Red Blood Cell Casts, Urine — Computer-Assisted Microscopy
A urine microscopy test that detects red blood cell casts, which may help evaluate inflammation or bleeding within the kidneys.
["Red blood cell casts in urine can be a sign of inflammation or bleeding in the kidneys and should be interpreted with other test results."]
Key facts at a glance
- LOINC
- 53285-3
- Short code
- RBC Casts # Ur Comp Assist
- Synonyms
- RBC Casts # Ur Comp Assist
- Category
- liver
- Sample
- urine
- Container
- Sterile urine container
- Units
- N/A
- Ref low
- 10
- Ref high
- 40
- Critical range
- 2 N/A – 7 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- computer-assisted
- CPT
- 84484
- SNOMED
- 302774002
- Specimen volume
- 10 mL
- Stability
- Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
What is this test?
This test examines a urine sample for red blood cell casts. These are red blood cells trapped in a protein-like material formed inside the kidney tubules.
Why might I need this test?
Urine red blood cell casts may be checked when there are blood in the urine, kidney symptoms, or concerns about kidney inflammation. They are one of several findings doctors use to evaluate the source and cause of kidney-related blood or protein leakage.
How is the test performed?
A urine sample is collected and examined with computer-assisted microscopy. The laboratory looks for the characteristic shape of red blood cell casts and reports whether they are present.
How do I prepare for the test?
Follow the laboratory's urine collection instructions, which may include a clean-catch, first-morning, or timed collection. Tell the healthcare provider if you have recently exercised intensely, taken medicines, or had a urinary tract infection.
Reference range
Adult: 10-40 U/LN/A
No special preparation required. Stay well hydrated.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Finding red blood cell casts may suggest that blood is coming from the kidney rather than the lower urinary tract, particularly when they occur with protein in the urine. Possible causes include inflammation of the kidney filters, infection, or certain vascular conditions. Results must be interpreted with symptoms, urine protein findings, kidney function tests, and the other elements of the urinalysis.
Short name
Urine Red Blood Cell Casts
Frequently asked questions
What are red blood cell casts?
Does a positive result mean I have a kidney disease?
Can exercise affect the result?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy