Unusual differential diagnoses for unilateral lower limb swelling: a case of arteriovenous malformation and deep vein thrombosis

Background: Unilateral lower limb swelling presents a broad differential diagnosis, often attributed to deep vein thrombosis (DVT), lymphedema, or cellulitis. However, arteriovenous malformation (AVM) remains a rare but critical consideration. Case Presentation: An 89-year-old Middle Eastern man with a known case of AVM of the left thigh presented with worsening swelling and patchy skin discoloration in the affected limb. The patient also had a history of DVT and was bed-bound due to an old stroke for several years. Initial Doppler studies ruled out recurrent DVT. Further imaging with computed tomography angiography identified an arteriovenous fistula between the common femoral artery and vein, likely secondary to post-thrombotic recanalization. In addition to embolization and stenting, vascular surgery introduced an external pneumatic compression device to reduce venous congestion and manage limb swelling. This approach was adopted to provide symptomatic relief while minimizing the risks associated with invasive interventions. Conclusion: This case highlighted the importance of considering AVM in patients with unexplained limb swelling post-DVT. Advanced imaging techniques play a crucial role in diagnosis, and a multidisciplinary approach is essential for optimal management.