He has been diagnosed with microscopic colitis and lymphocytic colitis.
Here are some URLs http://www.medicinenet.com/lymphocytic_colitis/article.htm
http://www.gastro.net.au/diseases/microscopiccolitis.html
http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/Collagenous_colitis