Amebic Liver Abscess

Amebic liver abscess forms when E. histolytica trophozoites enter the bloodstream from intestinal lesions and reach the liver, causing hepatic necrosis; it is actually a complication of amebic colitis. Main manifestations are prolonged fever, right upper abdominal or right lower chest pain, systemic wasting, tender hepatomegaly, and leukocytosis, and it can easily lead to thoracic complications. The ileocecal region and ascending colon are predilection sites for amebic colitis; parasites return via the superior mesenteric vein to the right hepatic lobe, which is larger and receives more blood, so over 90% of clinical abscesses are in the right lobe, especially the dome. In China, incidence is higher in the South, generally higher in rural than urban areas, higher in males than females, and occurs at age 30 to 40. Hepatic abscess complicates intestinal amebiasis in 1.8% to 20%, up to 67%.

Common Symptoms

Fever; hepatic metastasis; bloody purulent stool; low fever and fatigue; fatigue; low fever; remittent fever; liver pain

Causes and Pathogenesis

(1) Etiology: E. histolytica has trophozoite and cyst stages. In 1993, WHO formally named non-pathogenic strains E. dispar based on isoenzyme profiles, membrane antigens, and virulence proteins, while pathogenic strains remain E. histolytica. Trophozoites in fresh bloody mucoid stool or liver abscess aspirate are actively motile at 5 μm/s, reproduce by binary fission, and vary widely in form. In symptomatic patients' tissues, they often contain ingested red blood cells, measuring 20 to 40 μm, even 50 μm; in non-diarrheal luminal stool or bacterized media they are 10 to 30 μm without red blood cells. Ectoplasm and endoplasm are clearly demarcated; movement is via a single directional pseudopodium. The endoplasm has a vesicular spherical nucleus 4 to 7 μm in diameter, with a single layer of uniform peripheral chromatin granules, and a small nucleolus (only 0.5 μm), often central with fine filamentous structures. Cysts form in the intestinal lumen but not outside it; luminal trophozoites shrink, become spherical precysts, then uninucleate cysts divide by binary fission into mature 4-nucleated cysts 10 to 16 μm in diameter with a 125 to 150 nm wall. Scanning and transmission electron microscopy show the cell membrane is about 10 nm thick with a fuzzy glycocalyx; cytoplasm contains glycogen granules and helically arranged ribosomes, lacking typical mitochondria, rough ER, and Golgi. The membrane has many filamentous projections and 0.2 to 0.4 μm circular pores related to micropinocytosis, absent at pseudopodia and micropinocytosis canals, a characteristic of E. histolytica trophozoites. In vitro culture has progressed from xenic to monoxenic to axenic and clonal soft agar culture, enabling pure antigen production. Amebic liver abscess develops slowly after a long occult period following intestinal amebiasis; overeating can trigger intestinal inflammation and activate latent amebic infection; alcoholism and conditions reducing bodily resistance can precipitate hepatic abscess; reinfection can reactivate existing infection; corticosteroid use can also induce abscess. (2) Pathogenesis: Trophozoites in colonic ulcers enter the portal system via invasiveness to reach the liver, but can also directly invade through the bowel wall or via lymphatics. Most parasites reaching the liver are destroyed; only a few survive and multiply. Trophozoites cause local liquefactive necrosis in portal areas through embolism, histolysis, and division, forming abscesses; it takes over 1 month on average from invasion to abscess formation. Abscesses vary in depth; most are large single cavities, about 80% in the right lobe, especially the dome, because the right lobe receives blood from the cecum and ascending colon, the main intestinal lesions. Early on, multiple small abscesses are common due to hematogenous portal spread, later merging into a single large cavity. The center is a large necrotic area; the pus is liquefied liver tissue, chocolate sauce-like, viscous or thin, with a livery odor, containing dissolved and necrotic hepatocytes, red blood cells, white blood cells, fat, Charcot-Leyden crystals, and residual tissue. Trophozoites often aggregate on the cavity wall; about 1/3 of cases find trophozoites in pus, but cysts are never found. Abscesses can expand and become superficial, rupturing into adjacent cavities or organs. Chronic abscesses may develop secondary bacterial infection (E. coli, Staphylococcus, Proteus, Aerobacter, Alcaligenes), after which pus loses its typical character, becoming yellow or yellow-green, odorous, with abundant pus cells, and clinical toxemia may appear.

Treatment

Drug therapy, surgical treatment, supportive therapy

Preventive Measures

Strict fecal management, hygiene, and prompt treatment of amebic dysentery can prevent amebic liver abscess. Even if amebic hepatitis occurs, timely treatment can prevent abscess formation. With prompt and proper treatment, prognosis is good. Pay attention to personal and dietary hygiene: wash hands before meals and after using the toilet, drink boiled water, wash raw vegetables and fruits thoroughly and disinfect appropriately (e.g., vinegar or potassium permanganate soaking). Strengthen exercise, improve diet, and enhance resistance. Patients with amebic dysentery should seek early diagnosis and treatment with anti-parasitic drugs such as metronidazole and emetine hydrochloride to prevent liver abscess. Traditional Chinese medicines Brucea javanica and Pulsatilla chinensis also have preventive and therapeutic effects on acute and chronic intestinal amebiasis.

Department to Visit

It is recommended to visit the Rehabilitation department; an appointment can be booked on this platform before the visit.

Warm reminder: The above information is for health science reference only and cannot replace professional medical diagnosis. If you have related symptoms, please seek medical attention at a regular hospital promptly.