A 52-year-old man presents with dilated, tortuous veins in the lower limb. On examination, he has incompetence of the saphenofemoral junction. What is the most common cause of primary varicose veins?

Explanation

## Aetiology of Primary Varicose Veins **Key Point:** Primary varicose veins result from intrinsic weakness of the vein wall and/or valve incompetence, not from obstruction or thrombosis of deep veins. ### Pathophysiology Congenital weakness of the vein wall (deficiency in elastic fibres and smooth muscle) combined with valve incompetence is the most common cause of primary varicose veins. This leads to progressive venous dilation and reflux, particularly at the saphenofemoral and saphenopopliteal junctions. ### Classification of Varicose Veins | Type | Cause | Frequency | |------|-------|----------| | **Primary** | Congenital wall weakness + valve incompetence | 90% | | **Secondary** | DVT, venous obstruction, AV fistula | 10% | ### Why Primary Varicose Veins Occur 1. **Congenital wall weakness** — deficiency of elastic fibres and smooth muscle in the vein wall 2. **Progressive valve incompetence** — stretching of the vein leads to valve leaflet separation and reflux 3. **Increased venous pressure** — reflux worsens with gravity and prolonged standing 4. **Vicious cycle** — progressive dilation → more valve incompetence → more reflux **High-Yield:** The saphenofemoral junction is the site of incompetence in ~90% of cases with primary varicose veins of the long saphenous vein. **Clinical Pearl:** Absence of valves is rare and does not explain the majority of cases; most patients have structurally present but incompetent valves.