Which urine sediment finding is most characteristic of glomerulonephritis?

• A. Eosinophils
• B. Epithelial cell casts
• C. White blood cell casts
• D. Red blood cell casts

Answer: (D)

In glomerulonephritis, inflammation of the kidney’s filtering units causes bleeding from the glomeruli into the tubular system. Red blood cells leak into the nephrons, and as they pass through the tubules they get trapped in a proteinaceous matrix to form red blood cell casts. This sediment finding—blood cells within casts—directly reflects glomerular bleeding and is highly characteristic of glomerular disease.

Other sediment findings point to different processes: eosinophils in the urine suggest allergic interstitial nephritis; epithelial cell casts indicate tubular injury or necrosis; white blood cell casts are more typical of tubulointerstitial inflammation such as pyelonephritis or interstitial nephritis. While white blood cell casts can occur in glomerulonephritis, the presence of red blood cell casts best signals glomerular involvement.