Renal Basics Flashcards by Matt Davis

What are the different Bosniak Classifications for renal cysts?

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What is the CT finding and management of Bosniak 1 cyst

CT finding: Simple cyst (HU 0-20, simple fluid), thin wall, no septa or calcification

~0% risk malignancy
no surveillance unless symptomatic

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What is the CT finding and management of Bosniak 2 cyst

CT finding: Thin septa, fine calcifications, < 3 cm, hyperdense

very low risk malignancy (< 3%)
No surveillance unless symptomatic

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What is the CT finding and management of Bosniak 2F cyst

CT finding: Endophytic, > 3cm, multiple thin septations and calcifications

~5-10% malignant
Periodic surveillance (CT, MRI, or US)

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What is the CT finding and management of Bosniak 3 cyst

CT finding: Thick or irregular septations or walls, increased calcifications, may enhance with contrast

~50% malignant!
surgical excision

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What is the CT finding and management of Bosniak 4 cyst

CT finding: Thick walls, nodularity, marked heterogeneity and calcifications, enhances with contrast

75-90% malignant
surgical excision

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Which Bosniak classifications lack contrast enhancement?

Category 1 to 2F lack contrast enhancement; 3 and 4 enhance

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Difference between ADPKD and ARPKD?

ADPKD: presents in adults

ARPRK: presents in kids

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Polycystic kidney disease presents how?

Innumerable, bilateral renal cortical cysts and hepatic cysts; associated with Berry aneurysms on brain imaging

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CT imaging in a kid shows renal medullary cysts formed at the corticomedullary junction. Dx?

Nephronophthisis

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What is the MCC of genetic ESRD in kids?

Nephronopthisis

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CT scans are the most sensitive study to detect nephrolithiasis, except for which type of stone?

Indinavir calculi (protease inhibitor for HIV)

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Does MRI visualize calculi well?

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Which stones are radiopaque? (Hint: name 4)

Calcium oxalate, magnesium ammonium phosphate (struvite), calcium phosphate, and cystine (poorly opaque)

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Which stone are radiolucent? (Hint: name 5)

Indinavir stones, uric acid, xanthine, ammonium urate, and matrix stones

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Renally derived calcifications that are found in the renal parenchyma are called?

Etiologies?

Nephrocalcinosis

Medullary sponge kidney, hyper-PTH, type 1/Distal RTA, TB, papillary necrosis, hyperoxaluria

Name 3 common developmental renal pseudotumors. What imaging study best distinguishes them?

Dromedary hump
Hypertrophied Column of Bertin
Persistent Fetal Lobulation

DMSA scan (remember, it binds the proximal tubules, highlighting the renal cortex)

DMSA or US scan shows a left renal contour variant with a single bulge on the lateral renal border. Dx?

Dromedary hump

- caused by splenic impression on superolateral border

Imaging shows normal renal variant with enlargement of the cortex between the renal pyramids. Dx?

Hypertrophied Column of Bertin

Imaging shows renal contour indentations in between the renal pyramids. Dx?

Persistent fetal lobulations

due to incomplete renal lobule fusion during fetal development
vs. renal scarring where the indentions are OVER the renal pyramids

At what HU’s should you suspect renal cell carcinoma?

All enhancing masses > 20 HU’s are cancer til proven otherwise

What imaging study can help delineate renal vein/IVC involvement of tumor?

MRI scan with T2-weighted signal intensities

Hyperintense = Clear cell RCC (water filled cells!)
Hypointense = Papillary RCC

In women with enhancing renal mass(es), what additional study should be performed?

Mammogram to r/o breast cancer metastasis

All patients should get what additional imaging if an enhancing renal mass is found?

Chest X-ray (or chest CT if CXR in inconclusive)

Get brain CT if neurologic signs/symptoms present

You should get a bone scan if what laboratory marker is elevated in someone with an enhancing renal mass?

Alkaline phosphatase

Enhanced imaging or angiography showes a renal tumor with a "spoke wheel pattern." Most likely dx?

Oncocytoma - 1/3 of tumors show a "central stellate scar"; however, RCC's can have these central scars as well (one reason why renal biopsy is sometimes indeterminate)

Angiomyolipoma on a CT scan looks how? On an US?

Negative HU's (i.e. fat) within a renal mass - calcifications present, consider it to be carcinoma - beware Epithelioid variant, which has a paucity of fat On US, appears as an echogenic mass which produces a "speed propagation artifact" (sound waves slow in fat, making posterior objects appear further in the distant - pathognomonic: Echogenic mass with no shadowing

This is a benign congenital disorder with multiple cysts in the collecting ducts, nephrocalcinosis, and "paint brush-like calyces"

Medullary sponge kidney | - paint brush-like = bright white calyx (handle) with the pyramid (brush)

CT with contrast shows a focal wedge defect with reduced enhancement, including the rim. Dx?

Pyelonephritis

CT shows decompressed renal pelvis with dilated calyces, parenchymal enhancement, and staghorn calculus. Contrast study or renal nuclear scan shows poor renal function. Dx?

Xanthogranulomatous pyelonephritis - can be confused with RCC - massive caliectasis without pelviectasis is called the "Bears paw sign"

What are some renal buzzwords/findings and their descriptions for GU Tuberculosis? (Hint: name 3)

1. Moth-eaten calyx: calyceal erosion and necrosis (earliest sign) 2. Infundibular stricture and parenchymal calcifications - stricture can cause "phantom calyx" or local caliectasis 3. Putty kidney: caseous necrosis, radiopaque material seen in end-stage renal TB

What ureteral image findings do you see with GU TB?

"Sawtooth ureter": mucosal ulcerations and irregularities/beading - sometimes called corkscrew ureter - strictures most common distally

What GU TB findings do you see in the bladder?

"Thimble bladder:" thickening of bladder wall with reduced capacity

What CT findings are associated with a renal infarct?

Focal wedge defect with reduced enhancement, but the rim of the cortex may enhance due to collateral blood supply (cortical rim sign) - cortical rim sign present ~50% of cases, seen hours to days after infarct

What CT findings are associated with severe renal disease? What size cut-off is generally ominous for end-stage kidneys?

Diffuse increased echogenicity bilaterally, loss of corticomedullary differentiation, and renal atrophy Size of < 9 cm = ESRD, best measured with US