| disease | Amebic Liver Abscess |
| alias | Amebic Liver Abscess |
Amebic liver abscess is the most common complication of amebic intestinal disease, characterized by prolonged fever, pain in the right upper abdomen or lower right chest, systemic wasting, liver enlargement with tenderness, leukocytosis, and a tendency to cause thoracic complications.
bubble_chart Clinical Manifestations
It is related to the course of the disease, the size and location of the abscess, and the presence of complications. Most cases have a gradual onset, with symptoms such as irregular fever, night sweats, etc. The fever is mostly intermittent or remittent, and when complications occur, the temperature often rises above 39°C and may present as a biphasic fever. The temperature usually rises in the afternoon, peaks in the evening, and is accompanied by profuse sweating when the fever subsides at night. Patients often experience symptoms such as loss of appetite, abdominal distension and fullness, nausea, vomiting, diarrhea, and dysentery. Liver pain is an important symptom of this disease, typically presenting as persistent dull pain that worsens with deep breathing and changes in body position, often becoming more noticeable at night. Abscesses in the upper right lobe can irritate the right diaphragm, causing right shoulder pain, or compress the lower right lung, leading to signs of pneumonia or pleuritis, such as shortness of breath, cough, dullness at the lung base, moist rales at the lung base, and pleural friction rub in the axillary region. Abscesses located in the lower part of the liver may cause right upper abdominal pain and right lumbago. Some patients experience fullness in the right lower chest or right upper abdomen, or palpable masses with tenderness. Left lobe liver abscesses account for about 10% of cases, with patients experiencing mid-upper or left upper abdominal pain radiating to the left shoulder, hepatomegaly below the xiphoid process, or fullness, tenderness, muscle tension, and liver percussion pain in the mid or left upper abdomen. The liver often presents with diffuse enlargement, with obvious localized tenderness and percussion pain at the site of the lesion. The lower edge of the liver is blunt and rounded, with a solid feel and medium firmness. Some patients may have localized fluctuation in the liver area. Jaundice is rare and usually mild, with a higher incidence in cases of multiple abscesses.
Chronic sexually transmitted disease cases may present with exhaustion, emaciation, anemia, and nutritional edema, with fever being less noticeable. Some advanced-stage patients may have a firm, enlarged liver with localized protrusion, easily mistaken for liver cancer.bubble_chart Auxiliary Examination
(1) Blood Test In the acute phase, the total white blood cell count is moderately elevated (grade II), with neutrophils accounting for about 80%. This increases further in cases of secondary infection. In prolonged cases, the white blood cell count mostly approaches normal or decreases, anemia becomes more pronounced, and the erythrocyte sedimentation rate (ESR) increases.
(2) Stool Examination A minority of patients may test positive for Entamoeba histolytica.
(3) Liver Function Tests Elevated alkaline phosphatase is the most common finding, while cholesterol and albumin levels are mostly reduced. Other indicators are generally normal.
(4) Serological Tests Similar to amebic intestinal disease, the antibody positivity rate can exceed 90%. A negative result essentially rules out the disease.
(5) Liver Imaging Ultrasound examination is non-invasive, accurate, and convenient, making it the fundamental method for diagnosing liver abscesses. The abscess location shows a fluid level segment roughly corresponding to the abscess size. It can also guide puncture or surgical drainage and monitor the progression of the abscess cavity through repeated examinations. B-mode ultrasound imaging is highly sensitive but may be difficult to distinguish from other fluid-containing lesions, requiring dynamic observation.
CT, hepatic angiography, radionuclide liver scanning, and magnetic resonance imaging (MRI) can all reveal space-occupying lesions in the liver. These methods aid in differentiating amebic liver disease from liver cancer and hepatic cysts. Among them, CT is particularly convenient and reliable and may be selected if available.
(6) X-ray Examination Common findings include elevation and restricted movement of the right diaphragm, pleural reaction or effusion, and hazy shadows at the lung base. For abscesses in the left lobe of the liver, a barium meal examination may show compression of the lesser curvature of the stomach or displacement of the duodenum. A lateral view may reveal bulging of the anterior medial right rib, causing the disappearance of the cardiophrenic or anterior costophrenic angle. Occasionally, irregular translucent fluid-gas shadows in the liver area on plain films are highly characteristic.
The key clinical diagnostic points for liver abscess are: ① right upper abdominal pain, fever, hepatomegaly, and tenderness; ② X-ray showing elevation and reduced movement of the right diaphragm; ③ ultrasound revealing a fluid-filled segment in the liver area. A definitive diagnosis of amebic liver abscess can be made if typical pus is obtained through liver puncture, amebic trophozoites are found in the pus, or there is a favorable response to specific anti-amebic drug therapy.
bubble_chart Treatment Measures
(1) Medical Treatment
1. Anti-amoebic Therapy The primary approach involves using tissue-acting amoebicides, supplemented by intestinal-acting amoebicides to achieve a cure (see "Amoebic Intestinal Disease"). Currently, metronidazole is the first-line treatment, with a dose of 1.2g/day for 10–30 days, achieving a cure rate of over 90%. In uncomplicated cases, symptoms such as liver pain and fever show significant improvement within 72 hours of medication, with fever subsiding within 6–9 days. Hepatomegaly, tenderness, and leukocytosis typically resolve within about 2 weeks of treatment, while abscess cavities may take up to 4 months to absorb. Second-generation nitroimidazole drugs exhibit similar anti-parasitic activity and pharmacokinetics to metronidazole but have a longer half-life, making them more effective for abscesses than for amoebic intestinal disease. In Southeast Asia, short-course (1–3 days) therapy is employed and can replace metronidazole. For the few cases where metronidazole is ineffective, chloroquine or emetine may be used, though the former has a higher relapse rate and the latter carries more cardiovascular and gastrointestinal side effects. In the late stage [third stage], a course of intestinal anti-amoebic drugs is routinely added to eliminate potential compound infections.
