Amoebic perforation of the intestine in children

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.

Perforation of the colon in unsuspected amebic colitis: report of two cases

Two cases of amebic colitis that resulted in perforation of the colon, an ominous complication, are presented. The first was diagnosed preoperatively as acute ulcerative colitis with toxic megacolon, and the second as peritonitis complicating acute cholecystitis. In both instances the correct diagnosis was made after operation. The first patient recovered after colectomy and antiamebic therapy, but the second patient died in the early postoperative period, in septic shock. Amebic colitis occurs infrequently in the United States, and the diagnosis is rarely considered. In most cases an initial diagnosis of ulcerative or granulomatous colitis is made and the true diagnosis is recognized only after operation for colonic perforation or hepatic abscess. It is suggested that amebic colitis should be considered more frequently in cases of patients who have diarrhea. Stool examination for ova and parasites is often negative in amebic colitis. The IHA is usually positive in emebiasis, and should be performed early in casesof patients who have bloody diarrhea or other clinical symptons when amebiasis is suspected. Rectal biopsy is also a useful diagnostic approach, but failed to reveal amebae in one of our cases. Finally, it is suggested that operation be performed urgently when fulminating amebic colitis is not reversed by antiamebic therapy, when peritonitis occurs even with antiamebic treatment in progess, and for colonic perforation or toxic megacolon even when antiamebic therapy has not been indicated.