Single Solid mass in the Liver | Amoebic Abscess

Many different diseases may cause a solitary, solid mass in the liver. The differential diagnosis may be very difficult and many require biopsy. A solitary, well-defined hyperechogenic mass close to the liver capsule may be a hemangioma: 75% of haemangiomas have posterior acoustic enhancement without acoustic shadowing. but when large may lose hyperechogenicity and cannot be easily differentiated from a primary malignant liver tumor. Occasionally there will be multiple haemangiomas, but they do not usually produce clinical symptoms.

It can be very difficult to differentiate a hemangioma from a solitary metastasis, abscess, or hydatid cyst. A lack of clinical symptoms strongly suggests hemangioma. To confirm the diagnosis, either computerized tomography, angiography, magnetic resonance imaging, or radionuclide scanning with labeled red blood cells will be necessary. The absence of other cysts helps to exclude hydatid disease. If there has been an internal hemorrhage, the ultrasound images may resemble those of a necrotic abscess.

A single homogenous mass with a low-level echo around the periphery is probably a hepatoma. However, hepatomas may also present with central necrosis or as a diffuse mass, can be multiple, and may also infiltrate the portal or hepatic vein.

Liver abscess

It is very different between a bacterial abscess, an amoebic abscess, and an infected cyst. All may be either multiple or single, and usually present as hypoechogenic masses with strong back walls, irregular outline, and internal debris. There may be internal gas. Bacterial infection may also occur in an inactive amoebic abscess or in a healed amoebic abscess cavity. A necrotic tumor or a hematoma can also resemble an abscess.

Amoebic abscess

In the early stages, an amoebic abscess may be echogenic, with poor edge definition, or even isodense and not visible. It will later appear as a mass with irregular walls and with acoustic enhancement. There is usually internal debris. As the infection progresses, the abscess may become well demarcated with a sharper outline: the debris may be finer. The same changes occur after successful treatment but the abscess cavity may remain for several years and be confused with a cystic mass. The scar of a healed amoebic abscess persists indefinitely and may eventually calcify.

Amoebic abscesses in the liver

• Usually solitary but may be multiple and of different sizes.
• More frequently in the right lobe of the liver.
• Usually near the diaphragm but can be anywhere.
• Respond to metronidazole or other appropriate treatment.
• Maybe isodense and invisible on the first scan. If suspected clinically, repeat the scan after 24 and 48 hours.
• Cannot be differentiated reliably from pyogenic abscesses.