Amebiasis is an infectious disease caused by the protozoan Entamoeba histolytica. Worldwide in distribution, it affects 20% of the world population. However, it is most widespread in the tropical countries. The distribution is 0-10% in the northern countries and 5-60% in the tropics. Many of the reported cases in non-tropical countries usually are cases of patients who have visited those areas. Hepatic abscess is the most frequent manifestation of extra-intestinal disease.
Ultrasound has proven to be an excellent method for the diagnosis of hepatic abscess. Amebic hepatic abscesses generally present as a solitary lesion, but they can also be multifocal, usually with poorly defined or shaggy walls. When lesions become visible to ultrasound, they generally have a round or oval shape, and are mostly localized in the periphery of the right lobe. They are typically hypoechoic with fluid content or may present with a complex internal echo pattern (depending on the degree of liquefaction). These lesions exhibit some degree of posterior acoustic enhancement in 70–80% of cases.
The abscess cavity may last for weeks or months after medical treatment has been completed, with an average of seven months. In some cases ultrasonographic changes can persist for 12 months and more, without clinical significance.