Late Arteriovenous Fistula After Deep Vein Thrombosis in a Young Patient: A Case Report

Background and Clinical Significance: Acquired arteriovenous fistula (AVF) following deep vein thrombosis (DVT) is an uncommon condition, typically reported in association with persistent venous obstruction. Case Presentation: We report the case of an 18-year-old male with pulmonary embolism (PE) and extensive left iliofemoral–popliteal DVT treated with anticoagulation and compression therapy. Follow-up duplex ultrasound demonstrated progressive venous recanalization, with complete restoration of popliteal vein patency and persistent external iliac vein occlusion. During routine surveillance, in the absence of post-thrombotic symptoms, a popliteal AVF was incidentally detected. This anatomical localization is exceptionally rare, and the delayed appearance of the lesion after documented venous patency makes an early recanalization-related mechanism less likely. Although the absence of overt post-thrombotic syndrome limits definitive conclusions, a delayed hemodynamic alteration secondary to persistent proximal venous outflow obstruction was hypothesized as a possible contributing factor. Given the asymptomatic presentation and recent detection, conservative management comprising anticoagulation, elastic compression, venoactive therapy, and close ultrasound follow-up was adopted. Conclusions: This case highlights that post-thrombotic AVFs may manifest as late incidental findings and supports a tailored management approach based on clinical and hemodynamic features.