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
, 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
. Cast 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.
Casts were first described by Henry Bence Jones
(1813-1873).Louis Rosenfeld, Four Centuries of Clinical Chemistry
, p.50, Gordon & Breach Science, 1999 ISBN 9056996452.
As reflected in their cylindrical form, casts 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 cast. "Cast" itself merely describes the shape, so an adjective
is added to describe the composition of the cast. Various casts found in urine sediment may be classified as follows.
The most common type of cast, hyaline... Read More