The best lies are half-truths. Maybe he actually has Crohns and there's enough documentation to make this story (half-)plausible.

(just offering one possible answer to this question - I don't know any facts about this case)

I think that is why evan__ suggested the heart valve defect, a genetic condition that often goes undetected until it kills you. You often hear of stories of young, athletic people dropping dead and being linked to some defect they've had since birth that went undetected.