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White Blood Cell Casts, Urine — Qualitative Microscopy

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

A urine microscopy test that checks for white blood cell casts, which may form when inflammation involves the kidneys.

Quick summary

["White blood cell casts in urine can suggest inflammation or infection in the kidneys, particularly pyelonephritis."]

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

Key facts at a glance

LOINC
107174-5
Short code
WBC Casts # UrnS Comp Assist
Synonyms
WBC Casts # UrnS 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 under a microscope to look for white blood cell casts. These casts are tiny structures that form in the kidney's small urine-producing tubes 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 urinary symptoms such as painful or frequent urination, fever, flank pain, or unexplained changes in urine. They can also be included as part of a routine urinalysis.

How is the test performed?

A urine specimen is collected and prepared for microscopic analysis. A laboratory professional examines the urine sediment to identify and report the presence or absence of white blood cell casts.

How do I prepare for the test?

Follow the collection instructions provided by your healthcare professional. Often, a clean-catch midstream urine sample is requested, and the sample should be delivered promptly so that cells and casts remain identifiable.

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 small structures made of white blood cells and protein that form inside the kidney's urine-producing tubules. Finding them in urine suggests that the kidneys or urinary tract may be inflamed.
Does this test diagnose a kidney infection by itself?
No. White blood cell casts can support concern for a kidney infection, but a clinician must interpret them along with symptoms, physical examination findings, and other urine or blood tests.
Can anything other than infection cause white blood cell casts?
Yes. Inflammatory kidney conditions, including some forms of interstitial nephritis, may also produce them. The result is therefore best reviewed in clinical context.
  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