Superior mesenteric artery transposition for acute mesenteric ischemia

Abstract

Superior mesenteric artery (SMA) transposition is a surgical technique previously described in the literature for the management of Nutcracker syndrome, SMA syndrome, and rarely their combination. However, its role in the successful treatment of acute mesenteric ischemia (AMI) remains unclear. A 55-year-old female patient presented to the emergency room of our institution with AMI and the computed tomography angiography findings of proximal SMA occlusion and bowel ischemia. After a failed attempt at retrograde open mesenteric stent procedure and ineligibility to undergo conventional surgical options for AMI, SMA transposition was performed with an end-to-side anastomosis of the SMA onto a healthy infrarenal aorta. Complete resolution of the symptoms was achieved in this case, and follow-up imaging at 6 weeks and 10 months showed a patent transposed SMA. This article describes the surgical technique for SMA transposition and highlights the novel application of this approach for AMI.

Acute mesenteric ischemia (AMI) is a group of pathological conditions caused by the abrupt interruption of the mesenteric blood flow resulting in bowel ischemia. Acute embolism is considered the most common cause of AMI; however, studies suggest a larger number of cases occurring due to in-situ thrombosis than previously reported.¹ Although AMI is rare with an incidence rate of 0.038%-0.050%,² clinical presentation in early stages can be nonspecific, making it challenging to diagnose. AMI is a surgical emergency, and a delay in diagnosis can lead to life-threatening complications. Mortality rates up to 50% have been reported in the literature.^2,3 For embolic or thrombotic AMI, the mainstay of therapy is rapid revascularization for restoring intestinal blood supply, and bowel assessment. Although numerous surgical procedures have been described for superior mesenteric artery (SMA) revascularization, in a rare circumstance when none of the established treatment methods for AMI could be utilized, we employed an innovative SMA transposition technique for rapid revascularization.

Case report

A 55-year-old female patient who is an active smoker presented to the emergency room in acute distress with 3 weeks of abdominal pain that acutely worsened in the past 2 days. On examination, she was found to have peritonitis. After the initiation of appropriate resuscitation and antibiotics, computed tomography angiography (CTA) was conducted, which showed evidence of proximal occlusion of the SMA and bowel ischemia (Fig 1). The vascular surgery team was consulted for the further management of AMI. Intravenous heparin infusion was initiated, and the decision was made to proceed for a surgical intervention in conjunction with general surgery.

Fig 1.

Sagittal (A) and axial (B) views of the preoperative computed tomography angiography showing occluded proximal superior mesenteric artery.

As there was a high suspicion of bowel ischemia in this patient, both teams agreed that exploratory laparotomy would be required. The SMA lesion on CTA imaging did not appear amenable to endovascular treatment due to the proximal occluded segment with bulky calcification. A hybrid operating room was not available at the time of the operation; therefore, a fluoroscopy compatible table and C-arm was utilized. Upon entry into the abdomen, the distal one-third of the ileum was clearly necrotic. This was resected by the general surgeon and left in discontinuity. A mesenteric angiogram revealed the occlusion of the origin of the SMA, which could not be crossed with a wire despite multiple attempts. Therefore, the retrograde open mesenteric stenting (ROMS) procedure was aborted (Fig 2). Due to the contaminated field, bypass with prosthetic material was also eliminated as an option.

Fig 2.

Angiographic images showing the occluded superior mesenteric artery (SMA) proximally (A) and patent distal SMA (B).

We elected to utilize the SMA transposition technique for revascularization in this case, as conventional options were lacking and the infrarenal aorta was noted to be disease-free on preoperative CTA. An end-to-side SMA to aortic transposition was performed without any complication (Fig 3). A strong pulse was palpable in the SMA, and the small bowel was pink after revascularization. The general surgeon performed temporary abdominal closure. Postoperatively, the patient was brought to the surgical intensive care unit with an open abdomen. She returned to the operating room the next day for bowel anastomosis and the closure of her abdomen. The patient had an unremarkable recovery and was discharged home on postoperative day 6 from her initial operation on aspirin 81 mg daily and apixaban 5 mg twice daily. At the postoperative visit at 2 weeks, her pain was resolved; she was able to tolerate a regular diet, and her surgical incision was well-healed. Subsequent CTA imaging at 6 weeks and a duplex ultrasound scan at 10 months postoperatively showed a patent SMA reconstruction with no areas of stenosis (Fig 4).

