Peritonitis is inflammation within the peritoneal cavity. This chapter considers infectious causes of peritonitis. Two major types include: (1) primary (spontaneous or idiopathic) and (2) secondary. When signs of peritonitis and sepsis persist or recur after treatment for secondary peritonitis, the clinical entity has been termed tertiary peritonitis. In comparison with patients with other forms of peritonitis, tertiary peritonitis has significantly longer intensive care unit (ICU) and hospital stays, higher organ dysfunction scores, and higher mortality rates (50% to 70%).

Intraperitoneal abscesses can result from (1) localization of the initially diffuse peritoneal inflammatory response to one or more dependent sites (i.e., the pelvis, the right or left subphrenic spaces, which are separated by the falciform ligament, and Morrison’s pouch, which is the most posterior superior portion of the subhepatic space and is the lowest part of the paravertebral groove when the patient is recumbent) or (2) at the site of the intra-abdominal source of the infection (e.g., periappendiceal, pericholecystic, or peridiverticular abscess). For management of peritoneal catheter-related peritonitis, see Chapter 96, Dialysis-related infection.

PRIMARY PERITONITIS

Primary peritonitis, also called spontaneous bacterial peritonitis (SBP), is defined as infection within the peritoneal cavity without an evident intra-abdominal source. Primary peritonitis occurs at all ages: in children, in association with postnecrotic cirrhosis and with nephrotic syndrome, and in adults, with ascites from any cause, but most commonly alcoholic cirrhosis. Rarely, primary peritonitis occurs with no apparent underlying disease.