NMS. Casos Clínicos

278 Part II ♦ Specific Disorders coagulated or, in the case of pedunculated polyps, ensnared. “Tattooing” of the bleeding site allows precise localization if operative intervention is necessary (i.e., in the case of a colonic mass or polyp). Colonoscopy indicates multiple diverticula in the left colon and no vascular ectasia. There is no active bleeding. The patient has a stable hematocrit and is tolerating a regular diet. Q: What is the next step? A: Discharge with outpatient follow-up is appropriate. Most physicians would place the patient on iron and a high-fiber diet, which may lessen the chance of the development of additional diverticula. Q: Why are diverticula associated with bleeding? A: Colonic diverticular bleeds result from an underlying vasa recta artery penetrating the bowel wall through the neck or the apex of a diverticulum and become eroded. Although most diverticula in the colon are left sided, right-sided colonic diverticula are more apt to bleed (Fig. 8-37). Q: What are vascular ectasias? A: Vascular ectasias, or arteriovenous malformations , are thought to arise from the degen- eration of intestinal submucosal veins and overlying mucosal capillaries (Fig. 8-38). As the disease progresses, communications between submucosal arteries and veins form. When the mucosa erodes or becomes disrupted for some reason, massive lower GI bleeding may result.

Antimesenteric taenia Antimesenteric intertaenial area

Antimesenteric taenia

Medial wall Figure 8-37: The blood supply of the colonic wall and its association with diverticula within the wall of the colon, which explains why diverticulosis has a tendency to bleed. (From McKenney MG, Mangonon PC, Moylan JA, eds. Understanding Surgical Disease: The Miami Manual of Surgery . Philadelphia: Lippincott-Raven; 1998:154.) SAMPLE Medial wall Mesenteric taenia Diverticula “false”