A hybrid repair of a superior mesenteric artery pseudoaneurysm using open mesenteric bypass and endovascular exclusion

Abstract

Superior mesenteric artery (SMA) aneurysms and pseudoaneurysms are uncommonly encountered in vascular surgery practice, but they typically require repair. Historically, they have been repaired with open aneurysmorrhaphy, bypass and exclusion, or simple ligation. More recently, endovascular repair with coil embolization and stent graft exclusion have been advocated. We present a repair of an SMA pseudoaneurysm via a hybrid approach with common hepatic artery to SMA bypass, exclusion of the pseudoaneurysm with ligation of the SMA proximal to the bypass, plug occlusion of the proximal SMA, and coil embolization of the pseudoaneurysm.

Superior mesenteric artery (SMA) aneurysms and pseudoaneurysms are rare entities being encountered more frequently secondary to increased utilization of abdominal imaging (1, 2). When SMA aneurysms and pseudoaneurysms are discovered, most surgeons elect to repair them because of the 35% mortality rate associated with rupture, acute thrombosis, or embolization to the small bowel (3). Traditionally, repair has consisted of open SMA bypass with exclusion of the aneurysm or aneurysmorrhaphy. There have been multiple recent reports of endovascular repair either by stent graft exclusion or coil embolization of the aneurysm. We report a case of a 4.5-cm mid-SMA pseudoaneurysm repaired by a hybrid technique with open bypass and endovascular exclusion.

CASE DESCRIPTION

In 2008, a 76-year-old woman presented to an outside hospital with ischemic colitis. At that time, she underwent a total abdominal colectomy with end ileostomy followed by a complicated SMA stenting procedure. The patient had a long segment chronic dissection of the SMA that was treated with three 6 × 20 mm balloon expandable stents from the ostium of the SMA to mid-SMA. This procedure was complicated by the most proximal stent being misdeployed, with half of the stent residing outside the SMA in the aorta. Ultimately, this stent was snared and removed via an open femoral cutdown.

The patient subsequently came under our care for right lower extremity tissue loss in December 2011. An angiogram was performed that incidentally demonstrated a large mesenteric aneurysm. Computed tomography (CT) angiogram delineated the anatomy most clearly (Figure 1). An abdominal aortogram showed the large aneurysm involving the origin of the SMA and the stents (Figure 2).

Figure 1.

Preoperative CT angiogram demonstrating a 4.5-cm superior mesenteric artery pseudoaneurysm (arrow).

Figure 2.

Abdominal aortogram demonstrating a very large aneurysm involving the origin of the superior mesenteric artery (SMA) and the SMA stents (arrow). The SMA can be seen filling distal to the aneurysm.

The patient was then sent to the operating room for a hybrid open/endovascular repair of this pseudoaneurysm. We performed a common hepatic artery (CHA) to mid-SMA bypass with reversed greater saphenous vein. The SMA distal to the aneurysm, but proximal to the bypass anastomosis, was ligated to occlude the outflow of the pseudoaneurysm. The proximal SMA stent was cannulated from a femoral approach using a renal double-curve guiding catheter, and using the telescope technique, we advanced the guide catheter over a glide catheter and Bentson wire (Olympus America, Center Valley, PA) into the aneurysm. We then deployed an 8-mm Amplatzer plug (St. Jude Medical, St. Paul, MN) within the proximal stent after withdrawing the guide sheath into the aorta. This effectively occluded the inflow into the pseudoaneurysm. The exposed pseudoaneurysm was accessed from the abdomen with a 5 French sheath and the pseudoaneurysm was evacuated. Several intravascular coils were deployed into the pseudoaneurysm sac through the 5 French sheath (Boston Scientific, Marlborough, MA). The sheath was removed and the access site oversewn with 5-0 Prolene (Ethicon US, Somerville, NJ). The completion angiogram showed exclusion of the pseudoaneurysm sac with excellent filling of the distal SMA via the CHA-to-SMA bypass (Figure 3).

Figure 3.

Intraoperative completion sagittal angiogram demonstrating the proximal superior mesenteric artery (SMA) stent occluded by an Amplatzer plug (thin white arrow), the stent within the SMA as it exits the pseudoaneurysm (thick black arrow), the clip occluding SMA outflow (thin black arrow), and coils within the pseudoaneurysm sac.

The patient recovered uneventfully and was discharged home on postoperative day 7. CT angiogram was performed prior to discharge and confirmed exclusion of the pseudoaneurysm with sac shrinkage and patency of the CHA-to-SMA bypass (Figure 4). At 3-month follow-up, the patient continued to be asymptomatic. She died at another facility 4 months after the procedure due to line sepsis.

Figure 4.

Postoperative CT angiogram demonstrating the excluded superior mesenteric artery pseudoaneurysm without flow (arrow).

DISCUSSION

SMA pseudoaneurysms and aneurysms are rarely encountered but can potentially lead to significant morbidity and mortality (4). Historically, SMA aneurysms resulted from infections. However, more recently, atherosclerosis and collagen vascular disease have been reported as more common etiologies. Additionally, SMA pseudoaneurysms can occur from arterial dissection, pancreatitis, trauma, and iatrogenic sources (3).

Typically, SMA aneurysms affect the proximal 5 cm of the SMA. Approximately 90% of patients are symptomatic with abdominal pain or nausea and vomiting. They may also present with gastrointestinal hemorrhage. Half of patients will have a pulsatile mass or bruit (5).

SMA aneurysms and pseudoaneurysms have usually been repaired with aneurysmorrhaphy, exclusion, and bypass or, in some cases, ligation. The perioperative mortality ranges from 1.3% to 5%, with morbidity rates close to 10% (6, 7). Excellent long-term results have been achieved, with surgical repair providing good survival rates and protection from late aneurysm-related adverse events (6, 7). More recently, endovascular means to treat these aneurysms have been employed, with case reports and case series detailing both endovascular stent graft exclusion and coil embolization (3, 7). The ability to use endovascular techniques is limited by challenging target vessel access, arterial tortuosity, and the necessity to preserve side branches at or near the repair site; therefore, only a few totally endovascular repairs have been reported (7). Long-term follow-up in the endovascularly treated patients is not available, and the durability of these repairs is not firmly established.

Our patient's SMA pseudoaneurysm likely arose from previous manipulation with balloon-expandable stents within a chronic dissection. A totally endovascular repair was considered but abandoned due to the angulation constraints of the proximal inflow of the pseudoaneurysm and the outflow vessel. It did not appear that the anatomy of the SMA would accommodate a covered stent graft without causing significant kinking of the stent graft (Figure 2). A totally open operative repair of the SMA pseudoaneurysm was considered. However, because of the close proximity of the SMA pseudoaneurysm to the aorta, proximal control would have been obtained on the supraceliac aorta before opening the aneurysm, and an aorto-mesenteric bypass would have been necessary. Therefore, we chose a hybrid approach for this particular anatomy. The inflow to the pseudoaneurysm was excluded by an endovascular plug, avoiding the morbidity associated with supraceliac aortic cross-clamping. The SMA was ligated and revascularized distally with an extra-anatomic bypass. Coils were placed directly into the sac to ensure sac thrombosis.

Complications of endovascular therapy can lead to challenging anatomic situations. Pure endovascular or surgical rescue will often suffice. At times, a combination of these modalities is the best approach, as exemplified by this case. Utilizing both endovascular and open techniques can minimize the complexity and morbidity of the open procedure while maintaining the durability of the pseudoaneurysm repair.