There are many different types of urinary casts that can indicate important health information.
A urinary cast is a small tube-like structure sometimes found when urine is examined under a microscope. These structures can indicate problems with your kidneys, along with certain conditions and infections.
Sometimes, otherwise healthy people can develop temporary urinary casts as a result of dehydration.
Testing for urinary casts is done as part of a simple and noninvasive urine collection and urinalysis. There’s no risk or pain involved in this testing.
Several types of casts can be found in urine. The type of cast varies depending on the substances that make up that cast.
For instance, casts can be made of proteins, red blood cells, white blood cells, bacterial, and epithelial cells, fatty substances, and more. The makeup of casts is an indicator of their underlying cause and can help doctors use the casts to confirm a diagnosis.
The types of urinary casts include:
- Hyaline casts: Hyaline casts are made of a protein called uromodulin. They can be the result of every day and easily fixable conditions like dehydration or strenuous exercise, or chronic conditions like renal disease.
- Red blood cell (RBC) cast: RBC casts are composed of red blood cells. They’re red or orange-yellow in color and are typically found when people have conditions that cause kidney bleeding.
- White blood cell (WBC) casts: WBC casts are made up of white blood cells. Often, WBC casts are the result of infections that have reached the kidneys.
- Bacterial casts: Bacterial casts can also signal infection. Sometimes, a bacterial casts are found mixed in with WBC casts.
- Fatty casts: Fatty casts are made up of lipids. When lipids are present in the urine, it can be a sign of kidney dysfunction.
- Renal tubular epithelial casts: Renal tubular epithelial casts are composed of epithelial cells, like skin cells and the cells that line your organs. They can be caused by conditions that cause these cells to die off and clump.
- Pigment casts: Pigment casts are known for their colors. They’re often caused by taking medication and don’t typically indicate any conditions.
- Granular casts. Granular casts are similar to hyaline casts, but they’re associated with more cell breakdown and are more likely to result from chronic kidney disease.
- Waxy casts. Waxy casts are advanced granular casts with significant cell breakdown.
What is the most common type of cast seen in urine?
Hyaline casts are the most common type of cast seen in urine.
While most other casts are the result of serious infections or chronic diseases, these casts can be caused by dehydration and intense exercise.
This means they can be found in the urine of otherwise healthy people, making them much more common than other types of urinary casts.
The type of urinary cast found in testing can indicate a condition that can help doctors confirm a diagnosis. For instance, casts and their common diagnoses include:
- Hyaline casts: Dehydration or chronic kidney disease.
- RBC casts: Inflammation of the kidney’s filters (glomerulonephritis)
- WBC casts: Kidney inflammation or infection.
- Bacterial casts: Infections.
- Fatty casts: Too much protein in the urine (nephrotic syndrome), lupus, lipoid nephrosis.
- Renal tubular epithelial casts: Damage to kidney tubes.
- Granular casts: Urinary retention, urinary tract infections, chronic kidney disease.
- Waxy casts: Urinary retention, advanced kidney disease.
Often, testing for urinary casts will be just one part of the diagnostic process. You might also have bloodwork, imaging, or endoscopy to help confirm your diagnosis.
Your medical team will let you know your results along the way. The results of urinary cast testing can help rule out some conditions and point the way toward others.
A urinary cast is a tube-like structure that forms in urine as the result of conditions, infections, or problems with kidney function. Sometimes, temporary changes to your body’s normal state, like dehydration or an intense workout, can also cause urinary casts.
There are several types of urinary casts. The type of cast indicates the underlying cause. For example, the most common type of casts, hyaline casts, are typically the result of dehydration, exercise, or chronic kidney failure.
Testing for urinary casts is quick and painless and helps doctors confirm a diagnosis.