I never thought my kids had any real tummy troubles. We are not the best of eaters in our family (too much fast food and snacks) and once in awhile, all of us (hubby, me, and 3 kids) would/will get looser bowel movements (not quite diarrhea). My oldest son (the one just diagnosed) has always been the worst eater in terms of a balanced diet. He has used the bathroom 3-5 a day forever but mostly normal movements.
Bratcat's illness seems to have come on suddenly. It is weird that she flared both times in September just after school started. Honestly, she has more stress at this time of the year (concerts, musical, music competition, extracurricular activities, etc) than at the beginning of the school year. Next September is already in the back of our minds.
Her older brother had the abcess. Until it got big, he never complained (never complains about anything--he is very low-key, low-maintenance). When the doctor mentioned that it looked like there were scars from previous abcesses, he said he "thinks" he had some issues down there in the past! As soon as Bratcat was diagnosed, I began asking about the usual symptoms--diarrhea, pain, blood, mucous. He said he had none of those symptoms (a small amount of blood once when he wiped, chalked it up to pushing too hard).
None of my kids were really ever sick. They usually got perfect attendance in school for years. Their younger brother has asthma that seems to be getting better. He has always been the biggest complainer of the family when he doesn't feel well. Must be a youngest child thing (I was the same). As he gets older, he doesn't complain as much about the little things.
Hope your daughter is feeling better soon.