Urinary cast
![Micrograph showing casts in a kidney biopsy. Hyaline casts are PAS positive (dark pink/red - right of image). Myelomatous casts are PAS negative (pale pink - left of image). PAS stain.](/Images/godic/202502/19/Cast_nephropathy_-_2_cropped_-_very_high_mag2409.jpg")
Urinary casts are 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.