Specific gravity

Workup of polyuria, acute renal failure, and rapid estimate of urine osmolarity.

pH

Normal 4.5-8.5

Workup of renal tubular acidosis, etiologic organisms for urinary tract infection (if >7 consider urea splitters, proteus, pseudomonas, klebsiella), stone disease and management of conditions where urinary alkalinization is required (rhabdomyolysis, salicylate, NSAID overdose).

Protein

Causes for proteinuria (low grade: 1-2 g/day; nephrotic range: 3.5 g/day)

Glomerular (disruption of barrier): glomerulonephritis, nephritic syndrome.

Tubulointerstitial (reduced resorption of freely filtered protein): acute tubular necrosis, acute interstitial nephritis, Fanconi syndrome.

Overflow (Increased production of freely filtered protein): multiple myeloma, acute myeloid leukemia.

Functional: fever, stress, exercise, orthostatic (only when upright), congestive heart failure.

Leukocyte esterase/nitrites

Suggestive but not diagnostic for bacteriuria.

Glucose

If positive, assess for diabetes mellitus.

Ketones

Potential etiologies include fasting, post exercise states, pregnancy, diabetes mellitus.

Bilirubin

Increased in hemolytic processes and hepatocellular disease.

Decreased with biliary obstruction and broad spectrum antibiotic use.

White blood cell count (WBC)

5 leukocytes per high-power field = significant pyuria.

May indicate infection but other causes include calculous disease, strictures, neoplasm, and glomerulonephropathy.

Red blood cell count (RBC)

5 erythrocytes per high-power field = significant hematuria.

Presence of hematuria on dipstick and microscopic urinalysis requires workup.

Epithelial cells

Presence of squamous epithelial cells in the urinary sediment indicates contamination and warrants a repeat urine collection.

Large numbers of transitional epithelial cells may indicate possible neoplasm.

Casts

RBC casts: glomerular disease or vasculitis.

WBC casts: pyelonephritis.

Tubular casts: acute tubular nephritis.

Hyaline casts: concentrated urine devoid of cells.

Waxy casts: advanced renal failure, indicates stasis.

Granular casts: any tubular injury.

Pigmented casts: hemoglobin, myoglobin, bilirubin.

Crystals

Low pH: calcium oxalate, uric acid, cysteine.

High pH: phosphate, struvite.

Bacteria and yeasts

Presence of organisms likely implies infection and must be confirmed by culture.