Toxic dilatation complicating fulminant amoebic colitis

Toxic megacolon

Toxic megacolon represents a dreaded complication of mainly inflammatory or infectious conditions of the colon. It is most commonly associated with inflammatory bowel disease (IBD), i.e., ulcerative colitis or ileocolonic Crohn's disease. Lately, the epidemiology has shifted toward infectious causes, specifically due to an increase of Clostridium difficile-associated colitis possibly due to the extensive (ab)use of broad-spectrum antibiotics. Other important infectious etiologies include Salmonella, Shigella, Campylobacter, Cytomegalovirus (CMV), rotavirus, Aspergillus, and Entameba. Less frequently, toxic megacolon has been attributed to ischemic colitis, collagenous colitis, or obstructive colorectal cancer. Toxic colonic dilatation may also occur in hemolytic-uremic syndrome (HUS) caused by enterohemorrhagic or enteroaggregative Escherichia coli O157 (EHEC, EAEC, or EAHEC). The pathophysiological mechanisms leading to toxic colonic dilatation are incompletely understood. The main characteristics of toxic megacolon are signs of systemic toxicity and severe colonic distension. Diagnosis is made by clinical evaluation for systemic toxicity and imaging studies depicting colonic dilatation. Plain abdominal imaging is still the most established radiological instrument. However, computed tomography scanning and transabdominal intestinal ultrasound are promising alternatives that add additional information. Management of toxic megacolon is an interdisciplinary task that requires close interaction of gastroenterologists and surgeons from the very beginning. The optimal timing of surgery for toxic megacolon can be challenging. Here we review the latest data on the pathogenesis, clinical presentation, laboratory, and imaging modalities and provide algorithms for an evidence-based diagnostic and therapeutic approach.

Toxic megacolon: role of CT in evaluation and detection of complications

The purpose of this study is to determine the role of CT in the evaluation and in detecting complications in patients with toxic megacolon. A retrospective analysis of CT findings of 18 consecutive patients with toxic megacolon was performed. Underlying etiology included 12 patients with pseudomembranous colitis (PC), four patients with ulcerative colitis and two patients with cytomegalovirus colitis. Eleven patients were HIV+. CT features, correlation with severity of disease and development of complications were analyzed. Colonic dilatation with intraluminal air and/or fluid with a distorted colonic contour or an ahaustral pattern was seen in all patients. In four patients (22%), CT depicted complications-two colonic perforations and two septic thrombosis of the portal system. Six patients died (33%), three of whom had the above complications. The presence and degree of submucosal edema (accordion sign, target sign), wall thickening, degree of dilatation, nodular contour and ascites did not correlate with clinical outcome. Two thirds of patients with toxic megacolon had PC as the underlying etiology. CT was helpful in depicting diffuse colitis, and it was instrumental in detecting life-threatening abdominal complications, contributing to the management of these patients. CT abnormalities cannot be used to predict the clinical outcome unless complications develop.

Clinical evaluation and management of acute severe colitis

This review concentrates on the clinical evaluation, imaging, therapy, and prognostic factors in acute severe colitis of idiopathic as well as infectious origin. Older concepts as well as more recent are critically scrutinized.

Gender distribution in asymptomatic and invasive amebiasis

OBJECTIVE

The majority of individuals infected by the protozoan parasite Entamoeba histolytica experience subclinical infections. However, a small proportion of parasitized individuals develop severe invasive disease such as amebic dysentery or amebic liver abscess. Invasive amebiasis affects predominantly men; the usual explanation for this has been that men have a higher rate of asymptomatic infections and therefore experience a higher rate of invasive disease. To date, there is no convincing evidence of an increased rate of asymptomatic infection of men as compared with women. The purpose of this study was to evaluate the evidence supporting the hypothesis that men have higher rates of asymptomatic infection and thus an increased frequency of invasive amebiasis.

METHODS

We reviewed published reports of invasive amebiasis and population-based parasitological studies from 1929-1997 to compare the gender ratio of asymptomatic and symptomatic E. histolytica infection. Infections with E. histolytica were differentiated from the nonpathogenic E. dispar whenever possible.

RESULTS

The reports of invasive amebiasis (dysentery, liver abscess, colonic perforation, peritonitis, appendicitis, and ameboma) showed a higher proportion of men than women (ratio, male:female = 3.2:1, p < 0.05). This contrasts with the epidemiological surveys, where the rate of asymptomatic infection with E. histolytica was the same (1:1) for both genders (p > 0.05).

CONCLUSIONS

Asymptomatic E. histolytica infection is equally distributed between the genders. The high proportion of men with invasive amebiasis may be due to a male-related susceptibility to invasive disease.

