[Ameboma of the large intestine and rectum]

Amoeboma was diagnosed in three patients: a Bengal seaman aged 40 and two Dutch citizens who had lived in the tropics, a man aged 41 and a woman aged 56. The first-mentioned patient had a rectal tumour easily inspected by sigmoidoscopy; a biopsy sample contained Entamoeba histolytica. The faeces contained no cysts. The two other patients had coecal amoebomas. They had been operated elsewhere on suspicion of appendicitis and had been treated with metronidazole, which had failed to eliminate the amoebae. The faeces still contained cysts. One patient had trophozoites in a biopsy sample. The serum of all three patients contained anti-amoeba antibodies. Two patients were treated successfully with a combination of metronidazole (a tissue amoebicide) and diloxanide (a lumenal amoebicide). In one patient this combination failed, and emetine had to be substituted for the metronidazole, also because of an allergic reaction. Amoeboma of colon or rectum is one of the many manifestation forms of amoebiasis, but it is rare. While in amoebic colitis tissue necrosis (histolysis) is encountered almost exclusively, in amoeboma there is a violent inflammatory reaction with formation of a pseudotumour by granulation tissue, possibly due to secondary bacterial infection. Endoscopy and determination of circulating antibodies against the causative agent E. histolytica have by now improved the diagnosis so much that adequate treatment without surgical intervention is possible in principle. As with so many exotic diseases, a stay in the tropics is the key to the diagnosis.