Spontaneous resolution of delayed onset large subclavian artery pseudoaneurysm.

A 70-year-old woman with a history of end-stage renal disease secondary to anti-neutrophil cytoplasmic autoantibody-associated vasculitis had been receiving hemodialysis for 5 years. The patient underwent attempted right internal jugular vein cannulation for temporary hemodialysis catheter placement. Pulsating mass developed in the neck and angiography revealed a subclavian artery pseudoaneurysm 4 days later. The pseudoaneurysm disappeared spontaneously during the interval between the diagnosis and the planned surgical procedure. Such delayed onset and spontaneous resolution of subclavian artery pseudoaneurysm is uncommon. Close observation may be optimal if delayed onset of pseudoaneurysm occurs after small needle puncture with cessation of antiplatelet/anticoagulant administration.