The peritoneum consists of a single layer of mesothelial cells that covers all intra-abdominal organs. The portion that covers the abdominal wall is derived from the underlying somatic structures and is innervated by somatic nerves. The portion covering the viscera is derived from visceral mesoderm and is innervated by nonmyelinated visceral afferents. Inflammation of the peritoneum, or peritonitis, usually is caused by infection but may result from exogenous irritants introduced by penetrating injuries or surgical procedures, radiation, and endogenous irritants such as meconium. Infectious peritonitis can be an acute complication of intestinal inflammation and perforation, as in appendicitis, or it can occur secondary to contamination of preexisting ascites associated with renal, cardiac, or hepatic disease. In this setting, when there is no other intra-abdominal source, it is referred to as spontaneous bacterial peritonitis. Spontaneous bacterial peritonitis is usually due to pneumococcus and less often to Escherichia coli.
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Peritonitis is characterized on examination by marked abdominal tenderness. Rebound tenderness also generally is quite pronounced. The patient tends to move very little owing to intense peritoneal irritation and pain. Fever is not always present, and absence of fever should not be regarded as contradictory to the diagnosis. Patients who are taking corticosteroids for an underlying condition, such as nephrotic syndrome, are likely to have little fever and reduced tenderness.
Blood tests should focus on identifying the nature of the inflammation and its underlying cause. An elevated white blood cell count, erythrocyte sedimentation rate, and C-reactive proteinsuggest infection. In children older than 5 years, appendicitis isthe leading cause. Total serum protein, albumin, and urinalysisshould be ordered to rule out nephrotic syndrome. Liver function tests should be performed to rule out chronic liver diseasecausing ascites. The best way to diagnose suspected peritonitisis to sample the peritoneal fluid with a needle or catheter (paracentesis). Peritoneal fluid in spontaneous bacterial peritonitis has a high neutrophil count of greater than 250 cells/mm3. Other tests that should be run on the peritoneal fluid includeamylase (to rule out pancreatic ascites), culture, albumin, andlactate dehydrogenase concentration. For culture, a large sampleof fluid should be placed into aerobic and anaerobic blood culture bottles immediately on obtaining the sample.
Appendicitis may be identified by ultrasound or computed tomography (CT) scan. When other intra-abdominal emergencies are suspected, such as midgut volvulus, meconium ileus, peptic disease, or any other condition predisposing to intestinal perforation, specific testing should be performed.
Peritonitis caused by an intra-abdominal surgical process, such as appendicitis or a penetrating wound, must be managed surgically. Spontaneous bacterial peritonitis should be treated with a broad-spectrum antibiotic with good coverage of resistant pneumococcus and enteric bacteria. Cefotaxime is generally effective as initial therapy while awaiting culture and sensitivity results. Anaerobic coverage with metronidazole should be added whenever a perforated viscus is suspected.
Bishop W, editor: Pediatric Practice: Gastroenterology, New York, 2010,
Feldman M, Friedman LS, Brandt LJ, editors: Gastrointestinal and Liver
Disease: Pathophysiology/Diagnosis/Management, Philadelphia, 2010,
Kleinman R, Goulet OJ, Mieli-Vergani G, et al: Walker’s Pediatric
Gastrointestinal Disease, Hamilton, Ontario, 2008, BC Decker