The Wells score for DVT is a validated clinical prediction rule that stratifies patients into probability categories to guide diagnostic workup. The score assigns points based on clinical features: active cancer (+1), paralysis or recent cast immobilization of lower extremity (+1), bedridden >3 days or major surgery within 12 weeks (+1), localized tenderness along deep venous distribution (+1), entire leg swollen (+1), unilateral calf swelling >3 cm compared to asymptomatic side (+1), unilateral pitting edema (+1), collateral superficial veins (+1), previously documented DVT (+1), and alternative diagnosis at least as likely (-2). A score of ≥2 indicates DVT is likely, and <2 indicates DVT is unlikely. For unlikely DVT, a negative high-sensitivity D-dimer effectively excludes the diagnosis without imaging. For likely DVT, compression ultrasonography (CUS) is the first-line imaging modality, with sensitivity >95% for proximal DVT. If initial CUS is negative but clinical suspicion persists, serial CUS at 5-7 days is recommended to detect propagating calf DVT. The age-adjusted D-dimer cutoff (age × 10 mcg/L for patients >50 years) improves specificity without significantly reducing sensitivity, reducing unnecessary imaging by 30%...