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Dr Frank Veith (Riverdale, NY). Did you look at any of your excised specimens to see if there were microemboli, atheroemboli, in the colonic vessels? We agree with you that it is good to save hypogastrics, but together with Dr Mehta, we have collected more than 200 patients with unilateral hypogastric occlusion and more than 60 with bilateral hypogastric occlusion, and we have had no incidence of severe colonic ischemia. The patients who have had the colonic ischemia have all been without hypogastric occlusion, and they have all had the microemboli, so we think that is more important than just saving the hypogastric.

Dr Becquemin. Thank you, Dr Veith, for your comment. I am well aware of your paper on the topic and we also looked at the mechanisms of colonic ischemia. Unfortunately, this series is retrospective, and we have not specifically looked at microembolism in the excised specimens. However, 13 patients in the series had multiple microemboli in the legs, pelvis, and probably in the colon as well. We then agree that it is a very important issue.

Concerning the blockage of hypogastric artery, our figures are different, but contrary to your own study, our series included both open repair and EVAR, elective and rupture cases, and we concluded that it is better to save at least one hypogastric artery.

Dr Peter Gloviczki (Rochester, Minn). I enjoyed the presentation very much and thank you for calling attention to this very important complication. My question is, what do you use for intraoperative assessment of the colon in this type of patient and whether we should use it routinely or only selectively in patients with ruptured aneurysm? And my second question is, what should we do to decrease this complication? Should all patients with ruptured aneurysm undergo, within 24 hours, a sigmoidoscopy? I mean, the incidence that you show is very high, over 10%, so the yield may be quite high. So how do you assess the circulation postoperatively and what do you recommend to decrease this problem?

Dr Becquemin. During open repair, we routinely assess the colon with a Doppler probe following the repair of the aneurysm to decide whether the IMA should be reattached or left alone. Regarding rupture, it was our policy to use colonoscopy liberally, if not routinely. Unfortunately, once the colon is necrotic or severely ischemic, it is very rare to be able to save it with a delayed revascularization of the IMA or internal iliac artery. Again, as far as colon circulation is concerned, we inspect the back bleeding from the IMA, the gross aspect of the colon following restoration of flow, and the flow in the colon and ileal arteries with a Doppler probe.

Dr Roy Greenberg (Cleveland, Ohio). I have three questions for you. The first relates is whether prior colon surgery was included as one of the variables you assessed in your multivariable analysis, or were there not enough patients to really assess that?

The second question goes back to Dr Veith’s question, which is, were you able to categorize the etiology of the ischemia in any of these patients? For example, the patient you showed in your example probably had low flow as opposed to an embolic problem, given the proximity of the ischemia to the colonic anastomosis. If one were to hypothesize that hypogastric flow is important for colonic ischemia, the etiology would likely be flow/perfusion in nature rather than embolic, unless the management of such aneurysms requires undo manipulation.

My last is whether you looked at whether the left or right hypogastrics were involved in ischemia? Were they all the left side that was embolized or was it a mixture?

Dr Becquemin. Unfortunately, we had not prior colon surgery in the database, so we could not assess this item in the multivariate analysis. In the group of patients who had colonic ischemia, we found that three of them have a previous abdominal surgery.

The second question?

Dr Greenberg. Did you actually categorize patients with colonic ischemia where you had a specimen into low flow versus embolic?

Dr Becquemin. No, it was not done, and we think it was a very difficult question to answer since colon ischemia is probably multifactorial in origin. Your final question concerned the left side of the internal iliac occlusion. We did not specifically look at the side and I have not the answer to provide you with.

Dr Robert W. Hobson, II (Newark, NJ). I would like to return to the question regarding intraoperative testing. We also use the Doppler ultrasound methodology. Do you ever measure inferior mesenteric back pressure? And if you use Doppler or IMA back pressure measurements, are there characteristics of the Doppler method or pressure levels at which you would recommend reimplantation of the IMA?

Dr Becquemin. We have not measured the pressure. But we looked at the flow coming from the inferior mesenteric artery whether it was strong or weak or absent, and whatever the decision to reimplant or not the IMA, to assess the flow with a Doppler probe. We do not have levels to recommend except that in the absence of flow, every attempt must be made to restore the IMA. It is, however, difficult on this retrospective study to draw firm conclusions. We found no difference whether the inferior mesenteric artery was reattached or not. But since we have reimplanted the inferior mesenteric artery when the backflow was small and the flow weak, we have saved some colons.

Dr Alan B. Lumsden (Houston, Tex). One of the things we are unanimous, in addition to being surgeons, is that there are certain patients which are easy to predict, the patient who has got a patent IMA, who has got a celiac and an SMA stenosis is a setup for getting ischemia. Were there any direct anatomical risk factors that you could identify in these patients? A patent IMA, for example, would be an easy one which we exclude. Just the presence of a patent inferior mesenteric artery with an endograft would be a patient who we would consider more at risk and would need closer observation, for example.

Dr Becquemin. I agree that a fully patent IMA with stenotic celiac and superior mesenteric artery is at an increased risk of colon ischemia with EVAR. Unfortunately, it may be difficult to assess the IMA’s patency on CT scan alone. Sometimes, you think that it is patent because the trunk of the inferior mesenteric artery is visible on the CT scan. However, the ostium itself may be occluded. A preoperative angiogram may be useful but it is not in our routine practice.