Urinary casts are tube-shaped particles made up of white blood cells, red blood cells, and kidney cells. They develop 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

A clean-catch (midstream) urine sample is needed, preferably the first morning urine sample.

Men or boys should first wipe clean the head of the penis. Women or girls need to wash the area between the lips of the vagina with soapy water and rinse well.

As you start to urinate, allow a small amount to fall into the toilet bowl (this clears the urethra of contaminants). Then, in a clean container, catch about 1 to 2 ounces of urine and remove the container from the urine stream. Give the container to the health care provider or assistant.

In infants, thoroughly wash the area around the urethra. Open a urine collection bag (a plastic bag with an adhesive paper on one end), and place it on your infant. For boys, the entire penis can be placed in the bag and the adhesive attached to the skin. For girls, the bag is placed over the labia. Place a diaper over the infant (bag and all).

Check your baby frequently and remove the bag after the infant has urinated into it. For active infants, this procedure may take a couple of attempts -- lively infants can displace the bag. The urine is drained into a container for transport back to the health care provider.

No special preparation is needed.

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

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.

There are different types of casts. The presence of a few hyaline casts is normal.

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 tubules. They are seen in renal tubular necrosis, viral disease (such as CMV nephritis), and 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:

• Acute nephritic syndrome
• Glomerulonephritis - chronic
• Glomerulonephritis - post-streptococcal
• Glomerulonephritis - rapidly progressive
• Complicated urinary tract infection
• Necrotizing vasculitis
• Rhabdomyolysis
• Primary amyloid
• Secondary amyloid
• Systemic lupus erythematosus

There are no risks.