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Clinical Characteristics

The clinical spectrum of amebiasis is very wide: some patients have no symptoms while others may be desperately ill. Amebiasis can remain clinically silent and, in endemic areas, may be found incidentally at autopsy. Patients may be totally unaware of the invasive stage, and thus the history may be quite unreliable. There may have been no episode of dysentery, or it may have been so mild or occurred so long ago that it is overlooked. However, with invasive amebiasis, symptoms usually develop and may occur as early as 8 to 11 days after infection, but more commonly the interval is much longer and the patient may even remain symptom free for months or years.

Similarly, the course of the disease is also variable: there may be mild abdominal discomfort or acute dysentery with gripping abdominal pain, tenderness, and fever. Some patients have alternating constipation and diarrhea, whereas others have no clinical features of colonic infection. The initial attack may subside spontaneously after several days or may persist for weeks. Alternating periods of remission and exacerbation may continue for years in chronic amebic colitis. An unsuspected liver abscess may be discovered when there has been minor trauma to the rib cage, causing the abscess to rupture into the chest or abdomen and present as an acute emergency. In other patients, a lung abscess, pneumonia, or pleurisy may first bring the patient to medical attention.

Gastrointestinal invasion is more common among children, while hepatic amebiasis is more frequently seen in adults, with a 3 or 4:1 male to female ratio. There is less incidence of invasive amebiasis during pregnancy; however, it becomes more serious during the postpartum stage. It is more common among the malnourished and immunosuppressed, usually with grave consequences. The mortality is less than 1% in children with intestinal dysenteric amebiasis, but increases to 21.3% to 40.2% when the course is complicated by intestinal perforation and peritonitis. Mortality from treated hepatic amebic abscess has gradually diminished from 2.0% to 0.2%, although it remains at 10.3% in some rural areas of Mexico.

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