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Has he had x-rays taken of his abdomen? Do you have copies that I can look at?
I'm confused by the fat near his anus and what that means.
Does he ever vomit?
It kind of sounds like he may have a perineal hernia or some type of diverticulum of his rectum. I would do a barium contrast enema and then shoot x-rays. If there is pocketing of the rectum or colon, then that confirms a hernia. In that case, surgery can be curative.
If there is a pocketing or diverticulum of the colon or rectum, there are procedures to remove that section of bowel and allow normal defecation.
I don't think this has to be a permanent issue. I think there are more diagnostics needed to determine what exactly is going on and then go after a surgical cure. The fat glob thing is something I haven't heard before, so that's why I think additional imaging is needed to get a definitive diagnosis.
If you can get copies of the x-rays, I'd be happy to look at them and give you a second opinion. You can attach digital images on this thread.