Table 9.1-2. Urinalysis in the evaluation of acute kidney injury

Component

Interpretation

Specific gravity

Estimates urine osmolality

– Values <1.010: Hydrated state

– Values <1.005: Diabetes insipidus or water intoxication

– Values >1.035: Dehydration, high glucose levels, IV contrast

pH

Normal range: 4.5-8.0

– High urine pH: Distal RTA, infections with urea-splitting organisms, vegetarians

– Low urine pH: Metabolic acidosis, dehydration, high-protein diet

RBCs

Positive result may indicate hematuria, hemoglobinuria, or myoglobinuria

WBCs

Suggest inflammation: UTI, GN, or AIN

Ketones

Not normally found in urine. Dipstick tests for presence of acetoacetic acid but not acetone or beta-hydroxybutyric acid. Positive results are associated with uncontrolled diabetes, pregnancy with diabetes, carbohydrate-free diets, and starvation

Glucose

Nearly all glucose filtered by glomeruli is reabsorbed in proximal tubules and undetectable in healthy patients. Positive results are associated with hyperglycemia, pregnancy, and Fanconi syndrome

Bilirubin

Unconjugated bilirubin is not present in urine. Conjugated bilirubin appears in liver disease or obstruction of bile ducts

AIN, acute interstitial nephritis; GN, glomerulonephritis; RBC, red blood cell; RTA, renal tubular acidosis; UTI, urinary tract infection; WBC, white blood cell.