A Congenital High Flow Arteriovenous Malformation of the Bladder Presenting With Polypoid Cystitis and Ureteral Obstruction.

A 21-year-old male with a history of Down's syndrome presented with hematuria and right flank pain. Computed Tomography (CT) of the abdomen/pelvis revealed right hydronephrosis and a right-sided pelvic vascular abnormality. Angiography revealed an arteriovenous malformation (AVM) fed by the right superior and inferior vesical arteries and nephrostogram showed a long segment of obstructed distal right ureter. Cystoscopy revealed erythema and edema of the right hemi-bladder and biopsy diagnosed polypoid cystitis. Treatment was performed by transarterial embolization with ethylene vinyl alcohol copolymer. Follow up cystoscopy and retrograde pyelography at 3 months post-procedure showed resolution of all visible pathology.