Urine Sediment: Cells, Casts, and the Source of Hematuria

Formed elements localize injury

Urine microscopy can reveal red and white cells, tubular cells, casts, and crystals. These findings connect laboratory abnormalities to possible sites of injury, but collection, sample age, technique, and observer expertise affect reliability.

Recognize a glomerular pattern

Acanthocytes and red cell casts support glomerular bleeding, especially with proteinuria or declining kidney function. Isomorphic red cells can occur in urologic disease, but morphology is not an infallible exclusion test for glomerular pathology.

Assess the full sediment

Granular casts and tubular epithelial cells support tubular injury; white cell findings have inflammatory or infectious differentials. Crystals may be incidental or clinically important depending on type, pH, medication exposure, and the clinical setting.

Integrate and escalate

Combine microscopy with protein quantification, creatinine trend, BP, symptoms, and systemic findings. Rapid renal deterioration or a pulmonary–renal presentation warrants urgent specialist assessment; persistent hematuria also requires an appropriate urologic or nephrologic evaluation.

Use the right technique

Prompt processing and a trained examination improve interpretation. Phase contrast can help evaluate red cell morphology, and polarized light can assist with selected crystals or lipids. Automated reports may need manual review when the question is important.

Avoid absolute language

An absent cast does not exclude disease, and an unusual structure can be misidentified. Do not call every red cell cast universally pathognomonic or infer a precise diagnosis solely from a percent-dysmorphism threshold.

Self-check: A heme-positive strip and a red cell cast answer different questions. Explain what each suggests and which specimen or clinical limitations matter.