10.2 Venous Reflux Examination Protocol & Cutoffs

Test reflux under safe, reproducible conditions

Venous reflux is sustained reverse flow caused by an incompetent valve or another abnormal pathway. A reflux examination must establish the vessel, source, extent, and duration of reversal. It differs from a thrombosis-only examination. A short reverse component during normal valve closure is not necessarily pathological, and color alone cannot provide an accurate duration.

Review symptoms, prior DVT, procedures, ulcers, pregnancy where relevant, mobility, and the clinical question. Assess for thrombus and define the deep and superficial anatomy before applying provocative maneuvers. The patient must be safe throughout the study. Do not place a person with orthostatic symptoms or inability to stand unsupported on a platform simply to obtain the textbook position.

Positioning

Standing is preferred when feasible because dependency fills the veins and provides a reproducible hydrostatic challenge. The examined leg is relaxed with weight mainly on the other leg, with stable support and fall prevention. Avoid muscle contraction that alters venous emptying. Record the actual position so follow-up measurements can be compared meaningfully.

When standing is unsafe or impossible, use an appropriate dependent alternative such as sitting or reverse Trendelenburg under the laboratory protocol. Document the modification and its limitations. A flat supine study can under-represent reflux and superficial diameter; it is not equivalent to a complete dependent reflux assessment. However, a rigid claim that every patient must tolerate a particular 45–60-degree table angle is inappropriate.

Provocation and timing

Distal compression followed by release produces antegrade augmentation and then challenges valve closure. Manual compression or a validated pneumatic system can be used. Choose the maneuver appropriate for the vessel and patient, keeping the transducer stable and the sample within the lumen. Standardize the technique; cuff pressure, release rate, and duration depend on the system/protocol rather than a single universal set of numbers.

A Valsalva maneuver can assess the common femoral vein and saphenofemoral junction. It is less reliable for more distal segments because intervening competent valves and variable effort limit pressure transmission. Distal compression/release is therefore used for the relevant more distal vessels. Confirm a technically adequate maneuver rather than interpreting a poor effort as a competent valve.

Record baseline forward flow and the induced reversal. In the IAC display convention, document forward flow below the baseline before the maneuver to establish that subsequent flow above it is reverse. The diagnostic concept is the direction relative to normal venous drainage, not red versus blue. Measure the sustained reverse interval on the spectral trace and exclude artifact or the antegrade augmentation spike.

Current vein-specific thresholds

The 2023 SVS/AVF/AVLS guideline defines reflux using the following durations:

The deep femoral vein is not the same vessel as the femoral vein. Do not apply “one second in every deep vein” indiscriminately. There is no minimum superficial truncal diameter required to diagnose reflux. A small truncal vein can be incompetent, and a large vein is not automatically incompetent.

For a pathologic perforator in CEAP C2, the guideline describes outward flow >0.5 seconds and diameter >3.5 mm. Other clinical contexts and source definitions need explicit attribution. The older 0.35-second rule should not be presented as the current universal perforator standard. Diameter and outward flow are findings, not an automatic order for perforator ablation.

Follow the anatomy and source

Evaluate the common femoral and femoral veins, popliteal vein, junctions, great saphenous vein, small saphenous vein, and relevant accessory/tributary/perforator pathways. Trace superficial reflux to its source, which can be a junction, tributary, perforator, or pelvic-origin pathway. A varicose surface vein does not establish that the great saphenous trunk is the source.

Measure diameters with minimal pressure at named sites and in the recorded dependent position. Identify the saphenous compartment and distinguish the trunk from adjacent tributaries. The small saphenous termination and cranial extension vary; do not assume every patient has the same popliteal junction. Map treated, absent, thrombosed, or recanalized segments rather than describing them as ordinary native anatomy.

Worked interpretations

A standing great saphenous vein has reverse flow for 0.8 seconds after adequate distal release. This exceeds the superficial truncal threshold. A common femoral vein with the same 0.8-second reverse interval does not meet the >1-second criterion. The same number has different meaning in different vessels.

A deep femoral vein has 0.7 seconds of reversal. Under the current guideline, the >0.5-second threshold applies, so it supports reflux. Calling it normal because it is “deep and under one second” would confuse deep femoral with femoral criteria.

A 4.0 mm perforator has outward flow lasting 0.6 seconds in a patient with C2 disease. These findings meet the described pathologic-perforator definition for that context. Report location and relationship to the clinical findings; the treatment decision remains individualized.

Report the examination, not just a positive label

Include position, maneuvers, veins tested, reflux durations, diameter sites, source/extent, thrombotic or post-thrombotic findings, prior procedures, and limitations. Explain why an examination was incomplete when a patient could not tolerate the intended position or maneuver. Precise anatomy and technique make results more useful for treatment planning and future comparison than an isolated “reflux present.”

2023 SVS/AVF/AVLS varicose-vein guideline and IAC standards, August 2026 — checked October 18, 2026.