Hybrid surgery for imminent rupture of superior mesenteric artery aneurysms

Abstract

A case of a superior mesenteric artery aneurysm presented with an impending rupture. The aneurysm was located in the right side branch of the superior mesenteric artery. The patient underwent an emergency hybrid procedure, which included aneurysm embolization and exclusion of the aneurysm with an endoluminal stent graft. The blood supply to the right side branch was restored by bypass grafting with an autologous vein graft. The postoperative course was uneventful with no evidence of mesenteric ischemia. Postoperative computed tomography angiography confirmed complete aneurysm exclusion and sac size reduction, as well as patency of the stent graft and bypass.

Superior mesenteric artery aneurysm (SMAA) is rare entity with a prevalence of 0.1 to 0.2 %, accounting for 3.5% to 8.0% of all visceral arterial aneurysms.^1,2 SMAA presents a potentially life-threatening situation owing to the risk of fatal rupture, embolism, and infection through erosion of adjacent visceral organs.³ Although treatment should be individualized on the basis of anatomy and characteristics, an endovascular-first approach, if feasible, has been recommended strongly.^2,4 However, a challenge of the endovascular treatment lies in achieving the successful aneurysmal exclusion while maintaining sufficient blood flow in major tributaries.^5,6 Here, we present a case of demonstrating the successful management of the impending rupture of SMAA. Stent grafting avoided injuries to adjacent organs that could have been caused by the surgical exposure of the SMA orifice. The endo-sacrificed intestinal blood flow was restored through a bypass using an autologous saphenous vein graft. The patient provided written informed consent for the report of his case details and imaging studies.

Case report

A 64-year-old man with no significant medical history presented to the emergency department with a 3-day history of worsening upper abdominal pain. The pain started acutely and seemed very severe. He had a blood pressure of 94/58 mm Hg, a pulse of 68 beats per minute, and a body temperature of 36.7°C. Laboratory testing showed no indications of inflammatory or infectious diseases. A contrast-enhanced computed tomography (CECT) revealed the SMA aneurysm behind the pancreas and the CT value surrounding it was slightly elevated. The diameter of the aneurysm was 35 mm in width and 45 mm in length (Fig 1). The SMA trunk was branched immediately into two systems: the left side branch supplied the jejunal arteries, and the right side branch gave rise to the ileal, ileocecal and right and middle colic artery (MCA). The SMAA was located in the proximal portion of the right side branch and involved the origin of the MCA. No evidence of additional aneurysmal changes, dissections, or connective tissue disorders was identified in other part of his body.

Fig 1.

CECT scan shows the aneurysm in the SMA trunk. The red area indicates the extent of the aneurysm. CECT, contrast-enhanced computed tomography; SMA, superior mesenteric artery.

Judging from the symptoms and CT image, there was a high risk of rupture. Thus, immediate surgery was proposed. In an open approach, it was necessary to mobilize both the pancreas and the duodenum, a procedure known as Kocher's maneuver, to reach the proximal neck of the SMAA. An endovascular approach was considered because there was a 30-mm proximal sealing zone. However, the aneurysm was hanging just beneath the bifurcation point. Therefore, stent grafting required sacrificing a major branch of the SMA. Accordingly, we devised a hybrid therapy that involved the implantation of stent grafts from the SMA trunk to the left side branch, while the compromised blood flow in the right side branch was restored by bypass surgery.

Under general anesthesia, a 15-cm of midline incision was performed. The mesenteric membrane was briefly incised to expose the distal part of the aneurysm (Fig 2). The origins of right colic artery and ileocolic artery were identified. The jejunal artery originated from the left-side branch was identified and an 8F introducer sheath was inserted in a retrograde fashion. We chose two distinct sizes of peripheral stent grafts (VIABAHN, W. L. Gore & Associates, Flagstaff, AZ), which were 10 mm to 50 mm in proximal and 9 mm to 50 mm distal, to accommodate the change in thickness from 9 mm to 7 mm in diameter of the target vessels. Furthermore, the use of the balloon-expandable stent graft for indications beyond iliac artery stenosis is not covered currently in the national health insurance in this country. The MCA was not identified within the surgical field. Therefore, an 18-mm vascular plug (Amplatzer Vascular Plug II, Abbott Vascular, Santa Clara, CA) was placed within the aneurysm to facilitate thrombosis.⁷ The right side tributaries were dissected from the aneurysm, and its end was sewn closed. A saphenous vein graft was harvested, because the use of synthetic graft would result in an incongruous size mismatch with the SMA branches. Bypass was established with the proximal anastomosis situated on the left side branch and the distal anastomosis positioned on the right side tributaries (Fig 3). It was located within the mesenteric membrane. The pulsation of the marginal arteries was confirmed. Neither angiography or indocyanine green test detected mesenteric, intestinal, or colonic perfusion impairment. Although we sacrificed the origin of the MCA, no cyanotic coloration was observed throughout the colon. The operating time was 163 minutes, with the amount of blood loss being 210 mL.

