Venous Reflux of the Lower Extremities: Provocative Tests, Pathological Reflux Thresholds, and Valve Assessment
Essence of the Method
If thrombosis is about patency, then reflux is about valve function. Incompetent valves allow blood to flow retrograde, and under the influence of gravity, chronic venous insufficiency develops: from varicose veins and edema to trophic ulcers. The main task of duplex ultrasound is not just to visualize reflux but to provoke it correctly (without provocation, an incompetent valve may go unnoticed), measure the duration of retrograde flow, determine the source, and describe the finding in the language of the CEAP classification.
Patient Position and Technique
Reflux is assessed while standing on a venous platform (weight on the healthy leg) or sitting with legs dangling; lying down is unacceptable. The sample volume is set 1–2 cm distal to the valve, correction angle <60°, low filter is used. Linear transducer 7–12 MHz.
Provocative Tests
The entire superficial venous system is examined starting with the SFJ using the Valsalva maneuver and manual distal compression. By segments:
- SFJ — Valsalva maneuver (assessment of the terminal valve);
- Trunks, tributaries, perforators — distal compression with release (distal augmentation).
Parana maneuver — measurement of venous flow in stress tests with calculation of the dynamic reflux index; simple, reproducible, no equipment required.
Pathological Reflux Thresholds (SVS/AVF, International Consensus)
Reflux is measured as the duration of retrograde flow from the onset to cessation after provocation.
| Vein | Pathological Reflux Threshold |
|---|---|
| Superficial (GSV, SSV, ASV) and tributaries | >0.5 s |
| Perforators | >0.5 s (in some documents 0.35–0.5 s) |
| Tibial and deep femoral vein | >0.5 s |
| Femoral and popliteal (deep main) | >1.0 s |
Incompetent Perforator
Determined by a combination of signs: diameter >3.5 mm at rest, outward (from deep to superficial) reflux >0.5 s, and — for "pathological" by SVS/AVF — location under a healed or open ulcer (class C5–C6).
Example Description
A strong conclusion contains the duration of reflux with indication of the test for each segment, source, condition of the deep system, and final CEAP formula. Example: left GSV in the saphenous compartment — diameter 6.9 mm (mid-thigh), 10.2 mm (knee level), trunk dilation; reflux 1.1 s (standing, distal augmentation). SFJ — Valsalva maneuver, reflux 0.7 s (terminal valve incompetence). Anterior accessory saphenous vein (ASV): diameter 3.0 mm, own "saphenous eye," no reflux (healthy trunk). Specify vein depth <5 mm separately for thermal ablation.
Additional Plethysmographic Indicators
In photoplethysmography/air plethysmography, use: PPG VRT <20 s; APG FT <25 s; FR >2 ml/s; RV >20–35%. FT shorter than 10 s indicates severe reflux, shorter than 25 s indicates mild-moderate. FR >2 ml/s indicates venous insufficiency; RV% >20–35% is associated with increased ambulatory venous pressure.
Frequently asked questions
Why can't reflux be assessed lying down?
Lying down is unacceptable. Reflux is assessed standing on a venous platform with weight on the healthy leg or sitting with legs dangling.
Which test is used for the SFJ and which for the trunks?
For the SFJ — Valsalva maneuver (assessment of the terminal valve), for trunks, tributaries, and perforators — distal compression with release (distal augmentation).
What is the reflux threshold for deep main veins?
For femoral and popliteal veins, the pathological reflux threshold is >1.0 s; for tibial and deep femoral vein — >0.5 s (SVS/AVF).
How to determine an incompetent perforator?
By a combination of: diameter >3.5 mm at rest, outward reflux >0.5 s, and location under a healed or open ulcer (C5–C6) — for "pathological" by SVS/AVF.
What technical parameters are important when measuring reflux?
Sample volume 1–2 cm distal to the valve, angle <60°, low filter, transducer 7–12 MHz, vertical patient position.