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Fatty Casts, Urine — Microscopic Examination (per High-Power Field)

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

This urine microscopy test looks for fatty casts, which are urinary structures containing fat or fatty acids. Their presence can be associated with conditions that cause heavy urinary fat loss, especially nephrotic syndrome.

Quick summary

["Fatty casts in urine may indicate kidney disease associated with heavy protein loss."]

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

Key facts at a glance

LOINC
67813-6
Short code
Fatty Casts #/area UrnS HPF
Synonyms
Fatty Casts #/area UrnS HPF
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-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 identify and count fatty casts. Fatty casts are tube-shaped urinary structures that contain fat or fatty acids, and the result may be reported per high-power field viewed.

Why might I need this test?

A clinician may order this test as part of a urinalysis when evaluating kidney symptoms, swelling, or unexplained protein in the urine. Fatty casts can be found in disorders that cause the kidneys to lose substantial protein and other substances into the urine.

How is the test performed?

A urine specimen is collected and examined under a microscope. The laboratory looks for characteristic fatty casts and may report the number seen per high-power field.

How do I prepare for the test?

Follow the collection instructions provided by your healthcare professional. A clean-catch urine sample is often requested, and the laboratory or clinician will tell you when and how to submit the specimen.

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

Urine Fatty Casts

Frequently asked questions

What are fatty casts?
Fatty casts are microscopic, tube-shaped structures in the urine that contain fat or fatty acids. They are commonly formed when lipid-containing material becomes trapped inside a renal tubule cast.
What can cause fatty casts in urine?
They are most often associated with kidney disorders that cause substantial protein loss, particularly nephrotic syndrome. Other conditions affecting the kidneys can also produce them.
Does a positive result confirm a specific disease?
No. Fatty casts support evaluation for certain kidney conditions but must be interpreted alongside other laboratory results, symptoms, and clinical findings.
  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