Spontaneous bacterial peritonitis (SBP) is the development of a bacterial infection in the peritoneum, despite the absence of an obvious source for the infection. It is specifically an infection of the ascitic fluid – an increased volume of peritoneal fluid. Ascites is most commonly a complication of cirrhosis of the liver. SBP has a high mortality rate.
The diagnosis of SBP requires paracentesis, a sampling of the peritoneal fluid taken from the peritoneal cavity. If the fluid contains large numbers of white blood cells known as neutrophils (>250 cells/μL), infection is confirmed and antibiotics will be given, without waiting for culture results. In addition to antibiotics, infusions of albumin are usually administered. 30% of SBP patients develop kidney malfunction, one of the strongest predictors for mortality. Where there are signs of this development albumin infusion will also be given.
Signs and symptoms
Signs and symptoms of spontaneous bacterial peritonitis (SBP) include fevers, chills, nausea, vomiting, abdominal pain and tenderness, general malaise, altered mental status, and worsening ascites. The percentage of gram-positive bacteria responsible has been increasing. Bacterial translocation is thought to be the key mechanism for the development of SBP. Small intestinal bacterial overgrowth which may be implicated in this translocation, is found in a large percentage of those with cirrhosis.
With respect to compromised host defenses, patients with severe acute or chronic liver disease are often deficient in complement and may also have malfunctioning of the neutrophilic and reticuloendothelial systems.
As for the significance of ascitic fluid proteins, it was demonstrated that cirrhotic patients with ascitic protein concentrations below 1 g/dL were 10 times more likely to develop SBP than individuals with higher concentrations. It is thought that the antibacterial, or opsonic, activity of ascitic fluid is closely correlated with the protein concentration. Additional studies have confirmed the validity of the ascitic fluid protein concentration as the best predictor of the first episode of SBP.
Diagnosis
Infection of the peritoneum causes an inflammatory reaction with a subsequent increase in the number of neutrophils in the fluid.
The fluid is also cultured to identify bacteria. If the sample is sent in a plain sterile container, 40% of samples will identify an organism, while if the sample is sent in a bottle with culture medium, the sensitivity increases to 72–90%.
- Previous SBP
People with cirrhosis admitted to the hospital should receive prophylactic antibiotics if:
- They have bleeding esophageal varices
Studies on the use of rifaximin in cirrhotic patients, have suggested that its use may be effective in preventing spontaneous bacterial peritonitis.
Treatment
Antibiotics
Although there is no high-quality evidence, the third-generation cephalosporins are considered the standard empirical treatment for spontaneous bacterial peritonitis in people with cirrhosis.
Other resources mentioned that empiric third-generation cephalosporins are recommended for suspected SBP with a Polymorphonuclear neutrophils (PMN) count over 250 cells/μL. The exception was that if in cases of prior beta-lactam use or hospital-acquired infections, the treatment should be guided by susceptibility testing. Patients with a PMN count above 500 cells/μL require hospitalization and antibiotics, with follow-up ascitic fluid analysis. Lack of improvement within 48 hours may indicate secondary bacterial peritonitis, potentially requiring surgery. A PMN reduction of at least 25% suggests an adequate response to treatment.
In practice, cefotaxime is the agent of choice for treatment of SBP. After confirmation of SBP, hospital admission is usually advised for observation and intravenous antibiotic therapy.
Where there is a risk of kidney malfunction developing in a syndrome called hepatorenal syndrome, intravenous albumin is usually administered too. Paracentesis may be repeated after 48 hours to ensure control of infection. After recovery from a single episode of SBP, indefinite prophylactic antibiotics are recommended.
Intravenous albumin
A randomized controlled trial found that intravenous albumin on the day of admission and on hospital day 3 can reduce kidney impairment.
Prognosis
With proper treatment, infection-related mortality in SBP is low, but outcomes worsen if sepsis develops. In hospitals, non-infection-related mortality can reach 20–40%, while one- and two-year mortality rates are approximately 70% and 80%, respectively.
Complications
There are complications associated with SBP such as:
- Renal failure
- Sepsis
- Liver failure/insufficiency
- Tense ascites
- Bleeding after paracentesis
- Bowel perforation after paracentesis
- Spontaneous fungal peritonitis.
History
SBP was first described in 1964 by Harold O. Conn.