AMEBIC LIVER ABSCESS (Part Two)

AMEBIC LIVER ABSCESS (Cont.)

Complications

• The reported incidence of complications of amebic hepatic abscess varies from 20 to 35%.
  
• In analyzing 180 personal cases of amebic liver abscess, Ochsner and De-Bakey reported that 39 of their patients (22%) had a complication.
  
• Mortality was 41% in these 39 patients compared with only 9% among the 141 patients who did not develop a complication.
  
• In a more recent series, however, Adams and MacLeod reported that complications developed in only 215 of 2,074 cases (10%), and mortality was only 12% in the patients with complications.
  
• Most complications that occur in patients with an amebic liver abscess are related to rupture of the abscess into an organ or adjacent space.

Pleuropulmonary Complications

• The most common complications of amebic liver abscesses are those involving the pleura and lung.
  
• These complications included
  
• pleural effusion (15%),
  
• empyema (7%),
  
• perforated diaphragm (5%),
  
• pneumonitis (4.5%), and
  
• lung abscess (1.5%).
  
• Management of these patients varies, depending on the exact nature of the pleural or pulmonary problem.
  
• However, in analyzing the results of treatment of 31 patients with empyema resulting from an amebic liver abscess, Rasaretnan and associates suggested that tube thoracostomy may not be sufficient in many patients because of the rapid development of a thick membrane.
  
• Therefore, these authors recommended thoracotomy and decortication for most patients with empyema. Transudative pleural effusion or pneumonitis, in contrast, does not require surgical intervention.

Rupture into the Peritoneum

Ramachandran and Goonatillake found intraperitoneal rupture or "prerupture" in 16 of 80 patients (20%).

• These authors described the following modes of presentation in these patients:
  
• (1) generalized peritonitis,
  
• (2) localized peritonitis, and
  
• (3) pain, distention, and ileus without peritonitis ("prerupture").
  
• These authors recommended laparotomy with surgical drainage of the liver abscess and the use of a tissue amebicide such as metronidazole.

Erosion of an amebic abscess into the intestinal tract or through the abdominal wall is even less common than rupture into the peritoneal cavity.

• Adams and MacLeod reported rupture into the bowel in only 2 of their 2,074 South African patients (0.1%). However, both these patients died.
  
• Erosion through the skin of the flank or abdomen also occurs infrequently, but the consequences are slightly less devastating.

Rupture into the Pericardium

Erosion, usually from the left lobe, into the pericardium is the most dangerous complication of amebic hepatic abscess.

• Fortunately, this complication is uncommon.
  
• A low incidence was reported by Crane and associates (1.5%) and by Balasegaram (1.9%).
  
• Adams and MacLeod described the following modes of presentation:
  
• (1) hepatic,
  
• (2) cardiac, and
  
• (3) in shock.
  
• Eight of 27 patients (30%) initially presented with signs and symptoms of hepatic abscess, most often in the left lobe, and subsequently deteriorated and developed pericarditis.
  
• Two thirds of the patients in this study, however, first presented with cardiac signs, with inconspicuous symptoms and signs of the causative liver abscess.
  
• These 18 patients presented with the symptoms of pericarditis with effusion, congestive heart failure, or both.
  
• The onset of symptoms was gradual and frequently mimicked tuberculous pericarditis or congestive cardiomyopathy.
  
• Only 1 of 27 patients (11%) presented in shock secondary to the rapid onset of cardiac tamponade.
  
• This patient had mild chest and abdominal pain for only 3 days before the onset of tamponade and died despite appropriate treatment.

In patients with amebic pericarditis,

• Adams and MacLeod recommended the use of effective tissue amebicides and adequate drainage of the pericardial sac by needle aspiration.
  
• In a liver abscess of considerable size, they also recommended that it should be aspirated and that both procedures should be repeated in a patient who did not improve.
  
• In patients with subsequent constrictive pericarditis, they advised conservative management.
  
• In their experience, most of these patients improved without progression to fibrous constriction and did not require surgical intervention.

Other Complications

Other problems reported to occur in patients with an amebic liver abscess include

• secondary infection,
  
• bacteremia,
  
• hepatic failure,
  
• hemobilia, and
  
• brain abscess.
• Secondary bacterial infection is uncommon.
  
• Thus, bacteremia occurs infrequently in patients with amebic hepatic abscesses.
  
