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Key Clinical Questions

  • image How is spontaneous bacterial peritonitis diagnosed?

  • image What is the optimal duration of treatment of spontaneous bacterial peritonitis?

  • image How is secondary peritonitis diagnosed and treated?

  • image When should tuberculous peritonitis be suspected?

  • image How are intra-abdominal abscesses diagnosed and treated?

Peritonitis and intra-abdominal abscesses are much feared because of the high frequency of associated septic shock and multisystem organ failure. Both primary and secondary peritonitis have an in-hospital mortality rate of approximately 20%. Intra-abdominal infections are the second leading cause of infectious death in the intensive care unit. Although the precise incidence of peritonitis is unknown, it is encountered with some regularity by physicians caring for inpatients. Spontaneous bacterial peritonitis (SBP), or primary peritonitis, occurs in up to 30% of all patients with liver cirrhosis and ascites. Secondary peritonitis and intra-abdominal abscesses are important complications of common conditions on general medical wards, such as diverticulitis, peptic ulcer disease, pancreatitis, and cholecystitis. Classic symptoms and signs of intra-abdominal infection may be blunted in older or immunosuppressed patients, increasing the challenge for clinicians.


Peritonitis is inflammation of the peritoneal surface, caused by microorganisms or irritants such as foreign bodies, bile, and barium. Peritonitis is classified as primary (or spontaneous), secondary, or tertiary. In primary peritonitis, there is inflammation of the peritoneal surface without another intra-abdominal process. Secondary peritonitis develops as a result of inflammation of another structure within the abdomen. Tertiary peritonitis refers to persistent inflammation after treatment for secondary peritonitis.


Primary peritonitis, or spontaneous bacterial peritonitis (SBP), is most commonly seen in cirrhotic patients with ascites, and less often in patients with ascites from other causes, such as heart failure or systemic lupus erythematosus. Bacteria may gain access to the peritoneal fluid from hematogenous or lymphogenous spread, traversing the intact intestinal wall from the gut lumen, or by passing through the fallopian tubes from the vagina in women.


The classic signs and symptoms of peritonitis are fever, abdominal pain, and rebound tenderness. These may be mild or completely absent in cirrhotic patients. Spontaneous bacterial peritonitis should be suspected in all cirrhotic patients with clinical decompensation, such as the development of hepatic encephalopathy or hepatorenal syndrome.


Most episodes of SBP are caused by enteric Gram-negative rods, such as Escherichia coli and Klebsiella species. An important minority are caused by Gram-positive organisms, especially Streptococcus pneumoniae. Infections are rarely polymicrobial, and generally do not involve anaerobic bacteria. Table 191-1 shows the relative frequencies of common organisms isolated from ascitic fluid in patients with SBP.

TABLE 191-1Microbiology of Spontaneous Bacterial Peritonitis

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