Endoscopic resection of asymptomatic, colonic, polypoid arteriovenous malformations: Two case reports and a literature review

Abstract

A colonic arteriovenous malformation (AVM) is a significant vascular lesion of the gastrointestinal tract and a common cause of lower gastrointestinal bleeding. AVMs are usually identified endoscopically as bright red, flat lesions. AVMs with a polypoid appearance are extremely rare in the large intestine. We present two cases of colonic polypoid AVM, which were detected incidentally during screening colonoscopy. Both the patients had no history of gastrointestinal bleeding such as melena or hematochezia. Colonoscopy revealed pedunculated polyps overlaid by hyperemic mucosa in the ascending colon and proximal sigmoid colon. Microscopic examination showed aberrant vessels with thickened, hypertrophic walls in the mucosa and the submucosa, and arteries were directly connected to veins without capillary beds. These features were compatible with a diagnosis of AVM with a polypoid appearance. No immediate or delayed bleeding was noted after polypectomy.

Figure 1

Endoscopic views of the polyps. (a) Colonoscopy revealed a 3.0-cm-long pedunculated polyp in the ascending colon (Case 1).

Figure 2

Histological findings of resected specimens. (a) Case 1. Numerous dilated and irregularly thickened blood vessels are observed in the mucosa and submucosa (hematoxylin and eosin staining, magnification ×10). (b) Case 1. At higher magnification, some vessels have thin collagenous walls of veins (short arrows), whereas others have muscular and elastic laminae of arteries (long arrows). There is no intervening capillary bed (hematoxylin and eosin staining, magnification ×200). (c) Case 2. Tangles of abnormal vessels of various diameters are evident (hematoxylin and eosin staining, magnification ×10)