Acute abdomen: peritonitis

Peritonitis is inflammation of the peritoneum and represents an important cause of surgical morbidity and mortality. It may be localized or generalized, and is thought to pass through three phases: firstly, a phase of rapid removal of contaminants from the peritoneal cavity into the systemic circulation; secondly, a phase of synergistic interactions between aerobes and anaerobes; and thirdly, an attempt by host defences to localize infection. Peritonitis is commonly caused by bacteria, but can be chemical (aseptic), biliary, tuberculous, chlamydial, drug-induced or induced by other, rarer causes. Bacterial peritonitis is subclassified into primary or secondary on the basis of whether or not the integrity of the gastrointestinal tract has been compromised. Typically, the patient with peritonitis complains of severe abdominal pain and may exhibit the characteristic Hippocratic facies. Abdominal palpation demonstrates tenderness, guarding and rebound tenderness. Initial laboratory investigations should include urea and electrolytes, full blood count and blood gases. An erect radiograph of the chest demonstrates pneumoperitoneum in about 70-80% of visceral perforations. CT often plays a role in confirming specific diagnoses (e.g. subphrenic abscess). Immediate management should include fluid resuscitation, high-flow oxygen, appropriate antibiotics (i.v.) and analgesia. Definitive management is surgical except for a small group of patients in whom conservative management with fluids (i.v.) and antibiotics (i.v.) is indicated. Surgical management can be via a laparotomy or, in some conditions, laparoscopy. Control of the primary site of sepsis is the main determinant of outcome. Most patients recover quickly. However, major generalized peritonitis is associated with organ dysfunction/failure, and mortality can up to 20-40% in the UK.