SURGICAL PROBLEMS IN AMOEBIASIS E. Q. ARCHAMPONG F.R.C.S., F.R.C.S.Ed. C. G. CLARK M.D., Ch.M., F.R.C.S., F.R.C.S.Ed. Department of Surgery, University College Hospital Medical School INFESTATION WITH PATHOGENIC amoebae is geographically the most widely distributed of the protozoal diseases. The general surgeon is liable to be faced with complications arising from amoebiasis wherever he works. With increased intercontinental travel the condition is now more frequently encountered in countries with a high standard of living, where it may be confused with other diseases of the colon. In endemic areas the disease is often diagnosed too readily, and the manifestations of the disease are liable to differ, depending perhaps on the nutritional state of the patient. Differences occur in clinical presentation, and the course of the disease varies in different communities. It is not surprising therefore that there is controversy regarding management. An attempt has been made in this paper to provide some guidance for the surgeon faced with the complications of amoebiasis. Pathogenesis Amoebiasis is an infection due to Entamoeba histolytica, which is ingested with contaminated food. The lesions produced by E. histolytica in the colonic mucosa involve principally the caecum, ascending colon, and rectosigmoid, the latter fortunately allowing access to biopsy material for diagnosis. Craig and Faust' found that in symptomatic patients the lesions were generalized throughout the colon in 60% of cases and localized in the remainder. The initial lesion seen on sigmoidoscopy is a characteristic punched-out ulcer, or undermined ulcers with yellowish-grey exudate in the base. Un- fortunately, in the rectum there is often associated oedema and attendant inflammation which may obscure the typical ulcers, thus making it impossible to differentiate amoebic from other forms of dysentry on proctoscopy. At first there is only a mild cellular reaction to the amoebae, and in the early stages the serosa and muscular wall of the colon show little change. Later, because of secondary invasion, the intes- tinal wall becomes a little thickened by oedema, though invasion of lymphatics by amoebae is seldom demonstrated and regional lymph- From a Postgraduate Lecture (Ann. Roy. Coll. Surg. Engl. 1973, vol. 52) 36 SURGICAL PROBLEMS IN AMOEBIASIS adenopathy is rare. This results in a tendency to underestimate the severity of the lesion if for any reason laparotomy is performed. Amoebic lesions generally heal without extensive cicatrization, though the regenerated mucous membranes may be thin and atrophic, with deficient glands and mucus production. Occasionally pseudopolypi occur, and more rarely an amoebic granuloma (amoeboma) is found in the region of the caecum or rectosigmoid. These are uncommon lesions in actively treated patients, but when they occur early revision of the diag- nosis is imperative. The mild cellular reaction to amoebae may permit ready access of the parasite to the vascular tree; however, the low incidence of extra- intestinal foci (2-5% ) suggests that most amoebae perish before estab- lishing metastatic foci. Amoebic abscess may occur in the lung, pleura, or pericardium, and occasionally in the brain, but the commonest ectopic site is the liver. Many amoebae undoubtedly invade the portal vein and are transported to the liver, but Craig and Faust' have emphasized that it is the liver whose resistance is decreased by other factors such as alcoholism which becomes affected. Most amoebic liver abscesses are solitary, sterile, and situated in the right lobe of the liver. They result from misdiagnosis and delayed or ineffective treatment. Symptoms If the definition of amoebiasis as an infection with the pathogenic amoeba E. histolytica be accepted, then the disease may be regarded as occurring in invasive and non-invasive forms. The latter is symptomless, the organism living commensally in the colon and being discovered only on routine stool examination. Although amoebiasis is regarded primarily as a tropical infection, 5-10% of subjects in temperate climates harbour either amoebae or amoebic cysts3. If the stools are examined because of irregular bowel action the amoebic trophozoite may be found, but unless it contains engulfed red cells it may be entirely blameless. The unfortunate tendency to attribute an aetiological role to E. histolytica in all situations has contributed to a state of amoebophobia which is increasingly encountered in visitors to tropical and subtropical countries. The symptomatology of invasive amoebiasis is not well understood, particularly in the temperate regions of the world, where perhaps from a higher standard of living the manifestations are often mild. An aver- age attack may manifest itself as no more than a windy looseness of stools with 2-3 postprandial defaecations daily, preceded by colic and aching in the rectum4. Passage of macroscopic blood may or may not be evident. The finding of E. histolytica in the stools and permanent relief of symptoms with specific treatment are confirmatory evidence of the disease. Untreated, symptoms may wax and wane or progress to the more serious disease. 