Gas in any space, including the GI tract, will expand as you ascend/decompress. For the most part, this is not an issue, because if it was already there at surface, it contracted as you descended, and would be the same volume when you returned to surface. If, however, you swallowed air at 3 ATM, the volume would be increased three fold at surface, and that could cause problems. An actual stomach rupture was described at a course I once took, and I'll try to dig out the reference. Circumstances were unusual--an attempted body recovery in a dangerous cave at roughly 100 FSW, entrapment, OOA, last second rescue, and probably air swallowing at that point. Severe abd pain on ascent with eventual diagnosis of stomach rupture.
It would seem highly unlikely that there would be enough new gas produced during a dive to cause problems before it could be elminated. Gas is produced only in the large intestine, which can accomodate a lot of expansion.
As for the drysuit, Atticus, was there any fish mortality after you vented? Our club's chili cook-off is next month, but we usually eat after diving. Just in case, it's probably good advice to stay upwind of the drysuits when we unzip.
