A Rare Vascular Challenge: Brachial Artery Collateral Pseudoaneurysm Managed With Vein Grafting.

Upper extremity pseudoaneurysms are uncommon, and involvement of collateral branches of the brachial artery is particularly rare. A 78-year-old woman without antecedent trauma presented with a new pulsatile mass and progressive dysfunction of the proximal arm. Duplex ultrasonography provided sufficient diagnostic and planning information, demonstrating a pseudoaneurysm arising from a collateral branch of the brachial artery measuring 38 mm × 29 mm × 46 mm, with an estimated neck diameter of 3 mm and neck length of 5 mm, and a thin peripheral mural thrombus. Given lesion size and compressive features, open repair was performed under general anesthesia: sac excision and arterial reconstruction with a reversed basilic vein interposition graft using end-to-end anastomoses. The postoperative course was uneventful, with discharge on postoperative Day 1; at 7-day follow-up, duplex ultrasonography confirmed patency of the reconstructed segment without stenosis, residual sac, arteriovenous fistula, or signs of distal ischemia. This case supports open venous autologous reconstruction as an effective option for large and compressive arterial pseudoaneurysms of brachial collateral branches.