GU 3 -- Diffuse renal parenchymal disease
Terms
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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?
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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?
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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?
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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?
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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?
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Chronic renal vein thrombosis
Postobstructive atrophy
Prior radiation treatment
Renal hypoplasia - What are the additional findings that suggest chronic renal artery stenosis?
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Delayed nephrogram
Delayed pyelogram - What develops late after injection in RAS?
- Hyperdense pyelogram
- Why do these findings occur?
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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?
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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?
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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?
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Remove source of infection
Kidney will not be functional after such severe infection anyway - 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?
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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?
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Pyelonephritis
Acute ureteral obstruction - What are the uncommon causes of striated nephrogram?
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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
- What if the gas is localized to one part of the kidney?
- Can try IV abx and percutaneous drainage of the emphysematous region