Dipstick Renal Pathology Flashcards
Specific
Gravity
•Specific gravity of plasma is 1.008-1.010
–urine SG 1.010 = water conserving
–Urine SG > 1.035 is non-physiologic (?X-ray dyes)
•Use to judge borderline results as 1+ protein (SG = 1.005) represents greater loss than 1+ (SG 1.030)
•In SIADH, USGwon’t increase with H2O deprivation
ph
- Metabolism produces acid, so kidney resorbs HCO3-(RTA type 1) and excretes acid in collecting tubules (RTA type 2)
- Kidney physiologic response to systemic metabolic changes and diet make urine pH difficult to interpret
Glucose
•all glucose filtered is resorbed in the proximal tubule until tubular threshold is exceeded at >180 mg/dL
•1+ dipstick ≈ 250 mg/dLplasma glucose
(normal
Proteins
- only albumin is measured
* normal excretion is
Proteins contd
- does not identify immunoglobulins (multiple myeloma)
- accurate measurement requires quantitative assays
- gold standard is 24 hour urine protein
- routine practice uses spot urine albumin to creatinine ratios
- typical urine excretion of creatinine = 1000 mg/day so that the spot urine albumin:creatinineratio = albumin excretion per day
- terms:
- 3.5 gm/day = nephrotic syndrome
- 40% daily variability and contaminating cells have protein
- test is for albumin and NOT globulins, including light chains
- protein = albumin by dipstick
- may be due to renal and non-renal causes
- physiologic: exercise, fever, standing
- pathologic: glomerular basement membrane damage
- follow-up with complete renal function testing:
- urine sediment morphology (blood, casts)
- Serum albumin (if low, then serious urine loss)
- quantitative measure of urine protein loss
- eGFR(corrects for age, sex and weight)
- imaging
Investigation of proteinuria rule out
Rule out transient proteinuria –fever, exercise
Rule out orthostatic proteinuria
Investigation of proteinuria urine sediment abnormal or normal?
1⁰vs 2⁰glomerular disease
- 300 mg/daymacroalbuminemia
Hematuria
•Ignore if female within 5 days of menstruation
•DDxof hematuria from hemaglobinuriaby centrifuging
–Myoglobin will also test positive
•DDxurology (infection, stones, tumor) from nephrology (“…nephritis”)
•Correlate to urine sediment morphology (? RBC casts, dysmorphic rbc’s)
centrifuge sediment red
hematuria
centrifuge supernatant red
dipstick heme negative
beeturia
phenazopyridine
porphyria
other
centrifuge supernatant red
dipstick heme positive either?
myoglobin or hemoglobin
centrifuge supernatant red
dipstick heme positive
plasma color clear
myglobinuria
centrifuge supernatant red
dipstick heme positive
plasma color red
hemoglobinuria
haptoglobin
binds to hemoglobin?
HEMATURIA
Non-hematologic
RBC Cast, dysmorphic RBC’s, protein >500 mg/24 hr
+
glomerulonephritis
Anti-GBM, ANCA, C’ levels, cryoglobulins, Hep B & C, VDRL, HIV, ASLO
renal biopsy
HEMATURIA
Non-hematologic
RBC Cast, dysmorphic RBC’s, protein >500 mg/24 hr
neg
pyuria wbc cast positive
culture eosinophils
tubulointersitial?
HEMATURIA
Non-hematologic
RBC Cast, dysmorphic RBC’s, protein >500 mg/24 hr
neg
Hb S, cytology, UA of family, 24 hour Ca+2/uric acid
tubulointerstitial
HEMATURIA
Non-hematologic
RBC Cast, dysmorphic RBC’s, protein >500 mg/24 hr
neg
Hb S, cytology, UA of family, 24 hour Ca+2/uric acid
imagin positive
cyst stone mass
HEMATURIA
Non-hematologic
RBC Cast, dysmorphic RBC’s, protein >500 mg/24 hr
neg
Hb S, cytology, UA of family, 24 hour Ca+2/uric acid
cytoscopy
urothelial neoplasm
hematuria upper tract - lower tract
- Stones2. Infection3. Neoplasm (urothelial)
The most reliable indicator of glomerular disease in hematuria without rbc casts is?
proteinuria
- 3.5 gm/24 hr: nephrotic
Mimics of 1⁰ Hematuria
- menstruation
- pigments (eg beets)
- anticoagulation
bilirubin
- Does not filter as bound to albumin - circulating albumin bilirubin (unconjugated)
- Test is for conjugated bilirubin (circulating conjugated bilirubin)
- Urobilinogen is colorless (Urobilinogen)
- dipstick bilirubin is positive when direct (i.e. conjugated) bilirubin is increased (negative in hemolysis)
- may appear before clinical jaundice
- relatively insensitive for detecting liver disease
Ketones
•Energy is from fatty acid metabolism (diabetes, starvation)
Acetone, acetoacetate, hydroxybutyrate
urobilinogen
- water-soluble metabolic product of bilirubin absorbed from gut and filtered
- Increased in hemolytic anemia (↑production) and liver disease ( ↓metabolism)
- not seen with obstructive jaundice (no bilirubin to gut)
nitrites
- Nitrates from diet are metabolized to nitrites by bacteria
- sensitive to 105 organisms/ml
- most gram (-) (E. coli, Klebsiella) and some gram (+) (Staph)
- Specific for bacteruria, but not sensitive