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54 Cards in this Set

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What is the first question that must be asked when a small kidney is encountered?
Is/are the kidney(s) SCARRED
What is the differential diagnosis of small scarred kidney?
1) Ischemic disease related to small vessel occlusion


2) Reflux nephropathy


3) Analgesic nephropathy
What is always true of renal changes related to analgesic nephropathy and small vessel occlusive disease?
Bilateral involvement .
What is the second question to ask when evaluating small scarred kidney?
Is involvement unilateral or bilateral
What is the DDx for unilateral small scarred kidney?
Reflux nephropathy


Previous renal surgery
What if involvement is bilateral?
Then another question must be asked.
What is the next question to ask if there is bilateral small scarred kidney?
Are the calyces normal or abnormal
What if the calyces are normal?
Then the most likely diagnosis is vascular occlusive disease
What if the calyces are abnormal?
Consider the possibility of bilateral reflux
What if bilateral reflux is not the cause?
Most likely diagnosis is analgesic nephropathy.
What additional findings suggest vascular disease?
Scarring occurs between calyces (in region of interlobar arteries)
What additonal findings suggest analgesic nephropathy?
Scars centered over calyces
What other findings suggest analgesic nephropathy?
Medullary calcification


Evidence of papillary necrosis
What other findings suggest reflux nephropathy?
Cortical thinning over abnormal calyces
What area of kidneys is first affected in reflux nephropathy?
The POLES


Midportion of kidney is initially spared
What if the small kidney is not scarred?
It will be smooth
What is the first question that must be asked when a small, smooth kidney is encountered?
Is there unilateral or bilateral involvement.
What is the most common cause of unilateral small smooth kidney?
Chronic renal artery stenosis
What are other causes of small smooth contoured kidney?
Chronic renal vein thrombosis


Postobstructive atrophy


Prior radiation treatment


Renal hypoplasia
What are the additional findings that suggest chronic renal artery stenosis?
Delayed nephrogram


Delayed pyelogram
What develops late after injection in RAS?
Hyperdense pyelogram
Why do these findings occur?
There is decreased bloodflow to kidney. As contrast in contained in blood, this explains the delayed nephrogram.

The delayed pyelogram occurs because there is decreased pressure head propelling filtrate into the collecting system.


The hyperdense pyelogram also occurs for this same reason. There is decreased volume flow of this IV contrast containing filtrate. The contrast cannot be reabsorbed into the collecting ducts, but the water can, which leaves hyperconcentrated IV contrast.
What are the best tests to evaluate RAS?
radionuclide renogram augmented with captopril


Doppler sonogram


MRA
What is still the gold standard?
Contrast angiogram
What defines a hypoplastic kidney?
Small smooth kidney with 5 OR FEWER CALYCES
What occurs in chronic subcapsular hematoma?
Pressure is exerted on the renal parenchyma, which causes functional ischemia, eventually resulting in renal atrophy.
What is the name for this condition?
Page kidney
What is the history in these cases?
History of flank trauma
Why does renal atrophy result when there has been radiation treatment?
There is parenchymal ischemia due to small vessel arteritis
How common is this?
Rare with today's modern XRT
How long must high grade ureteral obstruction be present (assuming sterile urine) in order to cause irreversible renal damage?
3 weeks
When does the atrophy ensue?
after obstruction is releived
How is the diagnosis made?
1) History


2) Small smooth kidney, with residual calyceal ectasia
What is a nephrographic pattern that must be recognized and acted on immediately?
Shock nephrogram
What is the appearance?
Initial appearance of nephrogram and pyelogram, with subsequent regression of pyelogram and persistence of nephrogram.
Why?
Contrast is administered, and travels to kidneys normally.

Then, during infusion, patient develops severe hypotensive reaction, and perfusion pressure to kidney diminishes. Thus the excreted contrast continues to the bladder, but the contrast that was in the kidney when hypotension ensued will remain.
Why is this being included in this section?
Because the kidneys will also shrink somewhat owing to decreased perfusion, thus bilateral small smooth kidneys.
What is the most common cause of bilateral small smooth kidneys?
Medical renal disease
When there is renal enlargement, what is the first question that must be asked?
Is involvement unilateral or bilateral?
How many categories of abnormalities are there for this pattern?
5
What are they?
Ureteral obstruction


Duplication anomalies


Glomerular hypertrophy


Parenchymal infiltration


Acute vascular abnormalities
What is the most common cause of unilateral smooth renal enlargement?
Hydronephrosis secondary to ureteral obstruction
What parenchymal changes are seen in ureteral obstruction?
Delayed pyelogram phase, which is dilated.
What parenchymal abnormality is sometimes seen in ureteral obstruction?
Striated nephrogram
What is definition of striated nephrogram?
Linear lucencies extending from renal medulla to the renal cortex
What are the common causes of striated nephrogram?
Pyelonephritis


Acute ureteral obstruction
What are the uncommon causes of striated nephrogram?
Autosomal recessive polycystic kidney disease


Acute renal vein thrombosis


Renal contusion
What is a rare cause of striated nephrogram?
Acute radiation nephritis
Why do duplication abnormalities result in renal enlargement?
There is just increased renal tissue mass
What are causes of renal parenchymal infiltration?
Inflammatory processes (pyelo, XGP)
What type of pyelonephritis is treated specially?
Emphysematous
How is it treated?
NEPHRECTOMY
Why?
Remove source of infection


Kidney will not be functional after such severe infection anyway
What if the gas is localized to one part of the kidney?
Can try IV abx and percutaneous drainage of the emphysematous region