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White Blood Cell Casts, Urine

Published: August 9, 2026Updated: August 16, 2026

A urine microscopy test that looks for white blood cell casts, which can form when the kidney tubules are inflamed.

Quick summary

["White blood cell casts in urine may indicate inflammation or infection involving the kidneys."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
33228-8
Short code
WBC Casts #/area Ur Comp Assist
Synonyms
WBC Casts #/area 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 – 30 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 white blood cell casts. Casts are small structures formed inside kidney tubules and are seen with urine microscopy.

Why might I need this test?

A clinician may order this test to evaluate kidney inflammation, infection, or other conditions affecting the kidneys. It may be included as part of a urinalysis when blood or white blood cells are present in the urine.

How is the test performed?

A urine sample is collected and examined in the laboratory, typically with microscopy, to identify and count casts. The sample may also be evaluated for related findings, such as white blood cells, red blood cells, and protein.

How do I prepare for the test?

Usually, no special preparation is required. You will often be asked to provide a clean-catch urine sample, and the laboratory or clinician may give specific collection instructions.

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 WBC casts

Frequently asked questions

What are white blood cell casts?
They are tiny structures made of white blood cells and proteins that form inside kidney tubules. Finding them in urine suggests that the inflammation may involve the kidneys.
Does a positive result always mean I have a kidney infection?
No. White blood cell casts can be associated with infection, but they may also occur with other forms of kidney inflammation. Your clinician will interpret the result with the rest of your urinalysis and your symptoms.
How is the urine sample collected?
The sample is usually collected in a sterile container using a clean-catch technique. Follow any collection and timing instructions provided by the laboratory or clinician.
  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 16, 2026. · Read our editorial policy