Patients undergoing surgery on their Aorta can get ischemia, a lack of blood flow, to their intestines and colon. This is very serious, as 2 out of 3 patients who have this problem die before leaving the hospital. A device developed by Spectros, called T-Stat, is approved by the US FDA to detect ischemia, and has been reported to detect ischemia in AAA aneurysm surgery and stenting, allowing the surgeon or interventional radiologist to take action quickly, while the colon ischemia is still treatable.

This purpose of this study is to establish how T-Stat can best be used to prevent deaths.

Inclusion Criteria:

• Aortic Aneurysm, intact or ruptured
• Repair by catheter based stent or by open surgery during monitoring
• Patent rectum
• Absence of rectal bleeding

Exclusion Criteria:

• Lack of informed consent
• Rectal bleeding
• Obstructed rectum