Red Blood Cell Casts per High-Power Field, Manual Microscopy (Urine Sediment)
This test counts red blood cell casts in a urine sediment sample under a microscope. Their presence can indicate bleeding or inflammation within the kidneys themselves.
["Finding red blood cell casts in urine suggests a kidney-related source of bleeding rather than a problem lower in the urinary tract."]
Key facts at a glance
- LOINC
- 74691-7
- Short code
- Rnd Cells #/area Smn HPF
- Synonyms
- Rnd Cells #/area Smn HPF
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- microscopy-light-hpf
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
What This Test Measures
A urine sample is concentrated by centrifugation, and the sediment is examined under a microscope. The laboratory reports the number of red blood cell casts seen per high-power field (HPF). A cast is a cylindrical structure formed in the kidney's tubules; when red blood cells become trapped in it, the result is a red blood cell cast.
Why It Is Ordered
Doctors order this test when they suspect bleeding or inflammation originating in the filtering units of the kidneys. It helps distinguish kidney disease from bleeding that comes from the bladder or other parts of the urinary tract.
How to Prepare
Usually no special preparation is needed. A clean-catch urine sample is typically collected. Follow any instructions your care team gives you about timing or collection.
What the Results Mean
The result is a count of red blood cell casts per high-power field. Even small numbers can be meaningful and are interpreted alongside your symptoms, other urine findings, and blood tests. Results are not interpreted as a standalone value, and reference ranges vary by laboratory.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Red blood cell casts are considered a marker of glomerular bleeding, meaning blood loss occurring within the kidney's filtering structures. They may be seen in conditions such as glomerulonephritis and other kidney disorders. Because findings depend on sample quality and observer technique, results should be evaluated by your clinician in the context of the full clinical picture.
Short name
RBC Casts /HPF
Frequently asked questions
What is a red blood cell cast?
Does finding red blood cell casts always mean kidney disease?
How is the urine sample collected?
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 16, 2026. · Read our editorial policy