Amoebiasis is a common parasitic infection in developing countries with a worldwide distribution. The disease is caused by Entamoeba histolytica through ingestion of fecally contaminated water or food. Infection is self limiting in many cases, but can result in invasive disease, including intestinal and extra-intestinal manifestations .
Liver abscess is the most common extra-intestinal manifestation. Amebic abscess normally presents as an acute or subacute condition. Symptoms and signs include fever, abdominal tenderness, and hepatomegaly. Bowel symptoms are often absent and stool microscopy is negative for most patients. Usually abscess is single and occurs in right lobe . The involvement of diaphragmatic surface is not usual and leads to pleuritic pain and diaphragm elevation.
Diagnosis may be difficult in limited resource setting. Antigen and antibodies detection in the serum (tests with high sensitivity) are unavailable due to high cost. Microscopic examination of stool and abscess fluid is often available, but is limited by low sensitivity.
Ultrasound is a useful tool for detecting liver abscess with accuracy comparable to computed tomography. Amebic abscess normally appears as hypoechoic, homogeneous, round or oval lesion, with a hyperechoic wall and location generally contiguous with the liver capsule . Differential diagnosis, include echinococcal cyst, pyogenic abscess and hepatoma.
Furthermore, ultrasound allows in performing percutaneous drainage. In scarce resource scenarios, drainage may be useful for both diagnosis of liver lesions and therapeutic purposes. Fluid abscess contains necrotic material with few cells and appears as an odorless dark reddish-brown fluid (classically described as “anchovy paste”). Percutaneous drainage may be obtained with needle aspiration or catheter drainage. Complications include hemorrhage, bowel transfission, abscess-peritoneum communication and sepsis. In a large series of ultrasound-guided drainage of abdominal abscesses, the frequency of complications was low (6.6%) and mostly related to catheter drainage rather than needle aspiration . Therapeutic drainage is indicated for complicated abscesses (lesions localized in left lobe, multiple, with large diameter or with bacterial coinfection) and for non-responding abscesses. For uncomplicated abscesses, the role of therapeutic aspiration remains to be controversial .
In the present case, clinical and microbiological findings have not been sufficiently adequate to obtain the diagnosis. Goal-directed ultrasound, even performed by non-radiologist physician, plays a key role in diagnosis and clinical care revealing liver lesion and allowing in administering the appropriate medical therapy. Ultrasound-guided percutaneous aspiration was performed without complications and revealed a fluid abscess with features consistent with amebic abscess. However, percutaneous drainage for uncomplicated abscess is questionable.