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Fatty Casts, Urine — Microscopic Examination

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

A urine microscopy test that looks for fatty casts, which contain lipid droplets and may be associated with disorders of kidney filtering.

Quick summary

["Fatty casts in urine can be a sign of significant kidney disease, especially when protein is also being lost in the urine."]

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

Key facts at a glance

LOINC
5789-3
Short code
Fatty Casts #/area UrnS LPF
Synonyms
Fatty Casts #/area UrnS LPF
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-lpf
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 fatty casts. Casts are structures that form inside the kidney's filtering tubules; fatty casts contain lipid droplets.

Why might I need this test?

Urine fatty casts may be checked when a clinician is evaluating kidney disease, especially if the urine contains an abnormal amount of protein. They may also be found during follow-up of conditions that affect kidney filtering.

How is the test performed?

A laboratory staff member prepares the urine sediment and examines it by microscopy. The report may describe the amount or area of fatty casts observed, depending on the laboratory's method.

How do I prepare for the test?

Collect urine in the container provided and follow the laboratory's collection instructions. A clean-catch, midstream urine sample is often requested, and the sample should be delivered promptly or refrigerated if instructed.

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

Are fatty casts in urine the same as fat in the urine?
No. Fatty casts are tube-shaped structures formed in the kidney that contain fat droplets, rather than simply showing free fat in the urine.
Does finding fatty casts confirm a specific kidney disease?
No. Fatty casts can occur with several kidney conditions and are often evaluated together with protein loss and other kidney test results.
Can this test be performed at home?
The specimen may be collected at home in some situations, but it must be examined by a laboratory using microscopy. Follow the collection and storage instructions provided by your healthcare team.
  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