abdominal perforation fistula gastrointestinal abscess intra history months prior ulcer 
abdominal diverticulitis abscess carcinomatosis obstruction intra gi coming gastrointestinal acute 
perforation gastrointestinal history fistula fistulae months ulceration bleeding gi prior 
abdominal including dose treatment disorders fistula study filter abscess ischemic 
abdominal bowel obstruction perforation abscess intra diverticulitis gastrointestinal carcinomatosis factors