Extra-intestinal amebiasis: clinical presentation in a non-endemic setting

Amebic liver abscess

Amebic liver abscess is the most common extraintestinal manifestation of infection with Entamoeba histolytica, and it is associated with significant morbidity and mortality. In this article the most recent available information is reviewed relating to epidemiology, pathogenesis, presentation, diagnosis, and treatment. We reviewed thousands of cases of amebic liver abscess in the medical literature and present that information as it pertains to mortality, gender, anatomic location of abscesses, and clinical signs and symptoms.

Thoracic amebiasis

Pleuropulmonary amebiasis is the common and pericardial amebiasis the rare form of thoracic amebiasis. Low socioeconomic conditions, malnutrition, chronic alcoholism, and ASD with left to right shunt are contributing factors to the development of pulmonary amebiasis. Although no age is exempt, it commonly occurs in patients aged 20 to 40 years, with an adult male to female ratio of 10:1. Children rarely develop thoracic amebiasis: when it does occur there is an equal sex distribution. The infection usually spreads to the lungs by extension of an amebic liver abscess. Infection may pass to the thorax directly from the primary intestinal lesion through hematogenous spread, however. Lymphatic spread is one possible route. Inhalation of dust containing cysts and aspiration of cysts or trophozoites of E histolytica in the lungs are some other hypothetical routes. The lung is the second most common extraintestinal site of amebic involvement after the liver. Usually the lower lobe, and sometimes the middle lobe of the right lung, are affected, but it may affect any lobe of the lungs. The patient develops fever and right upper quadrant pain that is referred to the tip of the right shoulder or in between the scapula. Hemophtysis is common. The diagnosis of thoracic amebiasis is suggested by the combination of an elevated hemidiaphragm (usually right), hepatomegaly, pleural effusion, and involvement of the right lung base in the form of haziness and obliteration of costophrenic and costodiaphragmatic angles. Infection is usually extended to the thorax by perforation of a hepatic abscess through the diaphragm and across an obliterated pleural space, producing pulmonary consolidation, abscesses, or broncho-hepatic fistula. Empyema develops when a liver abscess ruptures into the pleural space. Rarely, a posterior amebic liver abscess can burst into the inferior vena cava and develop an embolism of the inferior vena cava and thromboembolic disease of the lungs with congestive cardiac failure or corpulmonale. Diagnosis by finding E histolytica in stool specimens is of limited value. In a limited number of cases amebae might be found in aspirated pus or expectorated sputum. "Anchovy sauce-like" pus or sputum may be found. Presence of bile in sputum indicates that the pus is of liver origin. Serological tests are of immense value in diagnosis. Liver enzymes are usually normal and neutrophilic leucocytosis may or may not be found. ESR is invariably elevated. Anti-amebic antibodies can be detected by ELISA, IFAT, and IHA. Amebic antigen can be detected from serum and pus by ELISA. Detection of Entamoeba DNA in pus or sputum may be a sensitive and specific method. Pleuropulmonary amebiasis is easily confused with other illnesses and is treated as pulmonary TB, bacterial lung abscesses, and carcinoma of the lung. A single drug regimen with metronidazole with supportive therapy usually cures patients without residual anomalies. Aspiration of pus from empyema thoracis may be needed for confirmation and therapeutic purposes. The pericardium is usually involved by direct extension from the amebic abscess of the left lobe of the liver, sometimes from the right lobe of the liver, and rarely from the lungs or pleura. An initial accumulation of serous fluid due to reactive pericarditis followed by intrapericardial rupture may develop either (1) acute onset of severe symptoms with chest pain, dyspnea, and cardiac tamponade, shock, and death, or (2) progressive effusion with thoracic cage pain, progressive dyspnea, and fever. Chest radiograph, ultrasound examination, and CT scan usually confirm the presence of a liver abscess in continuity with the pericardium and fluid within the pericardial sac with or without the fistulous tract. Echocardiography may demonstrate fluid in the pericardial cavity. Patients should be cared for in the ICU and ambecides should be started without delay. Pericardiocentesis usually confirms the diagnosis and improves the general condition of the patient. Aspiration of the accumulated fluid should be performed urgently in cardiac tamponade; repeated aspiration may be needed. Surgical drainage should be done if needed. Acanthamoeba, a free-living ameba, may also infect the lungs in the form of pulmonary nodular infiltration and pulmonary edema in association with amebic meningoencephalitis in immunocompromised patients. It usually spreads to the meninges of the brain by way of the blood from its primary lesion in the lung or skin. Early diagnosis and institution of treatment may be life saving for these patients. A literature review shows that HIV/AIDS patients are not prone to infection with E histolytica. It is now clear that there are an increasing number of HIV-seropositive patients among amebic liver abscess patients, however, which suggests that although the incidence of intestinal infection is not high among HIV-seropositive or AIDS patients they are more susceptible to an invasive form of the disease.

Amebic liver abscess

Amebiasis is a widespread parasitic disease caused by Entamoeba histolytica. This protozoan organism is the third leading parasitic cause of death in the developing world and is an important health risk to travelers in endemic areas. Amebiasis most commonly results in asymptomatic colonization of the gastrointestinal tract, but some patients may develop intestinal invasive disease or extraintestinal disease-amebic liver abscess being the most common extraintestinal manifestation. This article reviews epidemiologic features, pathophysiology, clinical features, diagnostic tests, imaging studies, treatment of amebic liver abscess, and prevention measures.

Common presentations of amebic liver abscess

STUDY OBJECTIVE

The most common extraintestinal manifestation of Entamoeba histolytica, the agent of amebiasis, is a hepatic abscess. This infection is common throughout the world and can be associated with life-threatening consequences. Given the often nonspecific nature of the complaints related to an amebic abscess, a retrospective review of patients with confirmed disease was done to recognize the most common patterns of presentation.

METHODS

A retrospective case series was conducted of all patients with confirmed amebic liver abscess over a 5-year period. All available emergency department and inpatient records were reviewed. Age, sex, country of origin, chief complaint (including duration), vital signs, and physical and laboratory findings were recorded. The use of ultrasonography, computed tomography scan, chest radiograph, and serum antibodies was noted, as well as the final ED diagnosis.

RESULTS

Seventy-five patients were reviewed; mean patient age was 35.5 years, 80% were male, and Mexico was the country of origin for 64%. The most common complaint was fever (77%), followed by abdominal pain (72%), which was most often located in the right upper quadrant. Cough (16%), chest pain (19%), and chest radiographic abnormalities (57%) were also common. The majority of patients (69%) had symptoms for less than 13 days. The WBC count was the most consistent laboratory abnormality (83%), whereas the liver aminotransferase, alkaline phosphatase, and bilirubin levels were often normal. Most patients received their diagnoses on the basis of ultrasonography (85%), followed by a confirmatory serum antibody titer (88%). The diagnosis of amebic liver abscess was correctly made in the ED in 31.5% of the patients, with the most common misdiagnoses being cholecystitis (16.4%), hepatitis (12.3%), and pneumonia (9.6%).

CONCLUSION

Patients with amebic liver abscess do present to EDs in the southwestern United States, especially in areas with a high immigrant population from endemic areas. Patients with complaints of fever and right upper quadrant abdominal pain, especially men of Hispanic origin, warrant a high degree of vigilance. Whereas most laboratory studies are unhelpful, the diagnosis can often be made in the ED by means of a bedside ultrasonographic test. Treatment should be initiated with metronidazole with disposition to an inpatient medical service.