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White Blood Cell Casts, Urine — Microscopic Examination (per High-Power Field)

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

Counts white blood cell casts in urine sediment under a microscope, reported per high-power field (HPF).

Quick summary

["White blood cell casts in urine can be a sign of inflammation or infection within the kidneys."]

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

Key facts at a glance

LOINC
49103-5
Short code
WBC Casts #/area UrnS HPF
Synonyms
WBC Casts #/area UrnS HPF
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
microscopy-light-hpf
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 under a microscope to look for white blood cell casts. Casts are structures that form inside kidney tubules and are released into the urine.

Why might I need this test?

Urine white blood cell casts may be checked when a clinician is evaluating kidney inflammation, a urinary tract infection, or possible kidney infection. They are usually interpreted along with urine protein, blood, culture, and other kidney test results.

How is the test performed?

A urine sample is collected and processed in the laboratory. The sediment is examined under a microscope, and the number of white blood cell casts is reported per high-power field.

How do I prepare for the test?

Collect the urine in the container provided by the laboratory, following its instructions. A clean-catch midstream sample is usually preferred, and the specimen should be delivered promptly.

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.

White blood cell casts may indicate inflammation within the kidney tubules, which can occur with conditions such as interstitial nephritis or pyelonephritis. Their presence may support a urinary tract or kidney infection, particularly when other urinalysis findings are abnormal. Results must be interpreted with symptoms and the rest of the laboratory evaluation because other conditions can also cause them.

Short name

Urine WBC casts

Frequently asked questions

What are white blood cell casts?
They are small structures made of white blood cells that form inside kidney tubules and then pass into the urine.
Do white blood cell casts always mean I have a kidney infection?
No. They most often suggest kidney inflammation but can occur with several conditions, so the result should be reviewed with a clinician.
Does this test use a blood sample?
No. This is a urine microscopy test performed on a urine specimen.
  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