Obstructive enterocolitis: a clinico-pathological discussion

Obstructive colitis is a condition that is not widely appreciated by pathologists. It is defined as an ulcero-inflammatory lesion(s) proximal to a colonic obstruction from which it is separated by a variable length of normal mucosa. Five cases are described which illustrate the clinico-pathological spectrum of the condition. All presented surgically as acute intestinal obstruction, secondary to adenocarcinoma in four cases and a diverticular stricture in one case. Pathologically, the severity of colitis ranged from a single discrete ulcer to an extensive area of fulminant colitis indistinguishable from colitis indeterminate. Furthermore, two cases represented 'obstructive enteritis', a variant of obstructive disease not previously reported. Microscopically, all cases were characterized by distinctive areas of localized ulceration and active inflammation, the features of which were quite unlike those of Crohn's disease or ischaemia, separated by islands of normal mucosa. The role of mural hypoperfusion and secondary localized ischaemia in the pathogenesis of this disorder is discussed. It is suggested that colitis indeterminate represents the final common pathological pathway of the intestine to a wide range of initial insults, be they obstructive or inflammatory.

Toxic megacolon

Toxic megacolon, its incidence, differential diagnosis, and presenting signs and symptoms are reviewed in this article. The typical histologic and radiographic features are described with a review of the potential triggering factors. An outline of requirements for adequate monitoring of the patient with toxic megacolon is provided. The general management and specific medical management are discussed in detail, and the medical outcome with both medical and surgical intervention is reviewed.

Fulminant amebic colitis

Amebiasis is the acute and chronic disease produced by Entamoeba histolytica, an entity which occurs in endemic fashion in many of the tropical and subtropical areas of the world, capable of affecting diverse organs of the body, especially the colon. Amebiasis has different clinical forms of presentation, varying from the asymptomatic carrier state to severe, although not frequent, fulminant or necrotizing colitis, characteristically associated with high morbidity and mortality. We hereby report a series of 50 adult patients with fulminating amebic colitis managed at our institution between January, 1971 and July, 1989, with a global mortality of 60%. Early diagnosis, treatment with effective antiamebic agents--specifically metronidazole--and opportune aggressive surgical intervention have resulted in better survival rates. We had no survivors prior to 1970; our current survival rate is still a dismal 40%, indicating the very severe nature of the disease.

Colectomy for necrotizing amebic pancolitis in early childhood with survival

A case of necrotizing amebic pancolitis in a 6-year-old boy with asplenia, partial situs inversus, and cyanotic congenital heart disease is reported and the literature is reviewed briefly. Our patient was managed successfully by prompt colectomy, ileostomy, a Stamm gastrostomy, and extensive drainage of the peritoneal cavity with administration of metronidazole postoperatively and prolonged jugular vein Broviac catheter hyperalimentation. This child may be the first survivor of total colonic amebic necrosis in childhood. Necrotizing amebic colitis appears to be more hazardous in infancy and childhood than in adult years. Malnutrition and additional illnesses and malformations may produce greater immunocompromise in the very young, placing them at greater risk for the ultimate of amebic intestinal complications, total colonic necrosis and disintegration.

Necrotizing amebic colitis: a frequently fatal complication

Acute necrotizing amebic colitis is an uncommon but life threatening development with a high mortality rate, even when properly diagnosed and treated. We report six cases of acute necrotizing amebic colitis, none of which were diagnosed preoperatively. At operation, five of the six patients had friable, necrotic, and gangrenous colon. A right hemicolectomy with ileostomy was performed in two patients and a subtotal colectomy with ileostomy was performed in four patients. Five of the six patients died within 4 weeks of operation. The sole survivor was the patient who had received metronidazole preoperatively. Only after histologic examination of the surgical specimen was the diagnosis made in all cases. If the diagnosis can be made preoperatively and antiamebic therapy instituted, surgical resection may decrease the high mortality rate of this disease.

Histological evolution of caecal lesions in experimental amoebiasis

Histopathological studies in guinea-pigs infected intracaecally with Entamoeba histolytica were carried out longitudinally on days 3, 7, 11, 15, 20 and 35 after infection. Three characteristic modes of development of caecal lesions were observed. These in order of their prevalence were the classical inflammatory cellular infiltration, lymphoid hypertrophy and necrotizing colitis. Occasional amoeboma formation was observed in progesterone-treated animals. This is the first time that histological lesions which mimic the human intestinal amoebiasis have been described in the experimental animal.

Toxic megacolon secondary to pseudomembranous colitis

Toxic megacolon has rarely been reported in the course of antibiotic-induced pseudomembranous colitis. We have been able to collect 20 cases from the literature and add one new case. The mortality in the collected series was 33 per cent. The critical factor in improving survival is early recognition of the pseudomembranous colitis. Most patients can be managed medically by removal of the offending antibiotic, bowel rest, vancomycin, and steroids. If toxic megacolon develops in the face of appropriate medical management, an aggressive surgical approach is indicated, as with ulcerative colitis. Subtotal colectomy appears to be the procedure of choice.