A urinalysis is one of the oldest tests in medicine and still one of the most informative. A few milliliters of urine, examined properly, can reveal kidney inflammation, infection, stone risk, and protein loss — often before any blood test turns abnormal.
What we look for
The test has two parts. The dipstick screens chemically for protein, blood, glucose, nitrites, and white cells. The microscopic examination is where the real information lives: we spin the sample down and look at what settles out.
Red blood cells. Their shape matters enormously. Dysmorphic red cells — misshapen, with irregular membranes — indicate the blood came through the glomerulus, pointing toward glomerular disease. Normally shaped red cells suggest bleeding lower in the urinary tract: a stone, an infection, or something requiring urologic evaluation.
Casts. These are cylindrical molds formed in the kidney tubules. Red cell casts are essentially diagnostic of glomerulonephritis. White cell casts point to interstitial nephritis or pyelonephritis. Muddy brown granular casts appear in acute tubular necrosis.
Crystals. Calcium oxalate, uric acid, and cystine crystals each suggest a different stone-forming pathway and a different prevention strategy.
Protein. The dipstick detects albumin but misses light chains, which is why we order a separate albumin-to-creatinine ratio and, when myeloma is a consideration, a urine protein electrophoresis.
Why the microscopy matters
Many laboratories report only the dipstick. That is adequate for screening a healthy patient and inadequate for evaluating one with abnormal kidney function.
The difference between dysmorphic and normal red blood cells is the difference between a nephrology workup and a urology referral. The presence of red cell casts changes a case from unexplained hematuria to suspected glomerulonephritis — a different disease with a different urgency. That distinction cannot be made from a dipstick.
| Finding | What it can mean |
|---|---|
| Protein | Damage to the kidney's filters |
| Blood | Stones, infection, or a glomerular disease |
| Cells & casts | Point to where in the kidney the problem sits |
Collecting the sample
A clean-catch midstream sample. Begin urinating, stop, then collect. This reduces contamination from skin and genital flora, which otherwise produces false positives for white cells and bacteria.
A first-morning sample is most concentrated and therefore most sensitive. If you are menstruating, tell us — menstrual blood is a common and avoidable source of a falsely positive result.