Rectal obstruction by a giant pharmacobezoar composed of magnesium oxide: report of a case.

This report presents the rare case of a 75-year-old woman who developed a rectal obstruction caused by a pharmacobezoar, following the long-term ingestion of magnesium oxide cathartics for constipation. She was admitted to the hospital with lower abdominal pain and nausea. Abdominal computed tomography and magnetic resonance imaging showed that a huge calcified mass caused the rectal obstruction. A divided sigmoid colostomy was performed to relieve her symptoms, a colonoscopy from the distal stoma delineated a huge bezoar in the rectum, and thereafter she underwent an enterotomy. Magnesium oxide was detected in an analysis of a sample from this bezoar. Phamacobezoars resulting from laxatives or cathartics have rarely been reported. The current report showed a rectal obstruction caused by a pharmacobezoar composed primarily of magnesium oxide.