Kidneys

Question 1

How often are multiple renal arteries reportedly found?
In which kidney is this most common?

Answer 1

• 13% of dog kidneys
• 10% cat kidneys
• Left kidney is more common

Right kidney more commonly has multiple renal veins

Question 2

Where do the capsular arteries commonly arise from?

Answer 2

• Phrenicoabdominal and adrenal arteries

Question 3

What is the role of the vasa recta capillaries?

Answer 3

• Extend from the cortec into the medulla, reabsorbing water from the collecting ducts and returning it back to systemic circulation
• Help to maintain hypertonicity of the renal medulla through countercurrent exchange system

Question 4

What structure helps to maintain renal autoregulation of blood flow?

Answer 4

Macula densa (between glomerulus and afferent arterioles)

Question 5

What cells within the glomerulus are responsible for filtration?

Answer 5

• Podocytes - water and small particles under 60,000 daltons can freely pass through the filtration slits
• Inherent negative charge of the glomerulus basement also enhances the selective nature of filtration

Question 6

What is normal urine production?

Answer 6

20-45ml/kg/d

Question 7

What is the osmolality of the glomerular filtrate and of the medullary interstitial fluid?

Answer 7

• Glomerular filtrate - 300mOs/L
• Medullary interstitial fluid - 1200-1400mOs/L

Question 8

What is normal renal blood flow?

Answer 8

• Approx 25% of CO
• 4ml/min/g of renal tissue

Calculated as renal perfusion/renal vascular resistance

Question 9

How does GFR relate to blood flow?

Answer 9

GFR is roughly 20% of renal plasma flow

Question 10

What determines the concentrating ability of the kidney?

Answer 10

Based on renal medullary hyperosmolarity which is maintained by the vasa recta through a counter-current mechanism

Question 11

What can cause decreased concentrating ability of the kidney?

Answer 11

Increased blood flow through the vasa recta
- Vasodilation
- Increased arterial pressure
- Increased fluid volume

Question 12

What mechanisms create medullary interstitial hyperosmolarity?

Answer 12

• Faculative diffusion of large molecules (urea) into the interstitium
• Limited ability of water to diffuse into interstitium
• Active transport of Na, K, Cl and other electrolytes into the interstitium from the thick portion of the proximal loop of Henle

Urea contributes 40-50%. Absorbed in the collecting ducts UT-A1, stimulated by ADH. It is then recycles by moving to thin limb of Loop of Henle

Question 13

What suture pattern caused increased renal parenchymal damage?

Answer 13

Horizontal mattress
- parenchymal necrosis, fibrosis, scarring and atrophy

Question 14

List some indications for renal surgery

Answer 14

• Unresponsive pyelonephritis
• Perinephric abscess or cyst
• Unilateral renal neoplasia
• Severe renal trauma
• Ureteral consitions causing severe irresolvable hydronephrosis

Question 15

What factors increase the risk of haemorrhage during renal surgery?

Answer 15

• Hypertension
• Thrombocytopaenia
• Azotaemia - inhibits platelet adhesion and aggregation. Should perform BMBT

Question 16

What is the rate of pulmonary metastasis with primary renal neoplasia?

Answer 16

• Dog: 16-48%
• Cat: 43%

Question 17

Which lateral radiographs is better for viewing both kidneys?
What is the normal kidney size?

Answer 17

• Right lateral
• Dogs: 2-2.5x length of adjacent vertebra
• Cats: 2-3x length of adjacent vertebra

Question 18

What imaging modality of best for determining the GFR (and therefore function) of the kidneys?

Answer 18

Nuclear scintigraphy

Plasma clearance tests are more accurate but more difficult to perform and time consuming

Question 19

What radiopharmaceuticals can be used for scintigraphy of the kidney?

Answer 19

• Technitium 99m - DTPA (diethylenetriaminepentaacetic acid)
• Technetium 99m - MAG3 (mercaptoacetyltriglycine) - better for patients with very limited renal function and for performing renal perfusion studies to evaluate transplant patients

Question 20

Where is the most common location of renal ectopia?

Answer 20

Pelvis

Question 21

What breeds are predisposed to polycystic kidney disease?

