urinalyses

Urinalysis, commonly referred to in the plural as urinalyses, is a laboratory test of urine used to screen, diagnose, and monitor a range of conditions affecting the kidneys, urinary tract, or other body systems. A typical urinalysis comprises three parts: physical examination, chemical analysis, and microscopic examination of the urine sediment. The physical portion notes color, clarity, odor, and volume. The chemical portion uses a reagent strip to assess pH, specific gravity, protein, glucose, ketones, bilirubin, urobilinogen, nitrites, and leukocyte esterase; blood may also be reported. The microscopic portion examines the urine sediment for red and white blood cells, epithelial cells, bacteria, crystals, casts, and other elements.

Specimens are usually collected as a clean-catch midstream sample, though first-morning urine, catheterized samples, or suprapubic aspirates may be used in certain situations. Indications include evaluation of urinary symptoms (dysuria, frequency, hematuria), screening in otherwise healthy individuals, monitoring of known kidney or metabolic disorders, and preoperative assessment.

Interpretation requires clinical context and awareness of limitations. Contamination from vaginal secretions or improper collection can produce false positives. Hydration status, recent exercise, and menstruation may affect results. Positive nitrites or leukocyte esterase suggest bacterial infection; microscopic pyuria or bacteriuria supports infection but culture is often used to confirm. Normal values vary by laboratory, but most findings should be largely negative for protein, glucose, and blood, with few cells in the sediment.

Urinalysis is usually performed before more specific tests (such as urine culture) when infection or kidney disease is suspected, and results are integrated with history and examination.