or streptococcal infections), round peripheral hypoattenuating lesions are seen. They can mimic neoplasia if pyelonephritis is not suspected clinically.

Answer 131

48 Answer D: Ureteral ischaemia Ninety per cent of post-transplant ureteral obstruction is due to ischaemia, usually at the distal ureter close to the ureterovesical junction. This is the area furthest from the renal artery. The other options are also less common causes of obstruction

Answer 132

54 Answer C: Gadodiamide is contraindicated in patients with a glomerular filtration rate (GFR) of <30mL/min There is a causal link between gadolinium-based media and NSF, but no direct proof. There are >200 cases reported, all in patients with renal failure. No cases have been reported in patients with normal renal function. The incidence in at risk patients given Gadodiamide is 3-7 %. Gd-based agents are not recommended as replacements for iodinated contrast. The UK regulatory position as of February 2009 is summarised: 1 Gadodiamide and Gadopentetic acid (Magnevist®) are currently contraindicated in patients with GFR <30 mL/min, including those on dialysis. Gadodiamide is also contraindicated in all patients with renal impairment awaiting liver transplantation. Both agents should be used with caution in patients with GFR 30-59mL/min, & in children <1 year old. 2 Careful consideration should be given before using other Gd-based media in patients with GFR <30mL/min 3 All patients should be screened by history/laboratory tests before administration of Gd-based media 4 Haemodialysis after administration of Gd-based media may remove contrast but there is no evidence that this affects the development or treatment of NSF.

Answer 133

55 Answer B: HIV-related nephropathy The US findings suggest HIV-related nephropathy, a form of glomerulosclerosis, which is the commonest cause of renal impairment in the HIV-positive population. It particularly affects young black males and is the third leading cause of end stage renal disease in African-Americans aged 20- 64 years. Malignancy, HAART therapy and P jirovecii associated nephrocalcinosis are all recognized renal manifestations of HIV infection.

Answer 134

56 Answer E: A wedge-shaped non-enhancing parenchymal area The renal arteries are clamped during the surgery. Damage to the intima may cause local thrombosis and wedge-shaped non-enhancing renal parenchymal infarcts. To promote haemostasis, fat or haemostatic material may be placed in the surgical bed. Fat may later be confused with an angiomyolipoma, and gas bubbles can be present with the latter which may be confused with a gas containing abscess in the early post-operative period. Residual haematoma may have an attenuation of 50-60HU.

Answer 135

57 Answer D: It has a much better prognosis than conventional RCC Papillary RCC is the second commonest form (10-15%) of RCC after clear cell RCC (70%). Both arise from the proximal convoluted tubule. It is more homogeneous and relatively hypovascular; this is a key imaging finding, and is more frequently multifocal and bilateral. It has the best prognosis of all forms of RCC.

Answer 136

62 Answer C: Split renal function Split renal function is assessed with Tc-99m-DMSA or Tc-99m-MAG3 scintigraphy. Dual-phase MDCT with 3-D post-processing is a quick and accurate method for living donor laparoscopic nephrectomy assessment. Of critical importance in the planning and performance of the operation is the renal arterial and venous anatomy

Answer 137

64 Answer D: Periprocedural intravenous hydration Randomised controlled studies and/or meta-analyses have demonstrated reduction in incidence of CIN with periprocedural hydration, low- versus high osmolar and iso- versus low osmolar contrast media. The role of N-acetylcysteine is currently inconclusive

Answer 138

66 Answer C: Autosomal dominant The patient has adult polycystic kidney disease which is autosomally dominantly inherited. Patients are also at risk of mitral valve prolapse and have an increased frequency of renal calculi, urinary tract infections and renal cell carcinoma. Bleeds into cysts are common and painful.

Answer 139

68 Answer A: Conservative management This is a typical description for a subcapsular haematoma which can usually be managed conservatively

Answer 140

69 Answer E: Enlarged kidney with loss of cortico-medullary differentiation The patient has a renal vein thrombosis and the kidney is enlarged due to oedema. There are often hyperechoic areas representing haemorrhage.

Answer 141

4. (a) Renal tuberculosis This appearance is typical of a ‘putty kidney’. This results in a non-functional, shrunken kidney and autonephrectomy. Tuberculosis can involve any part of the genitourinary tract. Renal tuberculosis is usually seen secondary to haematogenous spread from lungs. Renal tuberculosis can manifest in a number of ways including as a renal mass.

Answer 142

7. (b) Renal cortical necrosis This is rare cause of acute renal failure with typical imaging features as given. CT is the most sensitive and specifc imaging for this condition. Absent opacifcation of the cortex with enhancement of juxtamedullary kidney and poor contrast excretion is diagnostic for this condition

Answer 143

18. (b) Autosomal dominant polycystic kidney disease Intravenous urogram appearances are typical due to large cysts distorting the collecting system. Autosomal recessive polycystic kidney disease (infantile type) produces microscopic cysts and on intravenous urography, and shows an initial faint nephrogram with increasingly dense nephrogram.

