DefinitionUrinary casts are tiny tube-shaped particles made up of white blood cells, red blood cells, or kidney cells. They form in kidney structures called tubules. Casts are held together by a protein released by the kidney. The content of a cast can tell your health care provider whether your urine is healthy or abnormal.Types of urinary casts include:Fatty castsGranular castsHyaline castsRed blood cell castsRenal tubular epithelial castsWaxy castsWhite blood cell castsAlternative NamesHyaline casts; Granular casts; Renal tubular epithelial casts; Waxy casts; Casts in the urine; Fatty casts; Red blood cell casts; White blood cell castsHow the test is performedA clean-catch (midstream) urine sample is needed, preferably the first morning urine sample. For information on how to collect th