Which of the following is the most common cause of primary varicose veins?

Explanation

## Etiology of Primary Varicose Veins **Key Point:** Primary varicose veins (90% of cases) result from intrinsic weakness of the venous wall combined with valve incompetence, not from obstruction or thrombosis. ### Pathophysiology The underlying defect in primary varicose veins involves: 1. Congenital or acquired weakness of the venous wall (smooth muscle and elastic fibers) 2. Secondary valve incompetence due to venous dilation 3. Loss of normal venous tone and elasticity 4. Genetic predisposition (positive family history in 60% of cases) ### Classification of Varicose Veins | Type | Mechanism | Frequency | |------|-----------|----------| | **Primary** | Venous wall weakness + valve incompetence | 90% | | **Secondary** | Post-thrombotic, obstruction, AV fistula | 10% | **High-Yield:** Primary varicose veins are NOT caused by previous DVT or obstruction—these cause *secondary* varicose veins. The defect is in the vein wall itself, not in the venous system's drainage capacity. ### Why Wall Weakness Matters - Reduced collagen and elastin in the medial layer - Loss of smooth muscle tone - Progressive dilation → valve leaflets no longer coapt → reflux - Reflux → further dilation → vicious cycle **Clinical Pearl:** Patients with primary varicose veins have normal deep venous function; the problem is isolated to the superficial system.