Differential Diagnosis for Bleeding Per Rectum Post Aortic Aneurysm Repair

• Single Most Likely Diagnosis
  • Aortoenteric fistula: This is a serious and potentially life-threatening complication that can occur after aortic aneurysm repair. It involves the formation of a fistula (an abnormal connection) between the aorta and the intestine, leading to bleeding. The proximity of the aortic graft to the intestinal structures increases the risk of this complication, especially if there was any technical difficulty during the surgery or if the patient has an infection.
• Other Likely Diagnoses
  • Ischemic colitis: This condition occurs when there is an interruption or reduction in the blood flow to the colon, which can happen during or after aortic aneurysm repair due to the manipulation of major blood vessels. Ischemic colitis can cause bleeding, among other symptoms, and is a plausible cause in this scenario.
• Do Not Miss Diagnoses
  • Graft infection: Although less common, an infection of the aortic graft can lead to severe complications, including erosion into adjacent structures and subsequent bleeding. Early detection is crucial for managing this condition effectively.
  • Suture line bleeding: Bleeding from the suture lines of the anastomosis (the connection made between the aorta and the graft) is a potential complication that needs to be considered, especially in the early postoperative period.
• Rare Diagnoses
  • Colonic ulceration: Ulcers in the colon can cause bleeding and, while less directly related to aortic aneurysm repair, could be considered in the differential diagnosis, especially if the patient has a history of colonic disease or is on medications that could increase the risk of ulceration.
  • Angiodysplasia: This is a condition characterized by the presence of abnormal blood vessels in the colon that can bleed. It is a rare cause of gastrointestinal bleeding and would be an unusual cause in the context of post-aortic aneurysm repair but should be considered if other causes are ruled out.