• Actually, most authors do not even list septicemia among their complications.
  
• Balasegaram reported, however, that bacteremia occurred in 7 of 371 patients (2.2%).

Even though many hepatic abscesses achieve considerable size, hepatic failure is an uncommon complication. Balasegaram reported liver failure in only 10 patients (3.1%).

Hemobilia as the result of an amebic liver abscess is rare.

• Balasegaram reported hemobilia in 2 of his patients (0.7%) and recommended hepatic resection for this complication.
  
• Koshy and associates also successfully performed a hepatic lobectomy in a single patient with hemobilia secondary to amebic abscess.
  
• Adams and MacLeod reported only 1 case of hemobilia in their 2,074 patients.
  

• Metastatic amebic brain abscess is also rare, and this is fortunate because
  
  reported cases have uniformly been fatal.

Treatment

Treatment options in patients with uncomplicated amebic liver abscess include

• amebicidal drugs,
  
• closed aspiration,
  
• percutaneous drainage, and
  
• surgical drainage.
  

Although investigators agree that all patients should be treated with amebicidal drugs, some controversy persists with regard to the choice of medication and the need for aspiration or surgical drainage.

Amebicidal Drugs

• For many years, emetine was the only effective drug available for the treatment of amebic hepatic abscess.
  
• Unfortunately, emetine and dehydroemetine are cardiotoxic and therefore must be used with great caution and must be avoided in patients with established heart disease.
  
• The next amebicidal agent effective against extraintestinal amebiasis to be introduced was chloroquine, which became available in 1948.
  
• For the next 20 years, treatment of an amebic hepatic abscess consisted of emetine or chloroquine, or both.
  
• Chloroquine had the advantages of low toxicity and oral administration.
  
• However, although the initial response with either emetine or chloroquine is excellent, the relapse rate of patients treated with chloroquine is also significantly higher.
  
• The combination of lower doses of emetine and chloroquine has also been recommended and has a cure rate of 90 to 100%, with fewer toxic reactions than seen with emetine alone.
• However, neither emetine nor chloroquine clears intestinal amebae.
  
• Therefore, these regimens should include an intestinal amebicide such as iodoquinol (a halogenated hydroxyquinolone), diloxanide furoate (an amide), carbarsone (an arsenical), or tetracycline (an antibiotic).

In 1966, Powell and colleagues introduced metronidazole (Flagyl).

• In 1969, these investigators reported 100% cure in 100 patients with doses varying from 400 mg three times a day for 5 days to 2.4 g as a single dose.
  
• These initial reports suggested that metronidazole has the advantage of being highly effective against intestinal amebiasis.
  
• However, subsequent studies demonstrated that metronidazole is not effective in all cases.

Closed Aspiration

Considerable controversy exists regarding the role of closed needle aspiration in the management of patients with amebic hepatic abscess.

• Some experts suggest that needle aspiration is rarely necessary.
  
• However, many authors list several indications for aspiration, including
  
• (1) persistence of symptoms despite adequate medical management,
  
• (2) concern regarding rupture because of the size or location of the abscess,
  
• (3) suspicion that the abscess may be pyogenic or secondarily infected with bacteria, and
  
• (4) the presence of a large abscess in which a previous aspiration has yielded more than 250 ml of pus.
  
• With the advent of ultrasound- and CT-guided aspiration, this procedure can be done safely.
  
• Even with radiologic guidance, however, the approaches to aspiration described by Ochsner and DeBakey should be used.

Clinicians who argue against routine aspiration quote the work of Sheehy and associates, who found that resolution time was unchanged by therapeutic aspiration.

• They also pointed out that aspiration increases the risk of bacterial superinfection.
  
• Clinicians who favor aspiration claim that the advantages of preventing rupture and relieving pain outweigh the low incidence of superinfection.
  
• They also point out that the clinical presentation and radiographic findings of a pyogenic abscess and those of an amebic abscess may be similar.
  
• However, now that rapid, reliable serologic tests are available, this differentiation can usually be made without the need for aspiration.
  
• The most definitive data on this subject come from the 1992 randomized trial by Van Allan and associates. These authors randomized 41 patients to amebicidal therapy alone or amebicidal therapy and percutaneous aspiration. No statistically significant benefit was demonstrated in the aspiration-treated group.
  
