Renal Failure Lab Tests

The kidney consists of 3 types of tissue; glomerular, vascular and interstitial. Glomeruli can be damaged by primary glomerulonephritis or secondary to diabetes, hypertension or amyloidosis. Blood vessels may be compromised by systemic vasculitis, atherosclerosis, or thromboemboli. The interstitium can be damaged by sickle cell anemia, chronic analgesic use or other medications including antibiotics, proton pump inhibitors and NSAIDS.

Three common laboratory tests plus blood pressure are helpful in determining the etiology of intrinsic renal disease. 

Urine microscopy must be performed on a fresh (<20 minutes old) urine specimen because red blood cell (RBC) casts are very labile. RBC casts are seen in both glomerular and vascular disease. Fatty casts, oval fat bodies and free fat are seen in glomerular disease. The presence of >25 dysmorphic RBCs is a surrogate for RBC casts and is suggestive of glomerular disease. 

By definition, glomerular disease, such as the nephrotic syndrome, has a 24 hour urine protein excretion that exceeds 3.5 g per day. Although vasculitis is often associated with substantial proteinuria, it usually does not reach the level associated with glomerular disease. 

A rapid increase in serum creatinine level over weeks to months is usually associated with vasculitis of the kidney and diseases such as Goodpasture syndrome, Wegener granulomatosis and lupus vasculitis.  Although untreated glomerulonephritis may have a rapid course, renal failure usually develops more slowly with low levels of GFR reached over a period of 2 to 10 years. Interstitial disease has a more indolent course, reaching low levels of GFP over a 10 to 20 year period. 

Other laboratory tests may also be helpful in determining the etiology of intrinsic renal disease. A significantly elevated serum creatine phosphokinase (CK or CPK) level may suggest that elevated serum creatinine is secondary to rhabdomyolysis. Serum cholesterol and 24 hour urine protein excretion are helpful in detecting the nephrotic syndrome. Other specialized tests include; serum and urine protein electrophoresis, antineutrophil cytoplasmic antibody (ANCA) panel, C3 and C4 complement levels, antinuclear antibody (ANA) rheumatoid factor, anti-glomerular basement membrane antibody and cryoglobulins. Positive results may suggest the need for renal biopsy. 

Reference

Gounden V, Bhatt H, Jialal I. Renal Function Tests. [Updated 2024 Jul 27]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK507821/