37 E. Q. ARCHAMPONG AND C. G. CLARK Because of the poorer standard of living and health the disease takes a more severe form in developing countries, and occasionally this variety may be seen in temperate latitudes. The presentation may simu- late the clinical picture of shigellosis, with high fever and acute fulminating dysentery characterized by diarrhoea with blood, pus, and mucus. This later deteriorates into passage of copious exudate replacing the liquid stools, leading to profound fluid and electrolyte disturbance. Abdominal tenderness is frequent and later distension supervenes. Diagnosis The diagnosis is confirmed by the identification of the parasite in fresh stool specimens, ulcer scrapings, and rectal biopsy specimens. In nearly all symptomatic patients haemotophagous trophozoites of E. histolytica are seen; cysts occur only in mild cases and then identification is aided by flotation methods5. Characteristic punched-out or undermined ulcers, the floor covered with yellowish-grey exudate, may be seen at sigmoidoscopy in half the patients with active colitis6, but the appearances are seldom diagnostic since it is not always possible to differentiate amoebiasis from other causes of dysentery on the basis of mucosal changes. The procedure, however, affords the means for biopsy and obtaining fresh stool speci- mens; it is safe and requires no preparation besides bowel evacuation shortly before examination. The characteristic sigmoidoscopic appear- ance is one of inflamed, oedematous mucosa, ulcers being often but not always identifiable. Although recent advances have made possible the culture of E. his- tolytica7, 8 this technique is of limited value in the laboratory investiga- tion of the disease, yielding a lower incidence of positive results than microscopical examination7. Amoebiasis confined to the colon produces little change in the peri- pheral blood, and even in the presence of secondary infection a white cell count of 10,000/mm3 is seldom exceeded9' 10. Anaemia is not a feature of the uncomplicated disease and patients with a raised erythro- cyte sedimentation rate are often found to harbour hepatic abscesses. Barium enema examination is of little value except perhaps for the location of ulcers high in the sigmoid colon, and in severe cases may be dangerous. Ulceration is demonstrable in about 25-35% of dysenteric patients, usually associated with irritability of the colon'1. Serological tests may prove useful in specific circumstances. In par- ticular the gel diffusion precipitin test of Maddison12 has given reliable results. Its limitation is its inability to differentiate recent from past in- fection with E. histolytica It is in the investigation of complications of invasive amoebiasis that the gel diffusion test is most useful. In non- 38 SURGICAL PROBLEMS IN AMOEBIASIS endemic areas a negative reaction to the test may virtually exclude amoebiasis; in the endemic areas, however, where the problem of diag- nosis of complicated lesions is most difficult, positive reactions have limited value. Efforts to develop a more discriminative technique have so far been unavailing. The differential diagnosis of amoebic colitis lies mainly between the other infective causes of colitis-bacillary dysentery, salmonellosis, and balantidiasis. Granulomatous conditions such as ulcerative colitis, Crohn's disease, schistosomiasis, and neoplasms of the large bowel need careful consideration. The diagnosis is conditional on the finding of amoebae in all cases, but due regard needs to be given to the fact that amoebiasis may coexist with other bowel lesions. Treatment of amoebic colitis The large number of drugs currently available for the treatment of amoebiasis makes caution necessary in the choice of the most appro- priate regimen. The ideal drug would be one capable of destroying E. histolytica in both tissues and bowel lumen. From the studies of Powell13 and Haddock14 it is evident that metronidazole, given in doses of 800 mg 3 times daily for 5 days, closely approaches this ideal. The drug has a high margin of safety, only occasionally producing nausea and vomiting. Its clinical use is limited by the lack of a parenteral preparation. In the event of persistent or recurrent symptoms a second course of the drug may be administered or one of the combinations of older drugs described by Wilmot5: 1. (a) Tetracycline 250 mg