POLYPOID ARTERIOVENOUS MALFORMATION OF THE URETER

Abstract

Congenital arteriovenous malformations of the genitourinary system are exceedingly rare. The majority are located in the kidney or bladder. Only 1 case of arteriovenous malformation of the ureter has been previously reported.' We describe a case of an unusually long polypoid arteriovenous malformation of the mid ureter. Arteriovenous malformations are exceedingly rare but clinically they may mimic a fibroepithelial polyp. Histological examination of arteriovenous malformations shows multiple large caliber blood vessels with thromboses. In contrast, fibroepithelial polyps are characterized by an edematous submucosa with fibrous collagenous stroma and chronic inflammation.13 CASE REPORT A 29-year-old black woman presented with intermittent gross hematuria and right lower quadrant pain. A brief episode of right flank pain 1 year previously had been attributed to a renal calculus, although no stone was recovered. Physical and laboratory evaluations were remarkable only for microscopic hematuria. Cytological evaluation of the urine showed no malignant cells. Excretory urography (IVF') demonstrated right hydroureteronephrosis to the level of the mid ureter and retrograde pyelography confirmed a 12 cm. filling defect extending from the mid to distal ureter (fig. 1, A). Ureteroscopy using an 8F semirigid ureteroscope showed a long polypoid mass originating in the mid ureter and extending into the intramural ureter. Frozen section biopsy of the mass revealed benign urothelial mucosa with prominent submucosal vessels. The polyp was debulked using a 2F right angle Greenwald electrosurgical probe but complete excision was not done because of inadequate visualization of the base of the bulky mass. The remainder of the lesion was resected endoscopically at a second setting using a Greenwald electrode, and the base of the lesion was fulgurated. An indwelling ureteral stent remained in place for 6 weeks. Followup IVP at 3 and 9 months showed no residual filling defect or obstruction (fig. 1, B). The patient remains asymptomatic with a normal urinalysis 9 months postoperatively. Gross pathological examination demonstrated a contracted 2.8 x 0.5 x 0.5 cm. polypoid tan glistening mass. Histological evaluation revealed numerous large dilated submucosal arterial and venous blood vessels with irregular eccentric thickening of the walls and multiple foci of thrombosis, consistent with a polypoid arteriovenous malformation (fig. 2). The overlying urothelium was unremarkable.