• As a result, aspiration should probably be reserved for
  
• large abscesses—especially those on the left,
  
• which may rupture into the pericardium—
• and for patients who do not respond to conventional therapy.

Percutaneous Drainage

Although percutaneous catheter drainage of selected cases of pyogenic hepatic abscess is reported with increased frequency, the application of this technique to patients with amebic abscess has not gained widespread popularity.

• The reasons that percutaneous catheter drainage has not become popular include fear of bacterial superinfection and the finding that most patients respond to amebicidal therapy with or without closed needle aspiration.

Surgical Drainage

Because most patients with an amebic liver abscess respond to amebicidal drug therapy with or without closed needle aspiration, open surgical drainage generally has been reserved for patients with complications.

• Most experts have avoided surgical drainage because of concerns regarding secondary bacterial invasion and the morbidity involved with a chronically draining sinus tract.
  
• General agreement exists, however, that surgical drainage is indicated in patients with rupture into the peritoneal cavity.
  
• In contrast, no clear consensus exists regarding the need for surgical drainage in patients whose abscesses have ruptured into the pleura, lung, or pericardium.
  
• In fact, Adams and MacLeod, who had the largest experience and reported the best results in patients with amebic pericarditis, did not recommend surgical drainage but preferred needle aspiration of both the pericardium and the liver abscess.

Considerable variation exists among reported series in the percentage of patients requiring open surgical drainage.

• Differences of opinion regarding the indications for surgical drainage certainly explain some of this variation.
  
• Cohen and Reynolds, for example, did not use surgical drainage in any of their 66 patients managed at the University of Southern California.
  
• Crane and associates, in a report from Korea, reported the need for open surgical drainage in 26% of their patients.
  
• In comparison, Conter and associates from southern California performed open surgical drainage in 15% of their patients.
  
• However, the largest experience with surgical drainage for amebic hepatic abscess comes from Malaysia, where Balasegaram reported that he operated on 85% of 317 patients.

Another large experience with surgical treatment of amebic liver abscess was reported from India by Eggleston and colleagues.

These authors' indications for surgery included

• (1) rupture or impending rupture,
  
• (2) failure to respond to medical therapy, and
  
• (3) inadequacy of aspiration of the left lobe.

Results of Treatment

The mortality rates for patients with amebic hepatic abscess treated between 1950 and the present vary from 0 to 34%.

• Ochsner and DeBakey in the 1930s (72% for pyogenic abscess and 16% for amebic abscess) demonstrates that amebic abscesses always have been associated with a better prognosis, and mortality has improved in both categories of liver abscesses.

Analysis of results of various series does not resolve the controversy regarding the best form of treatment for amebic liver abscess.

• Cohen and Reynolds reported only 2 deaths among 66 patients (3%) managed almost exclusively with amebicidal drugs.
• Only 4 of their patients underwent needle aspiration, and none underwent surgical intervention.
  
• Adams and MacLeod, in contrast, used closed needle aspiration in two thirds of their 2,074 patients and reported a mortality of only 2%.
  
• Ribaudo and Ochsner and Balasegaram were advocates of surgical drainage and used open surgical drainage in 71 and 100% of their patients, respectively. Of the 334 surgically managed patients in these series, only 6 (2%) died.

Among the factors associated with a poor prognosis in amebic hepatic abscess are

• jaundice,
  
• advanced age,
  
• and a major complication such as rupture into the peritoneum or pericardium.
  

Jaundice may result from compression or destruction of main intrahepatic biliary channels.

• Jaundiced patients are also more likely to have an abscess rupture into the peritoneal or pleural cavity.
  
• The report of Adams and McLeod clearly pointed out the effect of a complication on the outcome of treatment.
  
• Only 13 of 1,859 patients with uncomplicated cases (0.7%) died, whereas 26 of their 215 patients (12%) with a major complication died.
  

The presence of jaundice, advanced age, or a major complication is associated with increased risk.

• This finding is true for both amebic abscesses and pyogenic abscesses.
  
• Similarly, in both types of abscesses, late presentation may lead also to a situation that is not reversible even if the diagnosis has been established rapidly.
  
• Several large series demonstrated that excellent results can be achieved in patients with an amebic abscess.
  
• However, these reports generally came from tropical or semitropical countries where this problem is seen frequently.