Urine Granular Casts
Granular casts are tube-shaped structures from the kidney tubules that have a coarse, grainy texture, often from the breakdown of cells or protein trapped inside them.
A small number can follow heavy exercise or dehydration and be harmless. In larger numbers, or with other abnormal findings, granular casts can be a clue to kidney tubule injury and deserve a closer look.
More granular casts, especially the darker 'muddy brown' type, can point toward damage to the kidney tubules, sometimes from reduced blood flow, certain medications, or other kidney conditions. This finding is usually followed up with additional kidney tests.
Absence of granular casts is the expected, reassuring finding.
None to occasional granular casts can be normal, particularly after exertion. Your clinician weighs them against kidney blood tests and your overall situation before drawing conclusions.
Sources
Educational context only, not medical advice or a diagnosis. Reference ranges vary by lab, age and sex; always discuss your results with a clinician.