Complications

Complications of ulcerative colitis include massive hemorrhage, toxic megacolon, perforation of the bowel, strictures and colon cancer. Massive hemorrhage can occur with severe ulcerative colitis and is managed with blood transfusions and treatment of the underlying ulcerative colitis; urgent colectomy may be required. One consensus group suggested that an individual with ulcerative colitis who requires more than 6-8 units of blood in the first 48h and is still actively bleeding should undergo a colectomy.120 Colonic perforation is the most dangerous complication of ulcerative colitis. It can occur in the setting of severe ulcerative colitis with or without toxic colonic dilatation,121-123 and requires urgent colectomy.

Toxic megacolon is a potentially life-threatening complication of ulcerative colitis and is characterized by total or segmental non-obstructive colonic dilatation of at least 6 cm in adults associated with systemic toxicity.122,124,125 Previous reports suggest a lifetime risk of toxic megacolon complicating IBD of 1-5%, but this has decreased more recently, probably secondary to earlier recognition and improved management of severe colitis.122,126 The pathogenesis of toxic megacolon is most likely to be multifactorial.122 In contrast to typical ulcerative colitis, in which the inflammatory changes are limited to the mucosa, in toxic megacolon, the severe inflammation extends into the deeper layers of the colonic wall.121 It is thought that the spread of the inflammatory process to the smooth-muscle layer may lead to the paralysis of the colonic smooth muscle and subsequent dilatation of the colon.122 Nitric oxide, an inhibitor of smooth muscle tone, may be involved in the pathogenesis of this condition.127

Several triggering factors have been reported to precede the development of toxic megacolon.121,122 Medications that can impair colonic motility should be avoided. They have been implicated as precipitating factors, including narcotic agents for pain or antidiarrheal effects, anticholinergic agents, drugs that decrease motility, or antidepressants with significant anticholinergic effects.121,128,129 A barium enema or colonoscopy may cause distension that can further impair the colonic wall blood supply and may increase the mucosal uptake of bacterial products.122 Barium enema examinations have been reported in proximity to the development of toxic megacolon.83,129 The early discontinuation or rapid tapering of steroids or 5-aminosalicylic acid (5-ASA) may contribute to the development of toxic mega-colon.121,122 Electrolyte abnormalities, such as hypokalemia, have been observed in the setting of toxic megacolon, although it is not clear whether this finding is a causative factor or secondary to the illness itself.121 Along with colonic dilatation, patients with toxic megacolon present with systemic findings, including fever, tachycardia, leukocytosis and anemia.124 A decrease in the number of stools may herald the onset of toxic

Colonic Dilatation

Figure 25.4 Toxic megacolon in a teenager with fulminant ulcerative colitis. There is a massively dilated loop of transverse colon in the upper quadrants, with a paucity of bowel gas in the remainder of the abdomen. This patient developed the megacolon despite corticosteroid therapy, and subsequently underwent emergent surgery for a colonic perforation. (Courtesy of Carlo Buonomo, MD, Department of Radiology, Children's Hospital, Boston).

megacolon. With progressive disease, these individuals can develop dehydration, mental status changes, electrolyte disturbances, hypotension and increasing abdominal distension and tenderness, with or without signs of peritonitis.122,124

Abdominal X-ray reveals colonic dilatation, most frequently involving the transverse colon, sometimes accompanied by inflammatory changes including an absent or markedly edematous haus-tral pattern130 (Figure 25.4). In two series of adults with toxic megacolon, the diameter of the colon varied, with a range of 5.8-16cm.125,129 Because the transverse colon is the most anterior portion of the colon, air will tend to accumulate in this segment of the colon when the patient is in the supine position; however, with repositioning of the patient, the colonic air will redistribute, filling other segments of the bowel.131

The management of toxic megacolon is detailed in multiple reviews elsewhere.121,122 If toxic megacolon is present, surgical consultation is essential, and the patient will probably require a colectomy. Some authors have utilized medical management of this condition; however, this requires very close monitoring to avoid complications.132 Early surgical intervention is indicated in the setting of failed medical therapy with progressive colonic dilatation, worsening systemic toxicity, perforation or uncontrolled hemorrhage.122

Both benign and malignant colonic strictures can develop in longstanding ulcerative colitis.75,133,134 Benign strictures present most commonly in the rectum and the sigmoid, are due to smooth-muscle hypertrophy and are thought to be potentially reversible.133 Colonic strictures should be evaluated for possible malignancy, but the majority of strictures in ulcerative colitis are benign.75,133,134 There is an increased risk of dysplasia and colon cancer in patients with longstanding ulcerative colitis, which is addressed later in this chapter (see Prognosis and follow-up, p.407).

Figure 25.4 Toxic megacolon in a teenager with fulminant ulcerative colitis. There is a massively dilated loop of transverse colon in the upper quadrants, with a paucity of bowel gas in the remainder of the abdomen. This patient developed the megacolon despite corticosteroid therapy, and subsequently underwent emergent surgery for a colonic perforation. (Courtesy of Carlo Buonomo, MD, Department of Radiology, Children's Hospital, Boston).

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