Fig 3.

Intraoperative image of superior mesenteric artery (SMA) transposition with end-to-side anastomosis on the infrarenal aorta.

Fig 4.

Postoperative computed tomography angiography showing the patent transposed superior mesenteric artery.

Surgical technique

The procedure for SMA transposition entails division of the proximal SMA and its re-implantation onto a segment of the infrarenal aorta that is devoid of calcification or atherosclerotic disease. Although technically feasible to perform via a retroperitoneal incision, we prefer the midline transperitoneal approach. It is critical to thoroughly review the preoperative CTA to evaluate the infrarenal aorta for identifying a likely site for anastomosis. The key steps of the surgery are described here.

Patient positioning

For the midline transabdominal approach, the patient is positioned supine on the operating room table, with arms abducted to 90°. A wide sterile preparation is employed from the nipples to the mid thighs.

Incision and abdominal exploration:

A midline incision is made starting at the level of the xiphoid extending down to the umbilicus. The incision can be extended inferiorly, if needed, for adequate exposure. Upon entry into the peritoneal cavity, the bowel is thoroughly examined, and any nonviable bowel, if present, is resected. Thereafter, revascularization ensues.

SMA exposure and mobilization:

The transverse colon is retracted superiorly, and the small bowel is retracted to the right side of the abdomen and covered with a moist towel. A mechanical retraction system is used for exposure. The ligament of Treitz is divided, and the duodenum is reflected to the right. The retroperitoneum is incised, and the infrarenal aorta is exposed. The SMA is generally nonpulsatile in AMI cases and is thus identified along the inferior margin of the pancreas by palpating for a firm tubular structure at the root of the mesentery. The SMA is dissected free circumferentially and encircled with a vessel loop; the dissection is extended proximally for 5-6 cm, nearly up to the origin of the SMA. In some cases, one to two proximal branches may require ligation.

Exposure of infrarenal aorta

Upon entry into the retroperitoneum, the infrarenal aorta is dissected free of the surrounding tissue. The anterior aortic wall is palpated to identify a soft, disease-free site for the anastomosis. The left renal vein is also mobilized and encircled with a vessel loop. Suitable aortic clamp sites are prepared with further dissection.

Division of proximal SMA

After preparation of the SMA and the aorta, a weight-based dose of intravenous heparin is administered for a goal activated clotting time of >250. The SMA is then clamped close to the origin and divided. The proximal end of the SMA is oversewn with two layers of a 4-0 prolene suture. The distal end is either spatulated or marked with sutures for orientation (Fig 5, A). The dissected length of the SMA is then brought over to the area identified for anastomosis over the infrarenal aorta, and with the retractors relaxed, the mobilized SMA is assessed for appropriate length and angulation for transposition.

Fig 5.

Diagrammatic representation of the key steps of the surgical technique for superior mesenteric artery (SMA) transposition. (A) Division and preparation of the proximal SMA for re-implantation. The SMA is marked with sutures for orientation. (B) End-to-side anastomosis in a running manner. (C) SMA anastomosed to the infrarenal aorta.

Aorto-SMA anastomosis and closure

After the SMA preparation, the aorta is clamped using either a side-biting clamp or an aortic cross-clamp. An arteriotomy is made over the anterior surface of the infrarenal aorta and fashioned to nearly the size of the SMA orifice to be transposed; alternatively, an aortic punch can be used to create an arteriotomy. An end-to-side anastomosis of the SMA onto the infrarenal aorta is performed with a running 5-0 prolene suture (Fig 5, B and C). Before the completion of the anastomosis, the SMA and aorta are flushed. The clamps are removed, and the anastomosis is inspected for hemostasis. Additionally, the retractors are briefly released to ensure that the anastomosis is devoid of undue tension or kinks. A pulse is palpable in the SMA at this point; a doppler probe can also be used to detect a multiphasic signal through the length of the SMA. After hemostasis is confirmed, the retroperitoneum is closed over the SMA and the aorta with 2-0 Vicryl sutures. The bowel is inspected again, and depending on the state of the bowel, either the abdominal cavity is closed in a multilayer manner, or temporary abdominal closure is performed.

