Urinary 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 casts
• Granular casts
• Hyaline casts
• Red blood cell casts
• Renal tubular epithelial casts
• Waxy casts
• White blood cell casts

Your doctor may order this test to see if your kidneys are working properly and to check for certain conditions such as kidney infections, glomerular disease, and interstitial kidney disease.

A clean-catch (midstream) urine sample is needed, preferably the first morning urine sample. For information on how to collect this sample, see: Clean-catch urine culture

No special preparation is needed.

The test involves only normal urination, and there is no discomfort.