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Red Blood Cell Casts, Urine, Qualitative — Computer-Assisted Microscopy

Published: August 9, 2026Updated: August 17, 2026

A urine test that looks for red blood cell casts, which can indicate bleeding or inflammation within the kidneys.

Quick summary

["Red blood cell casts in urine may suggest kidney inflammation, injury, or bleeding and should be interpreted with other kidney test results."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
53278-8
Short code
RBC Casts Ur Ql Comp Assist
Synonyms
RBC Casts Ur Ql 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 urine for red blood cell casts. Casts are structures formed in the kidney's tiny filtering tubules, and they can help identify problems affecting the kidneys.

Why might I need this test?

Your clinician may order this test if your urine contains blood or red blood cells, or if you have symptoms suggesting a kidney problem, such as swelling, back pain, or changes in urination.

How is the test performed?

A urine specimen is examined under a microscope, with computer-assisted image analysis sometimes used to help identify casts. The result is generally reported as present or absent.

How do I prepare for the test?

Follow your clinician or laboratory's collection instructions. Urine is often collected as a clean-catch sample in a sterile container, and the timing of collection may vary.

Reference range

Adult: 10-40 U/LN/A

Specimen: urine

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Urine RBC Casts

Frequently asked questions

What does an RBC cast mean?
An RBC cast is a microscopic structure made of red blood cells and protein that forms in the kidney's filtering tubules. Its presence can suggest inflammation or injury within the kidneys.
Does finding RBC casts confirm a specific kidney disease?
No. RBC casts can occur with several kidney conditions, so the result must be considered with other urine findings, kidney tests, symptoms, and your medical history.
Does this test require fasting?
Fasting is generally not required for urine cast testing. Follow any specific collection and timing instructions provided by your clinician or laboratory.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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