Inclusion Criteria:  Age > 18yrs Major abdominopelvic surgery with colon or rectal resection Preoperative diagnosis of Crohn's disease, ulcerative colitis, indeterminate colitis Elective surgery candidate for standard of care VTE prophylaxis  Exclusion Criteria:  age < 100 yrs aspirin allergy loop ileostomy closure emergency surgery peptic ulcer disease cirrhosis bleeding or clotting disorder thrombocytopenia chronic renal insufficiency or failure severe anemia < 7 preoperatively need for therapeutic anticoagulation or anti-platelet agents post-operatively including aspirin, warfarin, heparin, clopidogrel, rivaroxaban, others