Kalpana Kalpana (Editor)

Spontaneous bacterial peritonitis

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ICD-9-CM  567.23
eMedicine  emerg/882

Spontaneous bacterial peritonitis (SBP) is the development of a bacterial infection in the peritoneum causing peritonitis, despite the absence of an obvious source for the infection. It occurs almost exclusively in people with portal hypertension (increased pressure over the portal vein), usually as a result of cirrhosis of the liver. It can also occur in patients with nephrotic syndrome.


The diagnosis of SBP requires paracentesis (aspiration of fluid with a needle) from the abdominal cavity. If the fluid contains bacteria or large numbers of neutrophil granulocytes (>250 cells/µL) (a type of white blood cells), infection is confirmed and antibiotics are required to avoid complications. In addition to antibiotics, infusions of albumin are usually administered.

Signs and symptoms

Signs and symptoms of spontaneous bacterial peritonitis include fevers, chills, nausea, vomiting, abdominal tenderness, and general malaise. Affected individuals may complain of abdominal pain and worsening ascites. Thirteen percent of patients have no signs or symptoms. Hepatic encephalopathy may be the only manifestation of SBP; in the absence of a clear precipitant for the encephalopathy, all patients should undergo paracentesis, or sampling of the ascites fluid, in order to assess for SBP.


Infection of the peritoneal fluid (ascites) with gram-negative bacteria is the most common cause of SBP. The most frequently isolated gram negative bacterial species in ascitic fluid from those with SBP are E. coli and Klebsiella. Gram-positive cocci species, such as streptococci and staphylococci, have historically been responsible for less than 25% of SBP cases though the incidence of such cases has been increasing. Anaerobic and fungal infections of the ascitic fluid are rare but have been reported with organisms such as Aeromonas, Bordetella bronchiseptica, Candida species, Salmonella paratyphi A, and Pasteurella multocida.


SBP is thought to result from a combination of factors inherent in cirrhosis and ascites, such as prolonged bacteremia secondary to compromised host defenses, intrahepatic shunting of colonized blood, and defective bactericidal activity within the ascitic fluid. Suppression of the stomach's secretion of acid, such as by proton pump inhibitor medications, has also been associated with SBP in patients with advanced cirrhosis. Contrary to earlier theories, transmucosal migration of bacteria from the gut to the ascitic fluid is no longer considered to play a major role in the etiology of SBP.

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 is made by paracentesis (needle aspiration of the ascitic fluid). SBP is diagnosed if the fluid contains neutrophils (a type of white blood cell) at greater than 250 cells per mm3 (equals a cell count of 250 x106/L) fluid in the absence of another reason for this (such as inflammation of one of the internal organs or a perforation). 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%.


All people with cirrhosis might benefit from antibiotics (oral fluoroquinolone norfloxacin) if:

  • Ascitic fluid protein <1.0 g/dL. Patients with fluid protein <15 g/L and either Child-Pugh score of at least 9 or impaired renal function may also benefit.
  • Previous SBP
  • People with cirrhosis admitted to the hospital should receive prophylactic antibiotics if:

  • They have bleeding esophageal varices
  • Antibiotics

    After confirmation of SBP, patients need hospital admission for intravenous antibiotics. They will often also receive intravenous albumin. A repeat paracentesis in 48 hours is sometimes performed to ensure control of infection. Once patients have recovered from SBP, they require regular prophylactic antibiotics as long as they still have ascites.


    The addition of a prokinetic drug to an antibiotic regime reduces the incidence of spontaneous bacterial peritonitis possibly via decreasing small intestinal bacterial overgrowth.

    Intravenous albumin

    A randomized controlled trial found that intravenous albumin on the day of admission and on hospital day 3 can reduce kidney impairment.


    Patients with ascites underwent routine paracentesis, the incidence of active SBP ranged from 10% to 27% at the time of hospital admission.


    SBP was first described in 1964 by Harold O. Conn.


    Spontaneous bacterial peritonitis Wikipedia