Left Small Saphenous Vein Ablation is NOT Medically Necessary
The requested left small saphenous vein ablation (CPT 36475,36476) does not meet medical necessity criteria because the vein diameter measurements (1.3-1.7mm) fall significantly below the required 4.5mm threshold for endovenous thermal ablation, regardless of reflux duration or symptom severity. 1, 2
Critical Size Threshold Not Met
The left small saphenous vein measurements documented on the 09/23/2025 duplex ultrasound are:
- Proximal: 1.3mm
- Mid: 1.5mm
- Distal: 1.7mm
All measurements are dramatically below the 4.5mm minimum diameter required for endovenous thermal ablation. 1, 2, 3 The American College of Phlebology and American Academy of Family Physicians explicitly state that veins must measure at least 4.5mm in diameter for endovenous ablation to be medically necessary and technically appropriate. 1, 2, 3
Why Size Matters
Treating veins below the 4.5mm threshold with thermal ablation leads to suboptimal outcomes and unnecessary procedural risks, including approximately 7% risk of nerve damage from thermal injury. 1, 3 The evidence demonstrates that endovenous thermal ablation achieves occlusion rates of 91-100% within one year only for appropriately sized veins (≥4.5mm). 4, 3, 5
Reflux Duration Criteria Met But Insufficient Alone
While the left proximal SSV demonstrates severe reflux (4100ms), reflux duration alone does not justify thermal ablation when vein diameter is inadequate. 1, 2 Both criteria must be met simultaneously: reflux ≥500ms AND diameter ≥4.5mm. 1
Duplex Timing Requirement Met
The 09/23/2025 duplex ultrasound is within the required 6-month timeframe for the 11/01/2025 procedure date, satisfying this criterion. 1
Appropriate Alternative Treatment
For veins measuring 2.5-4.4mm with documented reflux, sclerotherapy (foam or liquid) is the medically appropriate treatment option rather than endovenous thermal ablation. 2, 3 However, the left SSV measurements (1.3-1.7mm) fall below even the 2.5mm threshold typically considered for sclerotherapy. 2
For veins less than 2.5mm in diameter, conservative management with medical-grade compression stockings (≥20mmHg) and lifestyle modifications remains the recommended approach. 2
Clinical Context Considerations
The patient has already undergone successful treatment of larger veins:
- Right GSV ablation (previously measured at adequate diameter)
- The right distal SSV shows severe reflux and may warrant evaluation for treatment if diameter criteria are met
The left SSV, despite causing symptoms, is simply too small for safe and effective thermal ablation. 1, 2, 3
Common Pitfall to Avoid
Do not confuse reflux severity or symptom intensity with anatomic suitability for thermal ablation. 1, 2 The 4.5mm diameter threshold exists because smaller veins cannot be safely or effectively treated with thermal energy, regardless of how symptomatic they are or how severe the reflux measures. 2, 3
Recommendation
Non-certification of CPT codes 36475 and 36476 for the left small saphenous vein is appropriate. 1, 2 The patient should continue conservative management with compression therapy for the left leg symptoms, as the vein anatomy does not support interventional treatment with thermal ablation. 4, 2