World J. Surg. 14, 498-504, 1990 0 World Journal of Surgery 9 1990 by the Soci~t~ Internationale de Chirurgie Surgical Management of Hepatic Abscesses Henry A. Pitt, M.D. Department of Surgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland, U.S.A. Amebic and pyogenic hepatic abscesses are rare liver lesions that may require surgical intervention. Amebic liver abscesses are more common in subtropical and tropical climates and in areas with poor sanitation. The majority of pyogenic liver abscesses are caused by infections in the biliary or intestinal tracts. These lesions can be differentiated on clinical grounds and by amebic serology. Ultrasound and computed tomography are the imaging techniques of choice. The initial management of amebic hepatic abscesses is treatment with amebicidal agents. Most patients respond rapidly so that surgery is reserved for patients with complications including secondary bacterial infection, impending rupture, or rupture into the pericardium or peritoneum. Patients with pyogenic hepatic abscesses require a prolonged course of antibiotics and appropriate drainage. Selected solitary abscesses can be managed with percutaneous abscess drainage. Similarly, some abscesses of biliary origin wili respond to percutaneous biliary drainage. Surgical drainage has several advan- tages including: the ability to explore the abdomen for a source, excellent exposure of the entire liver, accurate assessment, sometimes with ultra- sound, of the best drainage site, and access to the biliary tree for cholangiography and drainage. Both amebic and pyogenic intrahepatic abscesses are rare, life-threatening entities. Patient survival depends on early diag- nosis and prompt treatment. Various factors including newer imaging modalities, improved amebicidal agents and antibiot- ics, availability of guided percutaneous aspiration and drainage techniques, and improved anesthetic, surgical, and postopera- tive management have improved survival of patients with intrahepatic abscesses. Nevertheless, the diagnosis remains diflicult, and the differentiation of amebic and pyogenic ab- scesses can present a challenge. Moreover, debate continues regarding the appropriateness of nonoperative and operative therapy. Etiology and Pathogenesis Amebic Abscess Amebiasis has a worldwide distribution with the highest inci- dence being found in subtropical and tropical climates and in areas with poor sanitation. Entamoeba histolytica in the cystic Reprint requests: Henry A. Pitt, M.D., Professor of Surgery, The Johns Hopkins Hospital, Blalock 688, 600 North Wolfe Street, Balti- more, Maryland 21205, U.S.A. form gains access into the body by oral ingestion of infected material which is usually contaminated water. The mature cysts are resistant to an acid pli and drying and, thus, pass un- changed through the stomach into the small intestine. The cyst wall is then digested by pancreatic enzymes releasing the invasive trophozoites. Trophozoites live and multiply in the lumen of the large intestine, especially the cecum. They may pass into the distal colon and change into round or oval cysts which pass in the feces as resistant cysts. Human carriers who pass cysts of Entamoeba histolytica in their stools are the primary source of infection. Entamoeba histolytica may live within the lumen of the colon without tissue invasion. When tissue invasion occurs, superfi- cial mucosal ulceration may be seen where trophozoites have entered the mucosa. Amebic trophozoites may enter the mes- enteric venules or lymphatics and be carried to the liver, lungs, or other organs. The most frequent site of extraintestinal colonization is the liver. If sufficient numbers of amebic tropho- zoites enter the liver and become lodged in smaller venules, thrombosis and infarction of small areas of hepatic parenchyma occur. Development of an amebic liver abscess presumably results from coalition of a number of small areas of necrosis and amebic cytolytic destruction of hepatic parenchyma. Pyogenic Abscess The majority of pyogenic liver abscesses are caused by infec- tion in the biliary or intestinal tracts. The etiology of liver abscesses can be conveniently divided into 6 categories based on the route of extension of infection. These etiologic catego- ries include the following sources of infection: (1) Biliary--from ascending cholangitis, (2) Portal vein--as in pylephlebitis re- sulting from appendicitis or diverticulitis, (3) Hepatic artery-- from septicemia, (4) Direct extension--from a contiguous dis- ease process, (5) Traumatic from blunt or penetrating injuries, and (6) Cryptogenic--when no primary source of infection is found. Prior to the introduction of antibiotics, appendicitis and other intraabdominal infections resulting in pylephlebitis were the leading causes of pyogenic hepatic abscess. In a collected series of 622 patients published by Ochsner and colleagues [1] in 1938, the route of infection was via the portal vein in 43% and via the biliary tree in only 14% of their patients (Fig. 1). Appendicitis