I've had this problem for years. I went to a rectal surgeon to see if there was a fistula in ano or anal fissure that might be causing this. I read about those as possible causes on a forum.
He told me I didn't have those but to take Florastor 2x a day AND 1 tablet of Phillips Colon Health 1x a day. They're both probiotics, I had tried others but these two seem to work much better than the others as far as getting rid of the smell. No more smell!!
The Florastor is kind of expensive, about $35 a month but he said a lot of times you just have to take it for a month or two and the bacteria continue to live in the colon and small intestine and keep the smell away. He said he hasn't seen a patient with this problem except one other time. He's probably been practicing for 20 years.
Two other things that might have cured it but I don't think so. I have been doing Kegel exercises but I was doing those for a while before I saw the rectal surgeon. I also saw an ENT thinking it might be something in my sinuses or throat causing the smell, he prescribed antibiotics (Avelox), but it didn't seem to help, saw rectal surgeon I mentioned above a week after I finished the antibiotics so it might be possible that the antibiotics did away with the smell but I remember smelling it some after I was done with the antibiotic.
If just using the probiotics doesn't work then there is an antibiotic that kills all intestinal bacteria, then afterwards you take probiotics like these to restore it. So its like starting from scratch. The downside is the antibiotic costs about 500 dollars and is not covered by insurance usually. Luckily I didn't have to take it.
I know this is an old thread but it came up first when I did a Gooogle search. Email me with any questions. I hope this helps!!