The amoebic ulcerations rarely extend above the ileo-caecal valve but may involve the entire large intestine. Rogers and Lafleur found the lesions most often in the caecum and ascending colon, often limited to this area.
The appendix was involved in 7% of the Manila autopsies. Often mild cases may only show lesions in the caecum. When there is a tendency to perforation the omentum will often be drawn over to the location of the threatened perforation. There is often thickening of the intestine in one place with cicatricial contraction of the lumen and thinning in another, so that there is an appearance of great irregularity.
Symptomatology
The great majority of cases of amoebic dysentery run a chronic course with periods of improvement alternating with recurrences of pains and dysenteric stools. From Walker’s experiments the period of incubation would appear to be from one to three months. The onset in such cases is very insidious and the patient may complain more of diarrhoeal than dysenteric manifestations. Such patients often give a history of passing three or four pultaceous stools daily and complain of tenderness in the region of the caecum or along the course of the large intestine. One may determine some thickening of the colon in a thin subject.
Fever is absent and there are very few of the toxic manifestations which often accompany bacillary dysentery, such as headache, nausea and a mildly delirious state. There is progressive loss of weight and strength with the development of neurasthenic symptoms. The skin becomes dry and earthy and we have the picture of a more or less marked secondary anaemia. It is in these cases that we should be on the lookout for grayish green or grayish brown mucoid masses which can usually be found during an exacerbation. Sloughs of the gelatinous-like necrosis in the submucosa usually contain amoebae.
The X-ray has been utilized to give location of amoebic ulcerations. Bismuth is used for several days prior to taking the photograph and fills the sites of ulceration.
Such cases usually show a moderate leucocytosis in which the percentage of large mononuclears is increased and a very important point is that with tenderness about the caecum, plus a leucocytosis, one may diagnose appendicitis and operate on a normal appendix. Autopsy records however have shown that the appendix is not infrequently invaded by amoebae but in some of these cases, other than finding amoebae in the lumen of the appendix, I have been unable to note any change. Cases of amoebiasis confined to caecum and ascending colon may only show symptoms of slight anaemia.
Besides the more common insidious chronic type we may have amoebic dysentery setting in quite acutely with severe griping and frequent scanty grayish green to reddish brown mucoid stools.
Such cases may show anorexia and nausea with some fever but there is not present the manifestations of toxemia one associates with a severe case of bacillary dysentery in the tropics.
Very confusing cases are those in which a bacillary dysentery sets in upon an amoebic one and this possibility should always be thought of when a severe bacillary dysentery does not respond to serum therapy or an amoebic one to emetine.