A. Functional
- Urinalysis
- Dipstick: Hematuria, Erythrocytes (RBC), RBC Casts, Proteinuria
- Bactiuria, Leukocytes (WBC), WBC Casts
- Urine Output: oliguria, anuria, polyuria
- Urine Chemistry: electrolytes, protein (albumin, globulin), creatinine
- Blood
- Renal Function: BUN and Creatinine
- Electrolytes: including Ca, Mg, Phosphate
- Serum albumin (and globulin levels)
- Inflammation: complement levels, ESR, consider ANCA, anti-GBM Abs, ANA, etc.
- Calculation of Creatinine Clearance (CrCl)
- 24 hour urine creatinine collection required
- CrCl = {urine creat (mg/mL) x volume (mL)}/{plasma creat (mg/dL) x time (min)}
- Normal CrCl 125 mL/min/1.73m2 or ~80-100mL/min
- Estimation of Creatinine Clearance
- Men CrCl (mL/min) ~ (140-Age)x(weight in kg)/(72xserum creatinine)
- Women CrCl (mL/min) ~ equation above for men x 0.85
- Nuclear medicine imaging (renal scan) can be used to estimate GFR
- Estimation of Protein Losses [1]
- Obtain spot urine protein and creatinine
- Normal protein:creatinine ratio is 0.4 = Up/Uc
- Estimate 24 hour urine protein in gm = (estimated creatinine clearance x Up/Uc)/5
- Requires that urine protein and urine creatinine be in the same units
- Normal 24 hour Urine Collection Values
- Normal 24 hour urine creatinine 15-25 mg/kg
- Normal 24 hour calcium <200 mg/day
- Normal 24 hour citrate <320 mg/day
- Normal 24 hour cysteine <200 mg/day
- Normal 24 hour oxalate <44 mg/day
- Normal 24 hour uric acid <600 mg/day
B. Non-Invasive Radiography
- Abdomen
- KUB Radiograph (Kidney, Ureter, Bladder); detects ~80% of renal stones
- Poor for evaluation of other problems
- Ultrasound: dilated pelvices, cysts, shadows of stones
- Computerized Tomography (CT)
- Good delineation of renal and other structures, shape
- Angiography with intravenous contrast dye
- Magentic Resonance (MR)
- Good delineation of structure, vascular involvement of tumors
- MR Angiography - does not require contrast dye
- Inflammatory Lesions
- Indium Labelled WBC (infection, inflammation) - usually preferred for abdominal studies
- Gallium Scan (infection, inflammation; high intestinal background)
C. Invasive Testing
- Vascular Angiography: IVP (intravenous pyelogram); very good for stones, obstruction
- Retrograde Pyelogram: Ureters
- VCUG: voiding cystourethrogram. Assess reflux nephropathy
- Bladder Assessment: Cystogram, cystoscopy
- Urethra: Urethrogram
D. Structure / Function Tests
- Nuclear Medicine
- DMSA: Tubular secretion only (nephrogram); not filtered
- DTPA: Exclusively for evaluation of glomerular filtration
- May be used to assess for renal artery stenosis with captopril dosing
- This is called "captopril renogram"
- Magnetic Resonance Angiography
- Easy to assess renal vasculature
- No side effects on function from contrast dye
- Spiral CT angiography is "gold standard" for vessel assessment
E. Proteinuria Evaluation
- Usually detected first by urine dipstick showing >1+ protein
- If urine dipstick shows >1+ protein, then further evaluation should be done
- Urinary microscopic examination
- 24 hour urine collection for total protein
- If 24 hour urine has >150mg of protein, then urine protein electrophoresis should be done
- Urinary protein electrophoresis (UPEP) will detect albumin versus other (smaller) molecules
References
- Ginsberg JM, Chang BS, Matarese RA, Garella S. 1983. NEJM. 309:1543