Renal Testing Flashcards
What could abnormally colored urine suggest about possible abnormalities?
Abnormally colored urine could point to the presence of blood, bilirubin, certain drugs, or certain foods.
What could cloudy urine suggest about possible abnormalities?
Cloudy urine could point to the presence of bacteria, leukocytes, erythrocytes, or crystals in the urine.
What should you think of if a urine dipstick is heme-positive but the microscopic examination is negative for RBCs?
Consider hemoglobinuria or myoglobinuria.
How does one confirm myoglobinuria?
Confirm with a urine ammonium sulfate test, which precipitates hemoglobin but not myoglobin.
What findings on microscopic urinalysis strongly suggest the presence of glomerular pathology?
RBC casts or crenated (dysmorphic) RBCs strongly suggest a glomerular etiology.
What disease should come to mind if a patient is found to have eosinophiluria?
Consider drug-induced hypersensitive-mediated interstitial nephritis.
What finding on urinalysis is one of the most reliable indicators of underlying renal pathology?
Proteinuria
What is a normal 24-hour urine protein excretion rate?
4 mg/m²/h
What three lab values are consistent with nephrotic range proteinuria?
A 24-hour urine protein excretion rate of >40 mg/m²/h, or >1.0 g/m²/day, or a random urine protein:creatinine ratio >2.
What three diseases are considered exceptions to the rule in that they have significant renal pathology with normal urine sediment and minimal proteinuria?
Renal dysplasia, medullary cystic disease, and obstructive uropathy.
What is the glomerular filtration rate and how is it estimated?
GFR is a measure of overall renal function and can be estimated from creatinine clearance (using a 24-hour collection).
What is the Schwartz formula for estimating GFR in children?
GFR = 0.413 x (height in cm/plasma creatinine in mg/dL)
What are some clinical situations that can cause an elevated BUN:Cr?
An elevated BUN:Cr (>20:1) can indicate prerenal azotemia, increased protein breakdown from increased protein intake, GI bleed, TPN administration, or catabolic states, including corticosteroid use.
What is the FENa, and how does it guide diagnosis of renal pathology?
Fractional excretion of sodium. It measures the percent of filtered sodium that is excreted in the urine. It is helpful in differentiating acute glomerulonephritis and prerenal azotemia from the other causes of acute kidney injury.
What does a FENa <1 usually signify?
FENa is usually <1 in early acute glomerulonephritis and prerenal azotemia and >1 in other causes of AKI.
