Intestinal amoebiasis, clinical features

We can differentiate 4 different situations in intestinal amoebiasis :

• asymptomatic carriers

• amoebic colitis

• fulminant colitis

• amoeboma

Asymptomatic carriers

Trophozoites can sometimes remain in the intestinal lumen for years without causing any damage: the patient is then an asymptomatic carrier. The majority (90%) of patients fall into this group. Asymptomatic carriers have by definition no symptoms of amoebiasis. These persons can be detected by faeces analyses. This may show cysts of non-pathogenic E. dispar or of potentially pathogenic E. histolytica, which for unknown reasons is not invasive. Differentiation with cysts of Entamoeba coli (which are larger and have 8 nuclei), and others, is important. Entamoeba coli is not pathogenic.

Amoebic colitis

The incubation period of amoebic colitis varies greatly. When Entamoeba histolytica penetrates the intestinal mucosa (becomes invasive) it produces ulcerations of the colonic mucosa [Gr. histo-lytica  breaking down tissues]. The ulcerations are sharply defined and have eroded undermined edges. This is expressed clinically as abdominal pain, diarrhoea with blood in the faeces, and only moderate or no fever, with good general condition. When the rectum is affected there is tenesmus (painful cramps in the anus). Peri-anal ulcers may occur via direct spread from rectal amoebiasis. The ulcers develop rapidly and are painful. After suffering from amoebic colitis there may be persistent intestinal problems, the aetiology of which is unclear.

Fulminant colitis

There is sometimes a fulminant course with high fever, a severely ill patient, intestinal bleeding or perforation of the colon. A slow seepage of intestinal content into the peritoneum is very likely in a severely ill patient whose condition deteriorates progressively, together with the formation of ileus (intestinal paralysis) and a distended abdomen. A fulminant course may occur if patients are treated with steroids (e.g. if amoebic colitis is wrongly thought to be Crohn’s disease or haemorrhagic ulcerative colitis).

Amoeboma

In 1% of patients an inflammatory thickening of the intestinal wall occurs. A mass may then be palpated (amoeboma). The diagnosis may be made via biopsy. The inflammatory mass may mimick colon carcinoma. Countless trophozoites are found in the tissues (never cysts). Correct therapy produces a pronounced reduction in the volume in approximately 3 days.

Category: Medicine Notes