2. Liver Puncture and Drainage With early effective drug therapy, many liver abscesses no longer require puncture. However, puncture drainage is indicated if there is no significant clinical improvement after 5–7 days of appropriate drug therapy, or if there is prominent local liver bulging, marked tenderness, or risk of rupture. Puncture is best performed 2–4 days after initiating anti-amoebic therapy. The puncture site is usually selected at the 8th or 9th intercostal space along the right anterior axillary line, or the 9th or 10th intercostal space along the right midaxillary line, or at the point of maximal bulging and tenderness in the liver area, preferably under ultrasound guidance. The frequency of puncture depends on clinical need, with each session aiming to fully aspirate the pus. For abscesses with over 200ml of pus, repeat aspiration is often required after 3–5 days. Large abscess cavities may heal faster with aspiration. Recent advances in interventional therapy allow for continuous closed drainage via needle guidance, eliminating the drawbacks of repeated punctures and secondary infections, and should be adopted where feasible.
(2) Surgical Treatment Less than 5% of liver abscesses require surgical drainage. Indications include: ① Failure of anti-amoebic therapy and puncture drainage; ② Abscesses in high-risk locations near the liver hilum, major blood vessels, or deep (>8cm), where puncture risks injury to adjacent organs; ③ Abscess rupture into the peritoneal cavity or adjacent organs with inadequate drainage; ④ Secondary bacterial infection unresponsive to drug therapy; ⑤ Multiple abscesses making puncture drainage difficult or ineffective; ⑥ Left lobe abscesses, which risk pericardial rupture and peritoneal contamination during puncture, also warrant surgical consideration.
The criteria for cure of liver abscesses are not uniform, but clinical cure is generally defined by the disappearance of symptoms and signs. Filling defects in liver abscesses mostly resolve completely within 6 months, though 10% may persist for up to a year. Larger lesions may leave residual liver cysts. Erythrocyte sedimentation rate (ESR) can also serve as a reference indicator.
The main complications of amoebic liver abscess are secondary bacterial infection and rupture into surrounding tissues. Secondary bacterial infection is characterized by pronounced shivering, high fever, aggravated toxemia, and a significant increase in total white blood cell count and neutrophils. The pus appears yellow-green or foul-smelling, with a large number of pus cells visible under microscopy, but the bacterial culture positivity rate is low. Amoebic liver abscess may rupture into adjacent organs, such as perforating the diaphragm to form empyema or lung abscess, rupturing into the bronchus to cause pleuropulmonary-bronchial fistula, or perforating into the pericardium or abdominal cavity, leading to pericarditis or peritonitis. It may also rupture into the stomach, large intestine, inferior vena cava, common bile duct, right renal pelvis, and other sites, causing amoebiasis in various organs. Except for rupture into the gastrointestinal tract or the formation of hepatobronchial fistula, the prognosis is generally poor.
Only 40% of amoebic liver abscesses confirmed by pathology abroad are diagnosed before death, while the clinical misdiagnosis rate in China in recent years ranges from 17% to 38.5%. This disease should be differentiated from the following conditions.
(1) Primary liver cancer: Clinical manifestations such as fever, weight loss, right upper abdominal pain, and hepatomegaly closely resemble those of amoebic liver abscess. However, the latter often presents with higher fever, more severe liver pain, and a harder, nodular liver texture. Tests such as alpha-fetoprotein measurement, B-ultrasound, abdominal CT, radioactive isotope liver scanning, selective hepatic angiography, and magnetic resonance imaging can clarify the diagnosis. Liver puncture and a therapeutic trial with anti-amoebic drugs may aid in differentiation.
(2) Bacterial liver abscess: Key points for differentiating bacterial liver abscess from amoebic liver abscess are shown in Table (11-51).
Table 11-51 Differentiation between Amoebic Liver Abscess and Bacterial Liver Abscess
| Amebic Liver Abscess | Bacterial Liver Abscess | |
| History | History of amoebic colitis | Often occurs after sepsis or abdominal suppurative diseases |
| Symptoms | Slow onset, prolonged course | Acute onset, marked toxic symptoms such as shivering, high fever, shock, jaundice |
| Liver | Significant enlargement and tenderness, possible local bulging, abscess usually large and solitary, often in the right lobe | Less significant enlargement, milder local tenderness, generally no local bulging, abscesses often small and multiple |
| Liver Puncture | Large amount of pus, mostly brownish, amoebic trophozoites may be found | Small amount of pus, yellowish-white, bacterial culture may be positive, pathological examination of liver tissue shows suppurative changes |
| Blood Test | Mild to moderate leukocytosis, negative bacterial culture | Marked leukocytosis, especially neutrophils, bacterial culture may be positive |
| Amoebic Antibody | Positive | Negative |
| Treatment Response | Effective with metronidazole, chloroquine, emetine, etc. | Effective with antibiotics |
| Prognosis | Relatively better | Prone to recurrence |
(3) Schistosomiasis: In schistosomiasis-endemic areas, hepatic amoebiasis is often misdiagnosed as acute schistosomiasis. Both present with fever, diarrhea, and hepatomegaly, but the latter has milder liver pain, more prominent splenomegaly, and significant eosinophilia in blood tests. Stool hatching, sigmoidoscopy, and soluble egg antigen detection can aid in differentiation.
(4) Cholecystitis: Acute onset with paroxysmal exacerbation of right upper abdominal pain, often with a history of recurrent episodes. Jaundice is more common and severe, hepatomegaly is less prominent, and there is marked tenderness in the gallbladder area. Cholecystography and duodenal drainage can help differentiate.
