Bacterial Peritonitis

Also Know As Spontaneous Bacterial Peritonitis

Bacterial Peritonitis

Spontaneous bacterial peritonitis (SBP) is bacterial infection of the fluid found within the peritoneal cavity, or ascetic fluid.  This occurs acutely and is usually associated with patients undergoing peritoneal dialysis due to contamination of the dialysate fluid.  Other populations at risk of developing spontaneous bacterial peritonitis include those with cirrhosis, nephrosis, and congestive heart failure.

Pathophysiology

It has been thought that spontaneous bacterial peritonitis develops through the mechanism called bacterial translocation.  Bacterial organisms found within the lumen of the intestine migrates transmurally, resulting to an infection of the ascitic fluid.  Another possible mechanism is that the source of the infecting organism comes from the blood, and combined with an impaired immune system, may lead to this condition.

Seventy-five percent of the pathogens causing spontaneous bacterial peritonitis are aerobic gram-negative organisms such as Escherichia coli.  The remaining causative organisms include aerobic gram-positive bacteria (eg, streptococci, Enterobateriaceae).  Approximately 92% of the cases are able to isolate a single organism, while 8% are caused by a mix of several bacteria (polymicrobial)

Patients who are highly predisposed to developing spontaneous bacterial peritonitis are those who are in a decompensated state with their liver cirrhosis.  Patients with low protein levels in the ascitic fluid also have a higher risk.

Epidemiology

Among patients with ascites, the prevalence rate may reach up to 18%.  The mortality rate ranges from 40-70% in adults with cirrhosis while it is lower in children with nephrosis.

Clinical Features

As many as 30% of cases of spontaneous bacterial peritonitis have no presenting symptoms.  The most common symptoms include fever and chills, abdominal pain or discomfort, worsening encephalopathy, diarrhea, ileus, and worsening ascities or renal failure.  In these patients, they usually have abdominal tenderness, have low blood pressure, and have signs of liver failure. 

Diagnosis

A very important test is the peritoneal fluid analysis.  The ascitic fluid is examined for its cell and differential counts, culture studies, cytology, lactate and pH levels.  The ascitic fluid can be obtained through a procedure called paracentesis.   

Radiographs of the chest and abdomen may be taken if a perforated bowel is being considered.  Ultrasonography can confirm the presence of ascitic fluid and guide paracentesis.

Treatment

Antibiotics are initiated immediately in order to reduce morbidity and prevent complications.  The most commonly used regimen is the combination of an aminoglycoside and ampicillin, which provides empiric coverage.  Third generation cephalosporins are equally as effective and reduces the risk of nephrotoxicity or problems to the kidneys.  Antibiotics are usually given for 10 to 14 days.

Public Discussion