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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
Hyaline casts; Granular casts; Renal tubular epithelial casts; Waxy casts; Casts in the urine; Fatty casts; Red blood cell casts; White blood cell casts
How the Test is Performed
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
How to Prepare for the Test
No special preparation is needed.
How the Test Will Feel
The test involves only normal urination, and there is no discomfort.
Why the Test is Performed
There are different types of casts. The presence of a few hyaline casts is normal.
What Abnormal Results Mean
Abnormal results may include:
- Fatty casts are seen in people who have lipids in urine, usually as a complication of nephrotic syndrome.
- Granular casts are a sign of underlying kidney disease. However, they are nonspecific and may be found in people with many different kidney disorders.
- Hyaline casts are usually caused by dehydration, exercise, or diuretic medicines.
- Red blood cell casts are a sign of bleeding into the kidney tubule. They are seen in many diseases affecting the glomerulus, including IgA nephropathy, lupus nephritis, Goodpasture syndrome, and Wegener's granulomatosis.
- Renal tubular epithelial cell casts reflect damage to the tubule cells. They are seen in renal tubular necrosis, viral disease (such as CMV nephritis), and kidney transplant rejection.
- Waxy casts are associated with advanced kidney disease and chronic kidney failure.
- White blood cell (WBC) casts are more common in interstitial cell kidney diseases such as interstitial inflammation, pyelonephritis, and parenchymal infection.
This test may also show:
Landry DW, Bazari H. Approach to the patient with renal disease. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 116.
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.