Fulminant Colitis and Toxic Megacolon
Stephen B. Hanauer
Ulcerative colitis is characterized by a diffuse, continuous inflammatory process usually limited to the superficial mucosa of the colon. Fulminant colitis implies progression of mucosal inflammation into deeper (muscular) layers of the colon wall. It generally is associated with severe bloody diarrhea, fever, tachycardia, and abdominal tenderness. Systemic manifestations result from transmural colitis, which may also produce circular muscle paralysis precipitating dilatation. Toxic megacolon refers to acute dilatation of the colon, generally as a complication of ulcerative colitis, but it may occur with any severe inflammatory colitis. Toxic megacolon has been described with idiopathic and infectious colitis, including ulcerative colitis, Crohn’s disease, amebic colitis, pseudomembranous colitis, and other infections [1]. Toxic megacolon has been reported to complicate from 1% to 13% of all ulcerative colitis cases [2] and from 2% to 3% of Crohn’s colitis cases [1]. Although mortality in early series was as high as 25% (reaching 50% if colonic perforation occurred), early recognition and management of toxic megacolon has substantially lowered mortality to below 15% [3] and usually below 2% in experienced centers [4]. Factors associated with increased mortality include age older than 40 years, the presence of colonic perforation, and delay of surgery [3,4]. Colonic perforation, whether free or localized, is the greatest risk factor leading to increased morbidity or death.
Predisposing Factors
The severity of disease activity is the most important predictor of toxic megacolon, which is more common in extensive colitis than in proctitis or proctosigmoiditis [5]. Limited right- or left-sided segmental colitis also has been associated with toxic megacolon. Concomitant Clostridium difficile infection often occurs in hospitalized patients with inflammatory bowel disease and can be associated with refractory disease [6,7]. Similarly, cytomegalovirus (CMV) infections frequently complicate colitis in the setting of immune suppression with corticosteroids or cyclosporine [8,9]. Treatment of CMV with ganciclovir usually is not necessary unless there are systemic manifestations such as fever or associated hepatitis.
Toxic megacolon typically occurs early in the course of ulcerative colitis, usually within the first 5 years of disease, and 25% to 40% of cases present with the initial attack [1]. The onset of toxic megacolon has been linked to patients who have recently undergone diagnostic examinations, such as barium enemas or colonoscopy, suggesting that manipulation of the inflamed bowel or vigorous laxative preparation may exacerbate the process, possibly through electrolyte imbalance (Table 94.1) [3,10].
Certain drug therapies have been implicated in the development of toxic megacolon. Diphenoxylate hydrochloride/atropine sulfate (Lomotil), loperamide, and other inhibitors of colonic motility such as opiates and narcotics may contribute to the development of toxic megacolon by inhibiting colon muscle function in severe transmural disease [11].
Table 94.1 Potential Precipitants of Toxic Megacolon | ||
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Electrolyte and pH disturbances are risk factors for toxic megacolon. Severe potassium depletion, secondary to severe diarrhea or corticosteroid therapy, or both, is known to inhibit colonic motility. Potassium requirements of patients with colitis
may be massive, and restoration of serum potassium alone may not be adequate to replenish body stores [1,11].
may be massive, and restoration of serum potassium alone may not be adequate to replenish body stores [1,11].
Despite early speculations on the role of corticosteroids in inducing toxic megacolon, most experienced clinicians do not accept the implication that corticosteroids or adrenocorticotropic hormone are precipitating factors [1,11,12,13]. Concern remains, however, that corticosteroids may suppress signs of perforation, thereby delaying surgical therapy.
Clinical Features
Toxic megacolon usually occurs on the background of chronic inflammatory bowel disease [1,3]. The presentation typically evolves with progressive diarrhea, bloody stool, and cramping abdominal pain. Occasionally, in patients treated for inflammatory bowel disease over long periods of time, a paradoxic decrease in stool frequency with passage of only bloody discharge or bloody membranes may be an ominous sign (Table 94.2). Thereafter, clinical signs of toxemia, including pyrexia (temperature > 101.5°F), tachycardia, and leukocytosis (total white blood cell count > 10,500 cells per μL), develop as abdominal pain and distention become progressive and bowel sounds diminish or cease. Signs of peritoneal irritation, including rebound tenderness and abdominal guarding, represent transmural inflammation to the serosa, even in the absence of free perforation. Conversely, peritoneal signs may be minimal or absent in elderly patients or those receiving high-dose or prolonged corticosteroid therapy. In such patients, loss of hepatic dullness may be the first clinical indication of colonic perforation. Mental status changes, including confusion, agitation, and apathy, occasionally are noted. Leukocytosis with a left shift generally is present. Anemia, hypokalemia, and hypoalbuminemia are common. The presence of anemia, requirement for transfusion hypoalbuminemia, and malnutrition are poor prognostic factors [14,15].
Plain films of the abdomen usually are sufficient radiographic studies, revealing loss of haustration with segmental or total colonic dilatation. Clinical studies have demonstrated a strong correlation between colonic dilatation and deep ulceration involving the muscle layers [16]. The magnitude of dilatation may not be severe, averaging 8 to 9 cm (normal is < 5 to 6 cm), although colonic diameter may reach 15 cm before rupture. Maximal dilatation can occur in any part of the colon. Accompanying mucosal thumbprinting or pneumatosis cystoides coli reflect severe transmural disease. Free peritoneal air should serve as an immediate indication for surgery [3]. Infrequently, retroperitoneal tracking of air from a colonic perforation may produce subcutaneous emphysema and pneumomediastinum without pneumoperitoneum. In patients with severe colitis, small bowel ileus may herald toxic megacolon and is a bad prognostic sign for medical success. Discrepancies may exist between physical and radiographic findings. Abdominal distention by physical examination can be minimal despite massive colonic dilatation. Conversely, physical findings may dominate the presentation, and peritoneal signs in the absence of free air or dilatation should not be ignored.
Table 94.2 Clinical Features of Toxic Megacolon | |
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A limited proctoscopic or flexible sigmoid examination generally shows extensive ulceration with friable, bleeding mucosa. In rare instances, however, such as with rectal enema therapy or Crohn’s disease, the rectum may be normal [17]. An abdominal radiograph after cautious proctoscopic examination can assist in determining the extent and severity of colitis. Computed tomography scans can demonstrate thinning of the colonic wall or evidence of perforation or abscess [1]. More extensive endoscopic examinations, although controversial, generally are contraindicated. If performed, the presence of severe colitis (deep penetrating ulcers) in conjunction with clinical features of severe disease is a poor prognostic sign [16]. Similarly, the presence of extensive and deep ulcerations is a poor prognostic marker in Crohn’s disease [17].
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