Embolization of the internal iliac artery: still more to learn.

ONE thing that makes interventional radiology such a stimulating career is the constant evolution of our techniques for new clinical applications. Consider the lowly hypogastric artery: so essential to fundamental organs of elimination and reproduction, yet we embolize it with impunity in cases of pelvic trauma or obstetric hemorrhage, and stent over it to treat iliac occlusive disease with hardly a second thought. Catheters practically fall into it. Not a subject for deep intellectual discourse during morning rounds—until now. Two new procedures have fascinated the interventional radiology community and caused us to consider internal iliac artery embolization in far more detail than in the past. For uterine fibroid embolization, we plumb the depths of the anterior division. Hours of scientific and teaching conferences are spent debating which catheters to use, where to embolize, which collaterals matter, what size particles to use, endpoints for embolization, and what drugs to administer intraarterially, intravenously, orally, and rectally. After 30 years of embolizing hypogastric arteries, how could we know so little? We have to learn (or re-learn) the arterial anatomy of the ovary, the hormonal pathways of the menstrual cycle, and the control of pelvic pain. We have forged relationships with a new group of patients and referring physicians. Stent-graft repair of abdominal aortic aneurysms focuses our attention on the opposite end of the internal iliac artery. Patients in whom the stent-graft covers the origin of an internal iliac artery may be at risk for ischemic complications, or for a type II endoleak due to retrograde flow up the internal iliac. In this issue of JVIR, reports from Montifiore, Stanford, and Massachusetts General Hospitals (1–3) examine the management of the internal iliac artery under these circumstances. As with uterine fibroid embolization, more questions are raised than are conclusively answered. Indications for extension of a stent-graft limb into the external iliac artery include insufficient length of common iliac artery for distal attachment, aneurysm of the common iliac artery, or aneurysm of the internal iliac artery. At the University of Pennsylvania, as at Montifiore, all patients whose stentgrafts are designed to cover the internal iliac artery undergo embolization preoperatively. In contrast, only some patients undergo embolization at the Massachusetts General Hospital. No selection criteria are given in the Stanford report. Do all these patients need to undergo embolization? The Massachusetts General Hospital experience would suggest not because 18 of 31 internal iliacs (58%) that were covered by a stent-graft did not receive preoperative coil embolization, yet they report no endoleaks. This suggests that hypogastric embolization may not be necessary if a stent-supported graft limb is used with a sufficiently oversized diameter to make a tight seal somewhere along the course of the common iliac artery. If the common iliac artery is aneurysmal to within 1.5 cm of its bifurcation, then the internal iliac artery should be embolized preoperatively to prevent an endoleak. Any unsupported graft, such as the Ancure or Montifiore graft, will not form a seal except at their distal touchdown sites, and so hypogastric embolization is required when these grafts are extended into the external iliac artery. Occlusion of the internal iliac artery cannot be performed with impunity in these patients. Unlike the trauma and obstetric populations, who rarely develop ischemic complications after ligation or embolization of the internal iliac artery, patients with advanced aneurysmal atherosclerotic disease may lack the normally rich collateral network in the pelvis. All three series report a substantial complication rate of 26%–41%. The most common complication, seen in approximately 20%–40% of patients, was buttock claudication, which could be disabling. Claudication improved over time in most patients but some remained disabled until death. A few patients developed new onset of sexual or bladder dysfunction, which emphasizes the importance of obtaining a sexual history in patients before and after stent-graft placement, and of discussing the risk of impotence in the consent process. One patient on prolonged bedrest developed a sacral decubitus ipsilateral to the embolized hypogastric artery. There were no instances of bowel ischemia, although this has been reported previously after aortic stent-graft re