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How venous valves and reflux work

Blood in the legs travels against gravity to return to the heart. Calf-muscle movement and small venous valves help it move upward.

How venous valves and reflux work
Original medical illustration | Dr LiangVascular

Clinical Education

When a valve does not close properly, blood flows backward. Pressure builds and the vein may enlarge and twist.

  • Valves act like one-way doors
  • Poor closure allows backward flow, called reflux
  • Ultrasound is used to locate reflux

How healthy valves work

  • Walking activates the calf-muscle pump and pushes blood upward.
  • Valves open to let blood pass, then close to prevent backward flow.

What happens when a valve leaks?

  • Blood repeatedly flows backward and increases pressure.
  • Superficial veins gradually enlarge and twist.
  • Heaviness, aching or swelling may worsen after standing.

Normal return and venous reflux

ComparisonNormal returnVenous reflux
ValveCloses properlyDoes not close completely
Blood directionToward the heartPartly flows downward
PressureMore stableGradually increases
ResultVein remains more normalVaricose veins may develop

Note: Appearance alone cannot show where reflux begins. Standing leg-vein ultrasound can clarify the cause.

References

  1. De Maeseneer MG, et al. ESVS 2022 Clinical Practice Guidelines. Eur J Vasc Endovasc Surg. 2022;63:184–267. View source

Related Clinical Education

This article is for health education only and does not replace individual medical assessment. Seek urgent care for acute symptoms.

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Begin with a careful assessment.

Symptoms, examination and ultrasound findings are considered before treatment options are discussed.

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Website content is for medical education only and does not replace individual diagnosis or medical advice.

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