Fig 2.

Vessels with blue ribbons are peripheral tributaries of the right side SMA branch including ICA and RCA. The distal part of the SMA aneurysm is encircled by a small red ribbon. The vessel marked with a large red ribbon is jejunoileal artery, originating from the left side SMA branch. ICA, ileocolic artery; RCA, right colic artery; SMA, superior mesenteric artery.

Fig 3.

Schematic presentation of the hybrid procedure. The mesenteric membrane was briefly incised along the dashed line. The incision was closed to locate the bypass graft inside the membrane. ICA, ileocolic artery; JIA, jejunoileal artery; RCA, right colic artery; SMAA, superior mesenteric artery aneurysm; SVG, saphenous vein graft.

Postoperatively, complete resolution of the symptoms was achieved. On postoperative day 1, the functionality of the stent graft and bypass graft was verified by CECT (Fig 4) before initiating oral intake. Dual antiplatelet therapy consisting of clopidogrel and aspirin was introduced. The patient recovered uneventfully and was discharged on postoperative day 10.

Fig 4.

Contrast-enhanced computed tomography (CECT) confirmed the complete exclusion of the aneurysm and the patency of the stent graft and bypass graft (blue).

Discussion

SMAAs are rare diseases, but they are identified more frequently detected owing to the advancements in diagnostic imaging technologies.¹ The silent aneurysms can be managed effectively by vigilant monitoring and timely intervention when deemed necessary.^3,7 However, symptomatic visceral artery aneurysms are crucial conditions that demand swift intervention, because their rupture is closely tied to a notable mortality risk. Open surgical procedures for SMAAs include aneurysm resection coupled with revascularization if required.⁶ The surgical exposure of the proximal portion of the SMA posed a challenge, carrying an elevated risk of intraoperative aneurysm rupture and potential injury to adjacent organs, including the pancreas, duodenum, and abdominal nerve plexus.⁸ Although a guideline recommends an endovascular-first approach, the straightforward implantation of stent grafts in this case would have resulted in unacceptable compromise to the right and ileocolic arterial blood flow.⁴ Our hybrid strategy was successful in excluding the aneurysm by endovascular procedures while preventing injuries to the adjacent organs and ensuring adequate perfusion through surgical revascularization. Furthermore, retrograde open insertion of the SMA stent grafting facilitated more precise device deployment than the transfemoral approach.⁹ The use of autologous vein grafts instead of prosthetic conduits might avoid the issues of bacterial infection and size mismatch.¹⁰ When determining the specifics of the bypass surgery, including anastomotic sites and the selection of a branch for arterial flow restoration, careful consideration tailored to the individual case is crucial.^11,12

Assessing mesenteric perfusion is crucial. There are limited intraoperative tools available for making decisions regarding intestinal viability. Colorectal surgeons rely on manual examination and visual observation to identify signs such as peristalsis and mesenteric pulsation. Pulse oximetry, visible light spectrophotometry, Doppler ultrasound examination, laser fluorescence angiography, and laser Doppler flowmetry represent the established methodologies for clinically assessing intestinal viability during surgery.¹³ CT angiography is required to assess postoperative intestinal perfusion. When considering a second-look surgical procedure, a laparoscopic approach may be useful.¹⁴ Further investigation is needed to investigate the potential benefits of combining different modalities for intraoperative and postoperative evaluation of intestinal viability.

Conclusions

We have reported successful treatment of symptomatic SMAAs with a hybrid therapy comprising endovascular stent grafting and bypass grafting. As previously documented in the literature, this is the first report of its kind. While treatment decisions should be based on individual and case-specific considerations, this combination appears promising for mitigating the surgical invasiveness and associated morbidities observed in patients with symptomatic SMAAs.

Disclosures

None.