He was rediagnosed with IBS, Irritated Bowel Syndrome. Just today on my way to school, NPR did a story on how a certain antibiotic helped patients with IBS.
http://www.npr.org/2011/01/06/132699336/Antibiotics-Shown-To-Help-Irritable-Bowel-Syndrome
http://www.npr.org/2011/01/06/132699336/Antibiotics-Shown-To-Help-Irritable-Bowel-Syndrome