Spontaneous Bacterial Empyema - An Overview

Introduction

Spontaneous bacterial empyema refers to the accidental infection of the pleural fluid (accumulation of fluid between the pleural membrane and the lining of the chest cavity) associated with liver abnormalities such as hepatic hydrothorax or liver cirrhosis but in the absence of pneumonia. It is also called spontaneous bacterial pleuritis. Spontaneous bacterial empyema also occurs as a complication of hepatic hydrothorax, presenting with different clinical courses, pathogenesis, and treatment approaches from empyema, which occurs secondary to pneumonia. It is associated with a high rate of morbidity and mortality. This condition is usually underdiagnosed. The incidence of spontaneous bacterial empyema in hepatic hydrothorax is 13 to 16 percent and in patients with cirrhosis is about 2 to 2.4 percent.

What Signs and Symptoms Are Associated With Spontaneous Bacterial Empyema?

Various signs and symptoms of spontaneous bacterial empyema include:

• Chest pain.

• Dyspnea (shortness of breath).

• Epigastric abdominal pain.

• Acute encephalopathy (a disease that causes brain damage).

• Non-radiating right-sided chest pain.

• Tachycardia (rapid heartbeat).

What Causes Spontaneous Bacterial Empyema?

The primary causative organism is Enterobacteriaceae (Escherichia coli and Klebsiella pneumoniae) are isolated from the spontaneous bacterial empyema patients.

What Is the Pathogenesis of Spontaneous Bacterial Empyema?

• The pathogenesis of spontaneous bacterial empyema is unclear.

• It occurs due to direct bacterial spread from the peritoneal cavity.

• The report suggests that 40 percent of spontaneous bacterial empyema is not associated with spontaneous bacterial peritonitis (an acute bacterial infection of the abdominal or ascitic fluid).

• This may occur in the absence of ascites (build-up of fluid in the abdomen). In such cases, transient bacteremia, which infects the pleural space, can be the underlying pathogenic mechanism.

• Since patients who develop spontaneous bacterial peritonitis have reduced ascites complement levels and ascitic fluid opsonic cavity (the defense mechanism involved in the dilution of antimicrobial proteins of ascitic fluid), which reflects the importance of local factors in the prevention of the colonization of ascitic fluid by pathogenic bacteria. Similarly, defective local pleural factors are considered to enhance infection in these patients.

• The impaired opsonic activity of pleural fluid has improved bacterial translocation. In patients with spontaneous bacterial empyema, low complement component (C3) levels can be seen in addition to the lower pleural fluid opsonic cavity.

What Are the Risk Factors for Spontaneous Bacterial Empyema?

Certain factors associated with the development of spontaneous bacterial empyema include:

• High Child-Pugh score (a score used to determine the prognosis of chronic liver disease).

• Low level of serum albumin.

• Low pleural fluid protein.

• Concomitant spontaneous bacterial peritonitis.

• Low pleural fluid complement component (C3) levels.

What Is Hepatic Hydrothorax?

• Hepatic hydrothorax is the pleural effusion in cirrhotic patients, usually more significant than 500 milliliters, without underlying cardiac or pulmonary diseases.

• It is a rare complication of portal hypertension with a five to 12 percent prevalence in patients with liver cirrhosis.

• It is usually right-sided in 65 to 87 percent of cases but may present with bilateral or left-sided.

What Are the Investigatory Approaches to Spontaneous Bacterial Empyema?

• Chest X-ray: There is no evidence of pneumonia in the chest radiography.

• Pleural Fluid Culture: The culture report shows positive results with a polymorphonuclear cell count greater than 250 cells per millimeter. The pleural fluid study includes polymorphonuclear leukocyte count, biochemical analysis, and fluid culture performed by conventional and modified methods. The modified fluid culture technique is performed by injecting 10 milliliters of pleural fluid into a blood culture bottle at the bedside since it consists of an opsonin inhibitor that protects bacteria from complement -or phagocyte-mediated killing. However, the pleural fluid analysis reveals limited efficacy in the diagnosis of spontaneous bacterial empyema since lactate dehydrogenase, glucose, and total protein are not reported to differ significantly between the patients with spontaneous bacterial empyema and those with noninfected infusion, and the value did not correlate with the polymorphonuclear cell count.

• Computed Tomography (CT): Computed tomography reveals a large right-sided pleural effusion with no evidence of pneumonia.

• Thoracentesis: It is the most accurate and effective method of diagnosing spontaneous bacterial empyema. The findings reveal a transudate with an increased white blood cell count and polymorphonuclear leukocyte levels. The pleural fluid culture shows the later growth of pan-sensitive Escherichia coli. It is indicated in patients presenting with symptoms such as pleuritic chest pain, encephalopathy, fever, and reduced renal function.

What Are the Diagnostic Criteria for Spontaneous Bacterial Empyema?

The following are the specific criteria evaluated for diagnosing spontaneous bacterial empyema:

• Polymorphonuclear leukocyte count greater than 500 per millimeter cube or positive fluid culture with polymorphonuclear cell count greater than 250 cells per millimeter cube.

• Absence of pneumonia or infection process on chest radiography.

• Serum or pleural fluid albumin gradient greater than 0.04 oz per deciliter.

How To Manage Spontaneous Bacterial Empyema?

• The first line of treatment includes antibiotic treatment with the empirical use of third-generation Cephalosporins.

• Initially, the treatment starts with the intravenous administration of third-generation Cephalosporin - Ceftriaxone 0.04 oz daily for seven to ten days.

• An intravenous administration of albumin is also recommended.

• A chest tube placement is not advisable as it may result in life-threatening fluid depletion, electrolyte imbalance, and protein loss.

• Empirical antibiotic therapy is managed along with the management of underlying cirrhosis and hepatic hydrothorax.

• Patients with spontaneous bacterial empyema have an approximately 20 percent mortality rate during therapy. This is reduced with the administration of albumin infusion.

• Albumin therapy is provided with 0.05 oz per kilogram on the first day and 0.04 oz per kilogram on the third day.

• In the case of slow recovery, a repeat thoracentesis procedure is recommended to record whether the patient is responding to treatment.

• The main aim of the treatment is to relieve the symptoms and control the infections until liver transplantation is to be performed. Liver transplantation is an excellent option for patients with hepatic hydrothorax, even complicated with empyema.

Conclusion

Spontaneous bacterial empyema is a complication of patients with hydrothorax and liver cirrhosis. It is underdiagnosed due to the poorly understood pathogenesis, nonspecific symptoms, and delay in the diagnostic approach with thoracentesis. The standardization and improvement of diagnostic and therapeutic guidelines help to reduce the increased mortality and morbidity associated with spontaneous bacterial empyema.