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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 tell your health care provider whether your urine is healthy or abnormal.

How the Test is Performed

The urine sample you provide may need to be from your first morning urine. The sample needs to be taken to the lab within 1 hour.

A clean-catch urine sample is needed. The clean-catch method is used to prevent germs from the penis or vagina from getting into a urine sample. To collect your urine, the health care provider may give you a special clean-catch kit that contains a cleansing solution and sterile wipes. Follow instructions exactly so that the results are accurate.

How to Prepare for the Test

No special preparation is needed.

How the Test Will Feel

The test involves only normal urination. There is no discomfort.

Why the Test is Performed

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

Normal Results

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 many types of kidney diseases.
  • Hyaline casts are usually caused by dehydration, exercise, or (water pills) diuretic medicines.
  • Red blood cell casts are a sign of bleeding into the kidney. They are seen in many kidney diseases.
  • Renal tubular epithelial cell casts reflect damage to cells in the kidney called tubule cells. 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 persons with advanced kidney disease and chronic kidney failure.
  • White blood cell (WBC) casts are more common with acute kidney infections.

Your health care provider will tell you more about your results.

Risks

There are no risks with this test.

Alternative Names

Hyaline casts; Granular casts; Renal tubular epithelial casts; Waxy casts; Casts in the urine; Fatty casts; Red blood cell casts; White blood cell casts

References

Gerber GS, Brendler CB. Evaluation of the urologic patient: history, physical examination, and urinalysis. In: Wein AJ, Kavoussi LR, Novick AC, et al., eds. Campbell-Walsh Urology. 10th ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 3.

McPherson RA, Ben-Ezra J. Basic examination of urine. In: McPherson RA, Pincus MR, eds. Henry’s Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 28.

Update Date: 8/18/2013

Updated 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, Bethanne Black, and the A.D.A.M. Editorial team.

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