Answer 21

• Persians (37-38% of breed)
• Bull Terriers

Question 22

What breeds are overrepresented with renal calculi?
What is the most common calculi?
List potential causes of renal calculi

Answer 22

• Siamese cats, Bichon Frise
• Calcium oxalate

Oversaturation of the urine with calculogenic substances
- Organ dysfunction
- neoplasia
- Increased Ca intake
- Drugs
- Increased intestinal absorption
- Impaired renal reabsorption
- Excessive skeletal mobilisation

Question 23

List options for stone removal

Answer 23

• Extracorporeal shockwave lithotripsy
• Nephrotomy
• Pyelolithotomy
• Endoscopic nephrolithotomy (intracorporeal lithotripsy)

Question 24

What are the most common renal neoplasias in cats and dogs?

Answer 24

Cats: Lymphome
Dogs: Carcinoma

Question 25

What inherited neoplastic condition of the kidneys can effect young GSD?

Answer 25

Renal cystadenocarcinoma with nodular dermatofibrosis - Bilateral multifocal renal tumours - Firm nodules of dense collagen in the skin and SQ - Feline common also have uterine leiomyoma - Mutation of FLCN gene, affecting folliculin (a potentially tumour suppressing portein) - 50% mets

Question 26

List paraneoplastic syndromes which can be seen with renal neoplasis

Answer 26

- Polycythaemia and thrombocytosis in cats - HyperCa - Hypoglycaemia - Leucocytosis - Peripheral neuropathy

Question 27

What is the rate of bilateral renal neoplasia?

Answer 27

4-32%

Question 28

What is the MST for renal neoplasia?

Answer 28

- Carcinoma - 16m - Sarcoma - 9m - Nephroblastoma - 6m - HSA - 278d (haemoperitoneum has significantly shorter survival 62d

Question 29

List some DDx of abnormal appearance of the kidney

Answer 29

- Developmental abnormalities - Calculi - Neoplasia - Acquired renal cyst - Perirenal pseudocyst - Renal abscess - Trauma - Kidney worms (Dioctophyma renale)

Question 30

List some treatment options for severe renal trauma?

Answer 30

- Ureteronephrectomy - Wrap in semielastic polyglactin mesh - Wrap in polyglycolic acid mesh - Sterile, nonabsorbable cyanoacrylate for small lacerations *When comparing mesh to partial nephrecomy, creatinine clearance ratio was 0.93 for mesh and 0.58 for partial nephrectomy*

Question 31

List some contraindications for renal biopsy What needle can be used?

Answer 31

Contraindications: - Uncontrolled coagulopathy - Hypertension - Large or multiple renal cysts or abscesses - Extensive pyelonephritis - Ureteral obstruction - Severe hydronephrosis Monopty biopsy needle

Question 32

What is the complication rate of surgical renal biopsy? What factors have been associated with increased complications?

Answer 32

- Complications 1-21.7% (Major in 8.9% - Mortality rate less then 3% Factors associated with complications: - Thrombocytopaenia - Prolonged clotting times - Creatinine above 5mg/dL - Patient older than 4yo - BW less than 5kg

Question 33

List some indications for nephrotomy

Answer 33

- Biopsy - Removal of nephroliths or other obstructive lesions - Chronic infection - Persistent haematuria of renal origin - Persistent hydronephrosis

Question 34

What are the 2 options for nephrotomy?

Answer 34

- Bisectional nephrotomy (sharp dissection of the renal parenchyma) - Intersegmental nephrotomy (Blunt dissection) Bisectional recommended - faster, easier, no difference in post-op GFR between the 2 techniques

Question 35

What should be the maximum occlusion time of the renal vessels?

Answer 35

20min

Question 36

How do you close a partial nephrectomy?

Answer 36

- Overlapping mattress sutures through the parenchyma and apposition of the overlying capsule - If cannot be apposed, can tack omentum to exposed surface

Question 37

List potential complications following a partial nephrectomy

Answer 37

- Haemorrhage - Urine leakage - Urine fistula

Question 38

What is the expected orientation of the renal vessels?

Answer 38

- When in normal orientation, renal vein is ventral to renal artery - When the kidney is rotated ventromedially, renal artery is lateral to renal vein

Question 39

How many ports are required for a laparoscopic nephrectomy?

Answer 39

- 3 to 4 port technique (1 caudal to umbilicus, 1 caudal to last rib and 1 cranial to pelvic limb for triangulation)

Question 40

List some DDx of abnormal appearance of the kidney

Answer 40

- Developmental abnormalities - Calculi - Neoplasia - Acquired renal cyst - Perirenal pseudocyst - Renal abscess - Trauma - Kidney worms (Dioctophyma renale)