Liver Abscess Workup

Laboratory studies may include a complete blood count (CBC) with differential (to identify anemia of chronic disease or neutrophilic leukocytosis) and liver function studies (hypoalbuminemia and elevation of alkaline phosphatase are the most common abnormalities; elevations of transaminase and bilirubin levels are variable.

Blood cultures are positive in roughly 50% of cases. Culture of abscess fluid should be the goal in establishing microbiologic diagnosis.

Enzyme immunoassay should be performed to detect E histolytica in patients either from endemic areas or who have traveled to endemic areas.

Advances in radiologic techniques has been credited with the improvement in mortality. The various radiologic techniques have differing benefits and limitations with regard to their diagnostic utility (see the image below).

Computed tomography

Computed tomography (CT) with contrast and ultrasonography remain the radiologic modalities of choice as screening procedures and also can be used as techniques for guiding percutaneous aspiration and drainage.

With advancements in multidetector CT technology, image quality has improved dramatically, allowing improved detection. CT has a sensitivity of 95-100% in this setting (see the images below).

Lesions on CT evaluation are well-demarcated areas hypodense to the surrounding hepatic parenchyma. Peripheral enhancement is seen when intravenous (IV) contrast is administered. Gas can be seen in as many as 20% of lesions.

CT is superior in its ability to detect lesions less than 1 cm. This technique also enables evaluation for an underlying concurrent pathology throughout the abdomen and pelvis. Indium-labeled white blood cell (WBC) scans are somewhat more sensitive in this regard.

A retrospective study was undertaken using patient records from a group of 131 patients with confirmed pyogenic liver abscesses to determine CT scan characteristics of those abscesses caused by monomicrobial K pneumoniae infection versus other causes. A comparison was performed between the K pneumoniae liver abscess patients and a comparison group. Notably, only 70.2% of the cases were determined to be monomicrobial K pneumoniae liver abscesses. CT scan characteristics more likely to be seen in these monomicrobial liver abscesses were (1) a single abscess, (2) unilobar involvement, (3) solid appearance, (4) association with thrombophlebitis, and (5) hematogenous appearance. ^[8]

Ultrasonography

Ultrasonographic evaluation (sensitivity, 80-90%) reveals hypoechoic masses with irregularly shaped borders. Internal septations or cavity debris may be detected. ^[9]  It allows close evaluation of the biliary tree and simultaneous aspiration of the cavity. The major benefits of this modality are its portability and diagnostic utility in patients who are too critical to undergo prolonged radiologic evaluation or to be moved out of monitored setting. Operator dependence affects its overall sensitivity.

Radionuclide scanning

The initial studies are used in diagnosis. ^[10]  Gallium and technetium radionuclide scanning use the fact that the radiopharmaceuticals share the same uptake, transport, and excretion pathways as bilirubin and, thus, are effective agents in evaluating liver disease. Sensitivity varies with the radiopharmaceutical utilized, technetium (80%), gallium (50-80%), and indium (90%). Limitations include a delay in diagnosis and the need for confirmatory procedures; thus, they offer no benefit over other imaging modalities.

Chest radiography

Chest radiographic findings of basilar atelectasis, right hemidiaphragm elevation, and right pleural effusion are present in approximately 50% of cases; before advancements in radiologic technique, these served as diagnostic clues. Pneumonias or pleural diseases often are initially considered because of the radiographic findings.

Percutaneous needle aspiration

Under CT or ultrasonographic guidance, needle aspiration of cavity material can be performed. Needle aspiration enables rapid recovery of material for microbiologic and pathologic evaluation. It can be performed with the initial diagnostic procedure.

Percutaneous catheter drainage

Percutaneous drainage has become the standard of care and should be the first intervention considered for small cysts. Advantages include reduced costs, recovery time, and postprocedure recovery rate; it eliminates the need for general anesthesia. This also allows for gradual, controlled drainage. For cysts larger than 5 cm, ruptured cysts, and multiloculated cysts, surgical drainage is generally recommended over percutaneous intervention.

A catheter is placed under ultrasonographic or CT guidance via the Seldinger or trocar techniques. The catheter is flushed daily until output is less than 10 mL/day or cavity collapse is documented by serial CT.

Multiple abscesses have been drained successfully by this method. Failure to respond to catheter drainage is the main reported complication and is also an indication for surgical intervention. Other complications reported (rarely) are bleeding at the catheter site, perforation of hollow viscus, and peritonitis from intraperitoneal spillage of cavity fluid.

Contraindications include coagulopathy; a difficult access path to the cavity; peritonitis; and/or a complicated, multiloculated, thick-walled abscess with viscous pus.