Another source of adhesions is not at all controversial, and doesn't involve surgery, a blow to the abdomen, or an infection -- which is that a burst ovarian cyst will certainly cause adhesions. Actually the mittelschmertz theory, if you think about it, is really a theory about ovarian cysts. It says that the normally ripening ovarian follicle gets enough fluid in it that it behaves like a baby cyst.
Both of these are kind of long-shots, though. I think that an exploding cyst typically gives an adhesion pattern which looks a lot like what you would see from an infection -- in other words, like an explosion at a glue factory. Not adhesions confined to one small space. But on the other hand, no one really understands the mechanisms of adhesions, and why some people don't get them even though they have abdominal surgery. It is possible that at some point years back you had an ovarian cyst that exploded, or a PID that you didn't know you had, and by whatever mysterious process which the human body clearly has in some cases, your body "cleaned up" massive adhesions everywhere except in that one spot. And it was long enough ago that none of those cleared-out adhesions have left the slightest sign.
Adhesions are mysterious in many ways. It is estimated that about a third of all Americans have adhesions. That's 90,000,000 people. That's a HUGE number. It is very clear that the vast vast majority of those people have no problems at all. So if you have adhesions and no obvious cause, it wouldn't be the biggest adhesion mystery out there!
-- cathy :-)