Pocket Medicine

NEPHROLOGY

URINALYSIS

PROTEINURIA

• Urine dipstick

1+ 30 mg/dL, 2+ 100 mg/dL, 3+ 300 mg/dL, 4+ >2 g/dL; interpretation depends on SG; eg, 3+ in very concentrated urine might not indicate heavy proteinuria

Insensitive for microalbuminuria and myeloma light chains

•  Spot urine: protein (mg/dL)/creatinine (mg/dL)  g/d of proteinuria (NEJM 1983;309:1543) unlike urine dipstick, will accurately measure myeloma light chains reliable surrogate for 24-hr urine, esp. 1st morning void (JASN 2009;20:436); inaccurate if AKI depends on Cr production, ∴ underestimates if muscular, overestimates if cachectic

•  Microalbuminuria (30–300 mg/24h or mg/L or mg/mg of Cr): early sign of glomerular vascular disease; marker for ↑ risk of CV adverse outcomes (JAMA 2001;286:421)

•  Orthostatic proteinuria: typically in adolescents; ~90% of young  with isolated proteinuria have orthostatic proteinuria; typically resolves spontaneously

HEMATURIA

• Wide, overlapping ages for various etiologies, but general guide for common causes:

<20 y: GN, UTI, congenital; 20–60 y: UTI, nephrolithiasis, cancer

>60 y : prostatitis, cancer, UTI; >60 y : UTI, cancer

Workup (J Urol 2012;188(6 suppl):2473)

•  Urine dipstick if ≥3 RBCs;  dipstick and  sediment → myo- or hemoglobinuria

•  Urine sediment: dysmorphic RBCs or RBC casts → GN → consider renal bx

•  If no evidence of glomerulonephritis:

r/o UTI and non-GU causes (GI or vaginal bleed)

Urine cytology (Se ~70%, Sp ~95%), not adequate substitute for cystoscopy

Renal imaging: helical CT ± contrast (r/o nephrolithiasis and neoplasia of upper tract), cystoscopy (r/o bladder neoplasia, esp. ≥35 y), ± MRI, retrograde pyelogram, U/S