Occasionally, trophozoites perforate the intestinal wall. The release of intestinal contents into the abdominal cavity causes severe abdominal pain and an abdominal infection (peritonitis), which requires immediate medical attention.

Occasionally, the trophozoites spread through the bloodstream, causing infection in the lungs, brain, and other organs. The skin may also become infected, especially around the buttocks and genitals, as may wounds caused by surgery or other.