Indications for Drainage of Hepatic Amebic Abscesses

 

Differential diagnosis of amebic liver abscess:

(1) pyogenic abscess: drainage is diagnostic and therapeutic

(2) echinococcal cyst: diagnosis based on calcifications in wall and serology

(3) hepatoma

 

Indications for needle aspiration under CT or ultrasound guidance:

(1) differential diagnosis of pyogenic vs amebic abscess, especially when multiple lesions present

(2) deterioration in clinical condition while on apparently adequate therapy and unable to wait for serologic studies, or for conversion of initially negative serologies

(3) high risk of rupture, especially left lobe abscess

(4) bacterial superinfection

(5) large juxta-cardiac abscesses, with risk of rupture into the pericardium

 

Indications for surgical drainage:

(1) abscess requiring drainage that cannot be reached percutaneously

(2) after rupture into the pericardium

(3) management of bacterial superinfection

 

Nonindications for drainage:

(1) noncompliance with medical therapy

(2) pregnancy

(3) increase in abscess size or development of an abnormal shape while on medical therapy with good clinical response

(4) persistence of cystic lesion after medical therapy with good clinical response

 

Limitations of drainage procedures:

• Conservative drug therapy is usually effective.

• Multiple percutaneous drainages or placement of a drain may occasionally result in bacterial superinfection.

• There is no good evidence that evacuation of large amebic lesions results in more rapid healing, unless the lesion is massive (occupies more than 50% of the liver).

• Surgical drainage is rarely performed today due to greater mortality when compared to conservative therapy.

• Rupture of an amebic abscess into the pleural or peritoneal cavity can usually be managed medically.

• Examination of the aspirated abscess contents shows amebae in the minority of cases, while the yield of amebic culture is low. Since organisms are at the periphery of the abscess, biopsy of the cyst wall may be needed to demonstrate the organisms.

• Drainage of an echinoccal cyst can be hazardous due to the risk of anaphylactic response or leakage of scolices into the peritoneum.

 

Serologic testing for antibodies is usually positive in patients with hepatic amebic abscess(es). However:

(1) Serology may be negative in patients with an acute presentation of less than 7 days. Repeat testing in a week usually will show conversion. The galactose adhesin antigen may be found in 75% of patients with amebic abscess and can be present before demonstration of antibody.

(2) Patients from endemic areas may have positive serologic tests due to antibodies developed from prior infection.