There's definite tests for crohns though and I'm sure he would've been tested if the Doc's thought he had it.Misdiagnosis does happen. There is a lot of confusion about the differences between IBS (irritable bowel syndrome), and IBD (inflammatory bowel disease), such as Crohn's. Both can cause rectal bleeding, though. Even doctors can get confused - prescribing NSAIDs for IBD sufferers, which is a complete no-no as they can cause a flare-up.