Urinary casts

Urinary casts are tiny tube-shaped particles that can be found when urine is examined under the microscope during a test called urinalysis. Urinary casts may be made up of white blood cells, red blood cells, kidney cells, or substances such as protein or fat. The content of a cast can help tell your health care provider whether your kidney is healthy or abnormal.

• Fatty casts are seen in people who have lipids in urine, usually as a complication of nephrotic syndrome. 
• Granular casts are a sign of many types of kidney diseases. 
• Hyaline casts are usually caused by dehydration. 
• Red blood cell casts mean there is a microscopic amount of bleeding from the kidney. They are seen in many kidney diseases. 
• Renal tubular epithelial cell casts reflect damage to tubule cells in the kidney. These casts are seen in conditions such as renal tubular necrosis, viral disease (such as CMV nephritis), and kidney transplant rejection. 
• Waxy casts can be found in people with advanced kidney disease and chronic kidney failure. 
• White blood cell (WBC) casts are more common with acute kidney infections.

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Urinary casts

Image 1: Urinary casts (phase contrast microscopy). (A), Hyaline cast; (B), hyaline-granular cast; (C), waxy cast; (D), erythrocyte cast, with erythrocytes (arrows) embedded in cast matrix; (E), hemoglobin cast; (F), leukocyte cast, showing large nuclei (arrows) characteristic of polymorphonuclear leukocytes.

Source: Medline Plus