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Doppler Ultrasound — Maximum Velocity, Diameter, and S/D Ratio

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

A Doppler ultrasound measures blood-flow speed and the diameter of a vessel or valve. This code also indicates a systolic-to-diastolic flow ratio.

Quick summary

["The results can help clinicians assess blood flow, narrowing, and resistance within the examined vessel or heart valve."]

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

Key facts at a glance

LOINC
29424-9
Short code
PV-LU Vmax dias DOP
Synonyms
PV-LU Vmax dias DOP
Category
liver
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
us-doppler
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

What is this test?

Doppler ultrasound uses sound waves to measure the speed and pattern of blood flow. The maximum velocity, structure diameter, and systolic-to-diastolic ratio help evaluate blood flow through a blood vessel or heart valve.

Why might I need this test?

This test may be used to investigate suspected narrowing, reduced blood flow, abnormal valve function, or changes in blood-flow resistance. It is often performed as part of a vascular or heart ultrasound examination.

How is the test performed?

A technician places an ultrasound probe over the area being examined. The machine uses Doppler technology to display and measure blood-flow velocity, while ultrasound images are used to measure the diameter of the vessel or valve opening.

How do I prepare for the test?

Doppler ultrasound usually requires little or no preparation unless the imaging center provides specific instructions. You may be asked to lie still and may need to temporarily remove clothing, jewelry, or other items near the examination area.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Doppler flow measurement

Frequently asked questions

Is this test the same as a standard ultrasound?
It is usually part of an ultrasound examination. Standard images show anatomy, while Doppler technology measures the speed and pattern of blood flow.
What does the S/D ratio mean?
The S/D ratio compares the blood-flow velocity during the heart's contraction phase with the velocity during relaxation. It can provide information about resistance to blood flow.
Will I need to have blood drawn?
No. Doppler ultrasound does not require a blood sample and is performed using sound waves applied to the skin.
  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