Karen L. Krok; Andrés Cárdenas


Semin Respir Crit Care Med. 2012;33(1):3-10. 

In This Article

Spontaneous Bacterial Empyema

A spontaneous bacterial empyema (SBEM) is an infection of a preexisting hydrothorax in which pneumonia has been excluded. However, this term may be confusing because there is typically no evidence of pus or abscess in the thoracic cavity; for this reason, some authors have proposed that it be called spontaneous bacterial pleuritis.[32] However, this name has not gained acceptance, and most published studies referring to infections of the pleural fluid in cirrhotics use the term SBEM.

Infection of the pleural fluid must be considered in any patient with hydrothorax who develops fever, pleuritic pain, encephalopathy, or unexplained deterioration in renal function. Therefore a high index of suspicion is essential for its diagnosis. In the evaluation of a hepatic hydrothorax, a thoracentesis should be performed, and a cell count from that fluid should always be sent. The diagnostic criteria for SBEM are as follows:

  • Positive pleural fluid culture and a polymorphonuclear count greater than 250 cells/mm3

  • Negative pleural fluid culture and a polymorphonuclear count greater than 500 cells/mm3

  • No evidence of pneumonia on a chest x-ray

Fluid should be inoculated at the bedside directly into a blood culture bottle. This increases the sensitivity for the diagnosis of SBEM from 33 to 77%.[33]

The incidence of SBEM is similar to the reported incidence of spontaneous bacterial peritonitis (SBP); 15 to 20% of hospitalized patients with cirrhosis will have SBP, and in a prospective study Xiol and colleagues found a 13% incidence of SBEM.[33–36] Interestingly up to 40% of cases of SBEM are not associated with SBP.[33] Some patients will not have ascites, supporting the hypothesis that enteric microorganisms reach the pleural space through bacteremia as has been reported in SBP.[37] This is in addition to direct spread of the infection from the peritoneal space through the diaphragmatic defects. Because SBEM can develop without simultaneous SBP, a thoracentesis should be performed in a patient with a clinical suspicion for an infection even if a paracentesis has not revealed an infection. The most frequent bacteria involved are Enterobacteriaceae (Escherichia coli and Klebsiella pneumonia), Streptococcus species and Enterococcus species. Not surprisingly, these are also the most common bacterial causes of SBP.

Treatment for SBEM typically involves the use of a third-generation cephalosporin. The use of albumin in preventing hepatorenal syndrome is the standard of care in patients with SBP but it has not been studied in patients with SBEM.[38] These patients should be placed on life-long (or until a liver transplant) prophylaxis for the prevention of SBEM or SBP with norfloxacin, ciprofloxacin, or bactrim.

Chest tube insertion is not indicated in the management of SBEM unless frank pus is present. Chest tube insertion can lead to renal insufficiency, prolonged drainage through the insertion site following removal, increased risk of secondary infection, and further protein loss.[39,40] This will be further discussed in the treatment section of this article.

A few studies have evaluated the risk factors for developing SBEM. Sese and colleagues found that a low pleural fluid total protein (less than 1.0 mg/dL) and low C3 levels as well as a higher Child-Pugh Score were associated with the development of an SBEM.[30] Simultaneous SBP is also a risk factor.[5] Mortality is as high as 20% in patients with SBEM.[33,41] Just as the development of SBP is an indication for a liver transplant evaluation, the development of SBEM should prompt a referral to a liver transplant center.