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.
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
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.
The test involves only normal urination. There is no discomfort.
Why the Test is Performed
Your provider may order this test to see if your kidneys are working properly. It may also be ordered to check for certain conditions, such as:
There are different types of casts. The presence of a few hyaline casts is normal.
The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.
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.
- 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.
Your provider will tell you more about your results.
There are no risks with this test.
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.
Reviewed By: Laura J. Martin, MD, MPH, ABIM Board Certified in Internal Medicine and Hospice and Palliative Medicine, Atlanta, GA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.