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Urinary measurement of renal pelvis diameter (24-hour fluid collection)

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

This test measures the size of your kidney’s upper collecting tube (renal pelvis) over a 24-hour period using urine collected from your bladder.

Quick summary

["This test helps assess kidney function and fluid balance by tracking changes in urine volume and structure over time."]

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

Key facts at a glance

LOINC
11811-7
Short code
Renal pelvis-R Diam US.meas
Synonyms
Renal pelvis-R Diam US.meas
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
44
Ref high
147
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
us-measured
CPT
84075
SNOMED
27550007
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why This Test Is Done

Your doctor may order this test to evaluate conditions affecting kidney drainage, such as blockages, infections, or structural abnormalities. It can also help diagnose or monitor kidney diseases, fluid retention, or urinary tract issues by observing how urine flows and accumulates in the renal pelvis.

What to Expect Before the Test

You’ll need to collect all urine for 24 hours in a special container. Drink regular fluids as directed, avoid diuretics (like caffeine), and follow any specific instructions your lab provides to ensure accurate results.

During the Test

No special preparation is needed beyond urine collection. The test involves measuring the volume and characteristics of urine over time, often analyzed via lab techniques like nephelometry or turbidimetry to assess renal pelvis dilation.

What the Results Mean

Results may indicate whether fluid is draining properly from your kidneys. Abnormal findings could suggest conditions like hydronephrosis (swelling from blockage), kidney stones, or other structural issues requiring further evaluation.

Reference range

Adult: 44-147 U/LN/A

Specimen: serum

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

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Frequently asked questions

How often should I expect this test?
This test is typically done once or occasionally as part of a diagnostic workup. Frequency depends on your symptoms, medical history, or doctor’s recommendations.
What are the normal results?
There are no standard numeric ranges for this test since it measures qualitative changes in urine volume and structure. Your doctor will interpret results based on clinical context and your specific health needs.
Can I take medications before this test?
Yes, but avoid diuretics (like caffeine or certain medications) unless instructed otherwise. Always check with your doctor or lab staff before taking any medications.
  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