Discussion

The conventional revascularization options for AMI include open surgical treatment, endovascular interventions, and hybrid interventions. Among the open options, surgical embolectomy is the ideal procedure for AMI with an embolic etiology, and an antegrade (aorto-mesenteric) or retrograde (ilio-mesenteric) bypass is more appropriate for in-situ thrombosis. Both prosthetic conduits and vein grafts can be used for mesenteric bypass, but if concerns exist for a contaminated field due to the necrotic bowel, prosthetic bypass is avoided. In such circumstances, even though a vein graft is a viable option, it can prolong the operative time, which is not feasible if the patient is critically ill, and a rapid surgical intervention is necessitated. In contrast, endovascular interventions offer the swiftness that is intended for the rapid restoration of blood flow in AMI while also being minimally invasive. These characteristics make endovascular techniques advantageous in carefully selected patients. Several options such as angioplasty, stenting, percutaneous embolectomy, pharmaco-mechanical thrombectomy, and thrombolysis are available and can be used in conjunction with one another. Evidence in the literature supports improved outcomes with the use of endovascular interventions as a primary modality for AMI, especially in thrombotic disease.^4,5 Nonetheless, endovascular procedures are not devoid of complications, for example, distal embolism and access-related complications, or limitations such as a contraindication to thrombolytic agents in patients with bleeding risk. Frequently, a laparotomy for bowel assessment is indispensable in patients with AMI, thus obviating the use of this option.⁶ ROMS is a hybrid procedure that offers the two-fold benefits of rapid revascularization through the endovascular technique and bowel assessment with laparotomy. Improved mortality outcomes and a technical success rate of up to 95% have been reported in the literature for ROMS in the management of AMI.⁷

The clinical case of AMI presented here had a unique scenario where the traditional revascularization options were not ideal and ROMS was aborted due to technical unfeasibility. Thus, an inventive approach with the re-implantation of the patent distal SMA onto the infrarenal aorta was instituted, with excellent outcome. This technique has several advantages in comparison with conventional revascularization procedures. The transposition procedure facilitates bowel evaluation and is a rapid approach for restoring mesenteric blood flow, as only one anastomosis is performed. As no prosthetic implants are involved, this technique is safe to perform in the presence of a contaminated field while also being considerably more expeditious compared with a mesenteric bypass. It is critical to understand that the success of this procedure is contingent on the availability of a disease-free site in the infrarenal aorta, along with the extent of SMA disease being limited to the proximal arterial segment and an adequate SMA length being available for reimplantation.

The relevance of this surgical procedure is not limited to its application in the treatment of AMI; rather, several studies have ascertained a role of this technique in the management of chronic vascular pathologies, such as SMA syndrome (SMAS) and Nutcracker syndrome (NCS), and rarely in the management of a clinical presentation with coexisting SMAS and NCS.8, 9, 10 In our practice, we have also successfully used SMA transposition to treat a patient presenting with concomitant SMAS and NCS. By re-implanting the SMA onto the disease-free infrarenal aorta, the compression on both the duodenum and left renal vein is released, thus addressing both conditions. Furthermore, successful revascularization in AMI with this technique indicates a potential role of this surgical procedure in the treatment of chronic mesenteric ischemia in a select group of patients, including septic cases, heavily calcified cases, and diseased proximal SMA cases.¹¹

Conclusions

SMA transposition is a surgical technique with excellent versatility. It can be used not only for chronic vascular conditions such as NCS and SMAS but also for acute clinical presentations such as AMI. In cases where endovascular treatment is not feasible, or a contraindication to the use of a prosthetic graft arises due to contaminated fields, SMA transposition offers a rapid and efficient approach for revascularization.

Patient consent

The patient included in this manuscript has consented to the publication.

Author Contributions

Conception and design: OS, PB, AL, KV, DK, BT, DS

Analysis and interpretation: OS, KV, DS

Data collection: OS, AL, DS

Writing the article: OS, AL

Critical revision of the article: OS, PB, AL, KV, DK, BT, DS

Final approval of the article: OS, PB, AL, KV, DK, BT, DS

Statistical analysis: Not applicable

Obtained funding: Not applicable

Overall responsibility: OS, PB, AL, KV, DK, BT, DS

Funding

None.

Disclosures

None.

From the New England Society for Vascular Surgery