My Dad (86) has been suffering with extreme diarrhea off and on for the last four weeks. Any advice?

When diarrhea is frequent, has no apparent cause, and becomes a chronic problem, it may signal something more serious, such as colon cancer or inflammatory bowel disease. Call the MD and get a referral to a gastroenterologist.

Time to visit the doctor. The diarrhea could be caused by many things -- medications, food sensitivities, intestinal problems, microbial infections. A physician should be able to tell what might be causing the problem. I hope he can find an effective treatment.