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Fatty Casts, Urine — Qualitative Microscopy

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

A urine microscopy test that checks for fatty casts, which can occur when the kidney tubules are affected by certain conditions.

Quick summary

["Fatty casts in urine may suggest kidney tubular injury, especially when accompanied by heavy protein loss."]

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

Key facts at a glance

LOINC
25159-5
Short code
Fatty Casts UrnS Ql Micro
Synonyms
Fatty Casts UrnS Ql Micro
Category
liver
Sample
urine
Container
Sterile urine container
Units
N/A
Ref low
10
Ref high
40
Critical range
— – 500 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
microscopy-light
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 urine test uses microscopy to look for fatty casts. Casts are structures that form inside kidney tubules and are released into the urine. Fatty casts contain fat or fat-like material.

Why might I need this test?

Your clinician may order this test when urine tests show protein, blood, or other signs that may point to kidney or kidney tubular disease. It can also help assess suspected conditions associated with abnormal fat or protein handling by the kidneys.

How is the test performed?

A urine sample is examined under a microscope to identify casts and assess whether they contain fatty material. The result is generally reported as present or absent. A fresh, uncontaminated urine specimen is important for accurate interpretation.

How do I prepare for the test?

Follow your clinician's or laboratory's urine-collection instructions. In many cases, a clean-catch midstream sample is requested, and the sample should be analyzed promptly. Ask the laboratory whether a first-morning specimen is preferred.

Reference range

Adult: 10-40 U/LN/A

Specimen: urine

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Urinary Fatty Casts

Frequently asked questions

What does a positive result mean?
Fatty casts were identified in the urine. This may suggest that the kidney tubules are not functioning normally, but other urine and blood test findings are needed to determine the cause.
Is this the same as a urine lipid test?
No. This test looks for fatty casts under a microscope; it does not directly measure the amount of fat in the urine.
Does one abnormal result confirm kidney disease?
No. Fatty casts can have several causes and may be temporary. Your clinician will interpret them alongside symptoms, repeat testing when appropriate, and other kidney function results.
  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