Micrograph showing<unk> s in a kidney biopsy using PAS stain. Hyaline<unk> s are PAS-positive (dark pink/red, right of image). Myelomatous<unk> s are PAS-negative (pale pink, left of image)<unk> s 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. They form via precipitation of Tamm–Horsfall mucoprotein which is secreted by renal tubule cells, and sometimes also by albumin in conditions of proteinuria.<unk>  formation is pronounced in environments favoring protein denaturation and precipitation (low flow, concentrated salts, low pH). Tamm–Horsfall protein is particularly susceptible to precipitation in these conditions.<unk> s were first described by Henry Bence Jones (1813–1873). As reflected in their cylindrical form,<unk> s are generated in the small distal convoluted tubules and collecting ducts of the kidney, and generally maintain their shape and composition as they pass through the urinary system. Although the most common forms are benign, others indicate disease. All rely on the inclusion or adhesion of various elements on a mucoprotein base—the hyaline<unk> . "Cast" itself merely describes the shape, so an adjective is added to describe the composition of the<unk> . Various<unk> s found in urine sediment may be classified as follows.
Urinary cast
Cystography
Ureteroscopy
Cystometry
Cystoscopy
Urine cytology
Urinary tract ultrasound
Uroscopy