Systematic review: acute colonic pseudo-obstruction

Acute colonic pseudo-obstruction in postchemotherapy complication of brain tumor treated with neostigmine

Acute colonic pseudo-obstruction is characterized by dilatation of the large bowel without mechanical obstruction. Although the first step of the treatment is conservative management, mechanical decompression should be performed when symptoms persist. Recently, the efficacy of pharmacologic treatment has been reported in adults, but no such data have yet been reported in children for treatment of acute colonic pseudo-obstruction resulting from chemotherapy. We report a 9-year-old boy with acute colonic pseudo-obstruction caused by chemotherapy for brain tumor who did not respond to initial supportive therapy, but who was successfully treated with neostigmine.

Acute colonic pseudo-obstruction

Acute colonic pseudo-obstruction (ACPO) is a syndrome of massive dilation of the colon without mechanical obstruction that develops in hospitalized patients with serious underlying medical and surgical conditions. Increasing age, cecal diameter, delay in decompression, and status of the bowel significantly influence mortality, which is approximately 40% when ischemia or perforation is present. Evaluation of the markedly distended colon involves excluding mechanical obstruction and other causes of toxic megacolon such as Clostridium difficile infection and assessing for signs of ischemia and perforation. The risk of colonic perforation in ACPO increases when cecal diameter exceeds 12 cm and when the distention has been present for greater than 6 days. Appropriate management includes supportive therapy and selective use of neostigmine and colonoscopy for decompression. Early recognition and management are critical in minimizing complications.

Serotonin and its role in colonic function and in gastrointestinal disorders

Serotonin (5-HT) is most commonly thought of as a neurotransmitter in the central nervous system. However, the predominant site of serotonin synthesis, storage, and release is the enterochromaffin cells of the intestinal mucosa. Within the intestinal mucosa, serotonin released from EC cells activates neural reflexes associated with intestinal secretion, motility, and sensation. Two important receptors for serotonin that are located in the neural circuitry of the intestines are the 5-HT(3) and 5-HT(4) receptors; these are the targets of drugs designed to treat gastrointestinal disorders. 5-HT(3) receptor antagonists are used to treat nausea and emesis associated with chemotherapy and for functional disorders associated with diarrhea. 5-HT(4) receptor agonists are used as promotility agents to promote gastric emptying and to alleviate constipation. Because of the importance of serotonin in normal gut function and sensation, a number of studies have investigated potential changes in mucosal serotonin signaling in pathologic conditions. Despite the inconsistencies in the current literature, changes in serotonin signaling have now been demonstrated in inflammatory bowel disease, irritable bowel syndrome, postinfectious irritable bowel syndrome, and idiopathic constipation. Emerging evidence has led to many contradictory theories regarding serotonin signaling and its roles in the pathology of gut disorders. This review summarizes the current medications affecting serotonin signaling and provides an overview of our current knowledge of the changes in serotonin that occur in pathologic conditions.