Urinary casts are tiny tube-shaped particles that can be found when urine is examined under the microscope during a test called urinalysis. Urinary casts may be made up of white blood cells, red blood cells, kidney cells, or substances such as protein or fat.

Urine casts result from protein or other materials that conform to the shape of the distal tubules of the kidneys and then get excreted in the urine. They are seen using a microscope's low power field (LPF) during a urine examination (urinalysis) and often indicate kidney disease.

Urinary casts are microscopic cylindrical structures produced by the kidney and present in the urine in certain disease states. They form in the distal convoluted tubule and collecting ducts of nephrons, then dislodge and pass into the urine, where they can be detected by microscopy.