Differentials GU

Question 1

Some malignant adrenal masses may rarely contain intracytoplasmic lipid and lose signal on
out-of-phase images:

Answer 1

Some malignant adrenal masses may rarely contain intracytoplasmic lipid and lose signal on
out-of-phase images:

1. Well-differentiated adrenocortical carcinoma (very rare).
2. Metastatic clear cell renal cell carcinoma (RCC).
3. Metastatic hepatocellular carcinoma (HCC).
4. Liposarcoma (typically a predominantly fatty mass that is rarely confused with adrenal adenoma).

Question 2

Pheochromocytoma/paragangliomas are associated with several syndromes:

Answer 2

1. Multiple endocrine neoplasia (MEN) 2A and 2B: Typically bilateral intra-adrenal pheochromocytomas.
2. von Hippel-Lindau.
3. Neurofibromatosis type 1.
4. Carney’s triad (gastric leiomyosarcoma, pulmonary chondroma, and paragangliomas)
5. Hereditary paraganglioma-pheochromocytoma syndrome: SDHD gene mutation, paragangliomas and
   pheochromocytomas (50% risk of malignant pheochromocytomas).

Question 3

Glomus tumours

Answer 3

Paragangliomas of the head and neck are generally called glomus tumors and may be
associated with the tympanic membrane (glomus tympanicum), the jugular foramen
(glomus jugulare), the carotid body (called a carotid body tumor), or the vagus nerve
(glomus vagale).

Question 4

differential of
echogenic renal mass

Answer 4

Angiomyolipoma (AML). An echogenic renal mass is suggestive of AML (due to internal fat
content), particularly when isoechoic to the sinus fat.
Renal calculus.
Milk of calcium, caused by crystals precipitating out of supersaturated solution.
Sloughed papilla, secondary to papillary necrosis, may appear as an echogenic mass in the
collecting system (often calcified).
Intrarenal gas (e.g., infection, recent nephrostomy tube placement).
Malignant neoplasm (atypical appearance).

Question 5

Unilateral delayed nephrogram:

Answer 5

Acute ureteral obstruction.
Renal artery stenosis.
Renal vein thrombosis/compression.
Acute pyelonephritis.

Question 6

Bilateral persistent nephrogram:

Answer 6

Systemic hypotension.
Acute tubular necrosis.
Contrast nephropathy.
Acute urate nephropathy.
Proteinuria (e.g., myeloma kidney).
Bilateral obstructive uropathy.

Question 7

Unilateral prolonged (hyperdense) nephrogram:

Answer 7

Acute ureteral obstruction.
Renal artery stenosis.
Renal vein thrombosis/compression.

Question 8

Unilateral striated nephrogram:

Answer 8

Acute urinary obstructi on (unilateral).
Acute pyelonephriti s.
Renal infarct.
Renal vein thrombosis or vasculiti s.
Renal contusion (typically focal).
Acute radiati on therapy.

Question 9

Bilateral striated nephrograms:

Answer 9

Acute urinary obstructi on (bilateral).
Acute pyelonephriti s.
Acute tubular necrosis.
Hypotension.
Autosomal recessive polycysti c kidney disease
(ARPKD).

Question 10

unilateral enlarged kidney

Answer 10

unilateral enlarged kidney includes:
Pyelonephriti s.
Acute ureteral obstructi on.
Renal vein thrombosis.
Compensatory hypertrophy.

Question 11

differential of
medullary
nephrocalcinosis

Answer 11

Hyperparathyroidism is the most common cause of medullary nephrocalcinosis.

Sarcoidosis (hypercalcemia).

Type 1 renal tubular acidosis (distal type).

Medullary sponge kidney is caused by ectatic tubules in the medullary pyramids that can
lead to stasis and stone formation.

Papillary necrosis.
In children, treatment with furosemide (Lasix) can lead to medullary nephrocalcinosis.

Question 12

cortical nephrocalcinosis include:

Answer 12

Acute cortical necrosis.

Chronic glomerulonephritis.

Chronic transplant rejection.

Hyperoxaluria.

Alport syndrome (hereditary nephropathy and deafness).

Autosomal recessive
polycystic kidney disease.

Question 13

Papillary Necrosis

Answer 13

The commonly used POSTCARD mnemonic may be
helpful to remember all causes:
Pyelonephriti s.
Obstructi on.
Sickle cell disease.
Tuberculosis.
Cirrhosis.
Analgesics (NSAIDS).
Renal vein thrombosis.
Diabetes mellitus.

Question 14

Hydrpnephrosis

Answer 14

Common causes of hydronephrosis
Obstructive (more common):
Obstructing calculus is the most common cause.
Ureteral or bladder malignancy.
External compression of the ureter by a mass or
retroperitoneal fibrosis.

Non-obstructive:
VUR
(post-procedural or Pregnancy (usually right > left).

Question 15

VHL

Answer 15

Clear cell RCCs
Renal Cysts

Question 16

Birt-Hogg-Dubé

Answer 16

Chromophobe RCCs
Oncocytomas

Question 17

Tuberous sclerosis

Answer 17

Slightly increased
risk of RCC
Bilateral AMLs
Renal cysts

Question 18

Hereditary
papillary RCC

Answer 18

Papillary RCCs

Question 19

HLRCC

Answer 19

Multi ple renal
cancer subtypes,
papillary most
common

Question 20

Sickle cell trait

Answer 20

Medullary RCCs