Answer 144

20. (a) Acute tubular necrosis This is secondary to temporary marked reduction in tubular blood flow. Contrast injection especially in diabetics with glomerulosclerosis is one of the known causes. Typically, the kidneys are enlarged due to interstitial oedema with an immediate dense and persistent nephrogram with absence of contrast from the collecting system

Answer 145

25. (b) Angiomyolipomas The lesions contain fat (negative Hounsfeld units) and show vascularity within. With the history of fts, tuberous sclerosis should be considered as a diagnosis

Answer 146

28. (c) Xanthogranulomatous pyelonephritis This is a chronic suppurative infection characterised by replacement of renal parenchyma by lipid-laden macrophages. In most cases there is also a staghorn calculus with renal enlargement and a rim of cortical enhancement (‘bear paw’ sign).

Answer 147

30. (a) Xanthogranulomatous pyelonephritis Other options are all associated with bleeding or spontaneous haemorrhage.

Answer 148

Answers: (a) Not correct (b) Correct (c) Not correct (d) Not correct (e) Correct Explanation: Medullary sponge kidney is a common sporadic condition affecting young to middle aged adults. There is dysplastic cystic dilatation of papillary and medullary collecting ducts. Meckel- Gruber syndrome is an autosomal recessive syndrome comprising of multicystic dysplastic kidneys, occipital encephalocele and polydactyly. Medullary nephrocalcinosis is visible radiographically in 40% - 80%.

Answer 149

Answers: (a) Not correct (b) Correct (c) Correct (d) Correct (e) Not correct Explanation: Cortex is not involved in renal papillary necrosis. It involves pyramids and medullary papilla. Medullary sponge kidney causes renal papillary calculi not necrosis.

Answer 150

Answers: (a) Correct (b) Correct (c) Correct (d) Not correct (e) Correct Explanation: 5% of RCC are hypovascular on angiography. Tumours cause neovascularity. Renal vein or IVC extension of tumour is also seen on angiograph

Answer 151

Answers: (a) Not correct (b) Not correct (c) Not correct (d) Correct (e) Not correct Explanation: Accessory renal arteries commonly enter the lower pole below the hilum and are more common in patients with horseshoe kidney. Incidence of horseshoe kidney is 1 in 700 births. Duplication of collecting system is seen in only 4% of people.

Answer 152

Answers: (a) Not correct (b) Not correct (c) Correct (d) Not correct (e) Not correct Explanation: Partial voluming tends to overestimate the size of stone on CT.Unenhanced CT shows ureteric and collecting system dilatation, nephromegaly and perinephric and periureteric fat standing, which are all signs of obstruction. lain X-ray KUB has only 45% - 58% sensitivity. Renal failure is rare and is secondary to bilateral obstructing calculi.

Answer 153

Answers: (a) Correct (b) Correct (c) Not correct (d) Correct (e) Not correct Explanation: Hemodialysis can induce hypovolaemia which worsens renal ischemia. Acetylcystein is an antioxidant and scavenger of oxygen free radicals. It enhances the biological effect of the endogenous vasodilator nitric oxide.

Answer 154

Answers: (a) Correct (b) Not correct (c) Not correct (d) Correct (e) Not correct Explanation: AML with minimal fat content can have high attenuation on unenhanced CT. Fat content is characteristic of AML but 5% have predominance of blood vessels or immature fat. Calcification is a rare feature of AML.

Answer 155

Answers: (a) Correct (b) Not correct (c) Correct (d) Correct (e) Not correct Explanation: In renal TB earliest IVU abnormality is a ‘moth eaten’ calyx due to erosion, followed by papillary necrosis. Dilatation of one or more calyces without pelvic dilatation typically occurs due to infundibular stenosis. Tubo-ovarian involvement is usually caused by hematogenous or lymphatic spread, mimicking ovarian cancer clinically and radiologically. Diagnosis is generally made post-operatively.

Answer 156

Answers: (a) Correct (b) Correct (c) Not correct (d) Correct (e) Not correct Explanation: Hepatic cysts are seen in 70%-75% by 60 yrs of age. The most common cause of increased density of cyst is haemorrhage (HU of 50-90). ADKPD patients on dialysis have an increased risk of cancer relative to population.

Answer 157

Answers: (a) Correct (b) Not correct (c) Correct (d) Correct (e) Not correct Explanation: Medullary nephrocalcinosis is seen in hyperparathyroidism, hypervitaminosis D, renal tubular acidosis, medullary sponge kidney, renal papillary necrosis, hypercalciuria and primary hyperoxaluria

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