Introduction to renal testing Flashcards
what are the essential functions of the nephron?
- maintain constant extracellular environment
- secrete enzymes and hormones
- catabolize peptide hormones
what does BUN measure? what is it related to?
- amount of nitrogen in the blood in the form of urea
- related to the metabolic function of liver and excretory function of kidney
what organ is responsible for excretion of urea?
liver
is azotemia related to an decreased or increased BUN? what are causes of azotemia?
- high BUN
- dehydration
- hypovolemia
- shock
- CHF
- MI
- GI bleed
- protein supplementation
what are causes of a decreased BUN?
- liver failure
- overhydration
- negative nitrogen balance (malnutrition / malabsorption)
- pregnancy
- nephrotic syndrome
can GFR be measured directly? what are the filtration markers?
- cannot be measured directly
- creatinine
- cystatin C
creatinine is a catabolic product of __________
creatinine phosphate
what causes increased creatinine levels?
diseases affecting renal function
what causes decreased creatinine?
decreased muscle mass
what is a normal (postrenal) BUN : creatinine level? prerenal? renal?
- postrenal (normal): 10-20 : 1
- prerenal: over 20 : 1
- renal: under 10 : 1
creatinine clearance is proportional to _________
GFR
what is the normal pH of urine?
- normal: 4.5 - 8.0
- usually: 5.0 - 6.5
does dehydration cause a high or low specific gravity?
high
if you get a false positive for blood in the urine, what is the follow up test?
microscopy
urine microalbumin is ordered for patients with what conditions?
DM, HTN
if you have 3 abnormal urine dipstick tests, what is performed next?
24 hr urine collection
what is the cause of glomerular proteinuria?
increased filtration of macromolecules across glomerular capillary wall (usually albumin)
what is the cause of tubular proteinuria?
malfunctioning tubule cells no longer metabolize or resorb normally filtered proteins (poor function)
what is the cause of overflow proteinuria?
protein overwhelms the ability of the tubules to resorb filtered proteins
most cases of high proteinuria are due to which type?
glomerular
definition: pyuria
over 4 WBC/HPF in a clean voided specimen
definition: hematuria
over 3 RBC/HPF on 2/3 urine samples
- hematurie
- proteinuria
- RBC casts
- dysmorphic RBCs
what is the source of the blood?
glomerular hematuria
- hematuria
- proteinuria
what is the source of the blood?
renal (tubular, interstitial, vascular)
what is the source of the blood in a patient with only hematuria (no proteinuria, etc)?
urologic hematuria - tumors, calculi, infection
what type of epithelial cells in the urine are the only type of importance?
tubular
definition: casts
clumps of material or cells that form in the renal distal and collecting tubules
RBC casts - diagnosis?
glomerulonephritis
WBC casts - ddx?
- pyelonephritis
- glomerulonephritis
- interstitial nephritis
- tubular epithelial acute tubular necrosis
- interstitial nephritis
- eclampsia
- glomerulonephritis
fatty casts - ddx?
- nephrotic syndrome
- hypothyroidism
waxy / broad casts - ddx?
advanced renal failure
cystine crystals are seen in what disease? what is the inheritance pattern?
cystinuria - autosomal recessive
what is the most common type of stone?
calcium oxalate
what type of stone is seen in ehtylene glycol poisoning?
calcium oxalate
calcium oxalate crystals are seen in what conditions?
- ethylene glycol poisoning
- acute renal failure
struvite stone are seen in infection from what organism?
proteus
proteus infection causes what type of stone?
struvite
what is the most common intrinsic cause of acute renal failure in the hospitalized patient?
ATN
what is the standard test for diagnosis of UTI?
quantitative urine culture
what type of casts are seen in nephritic syndrome?
RBC
- high CK
- high Mb
- UA blood
- neg RBCs
diagnosis?
rhabdomyolysis
UA+ for eosinophils - diagnosis?
(allergic) interstitial nephritis
what are the major indications for renal biopsy (4)?
- isolated glomerular hematuria with proteinuria
- nephrotic syndrome
- acute nephritic syndrome
- unexplained acute or rapidly progressive renal failure
