Our study emphasizes the role of both, the visceral and vascular surgeon, as an interdisciplinary team for a successful early treatment of mesenteric ischemia collaborating in accordance with an established algorithm in the era of advanced imaging and interventional options.
Angio-CT scan has become far more sensitive and is the imaging modality of choice for AMI. Therefore, the European Society of Vascular Surgery (ESVS) recommends angio-CT as initial investigation as class I, evidence level B [5]. In addition to the detection of involved vessels or the type of occlusion (thromboembolism, atherosclerotic, or dissection) the angio-CT can also show typical sequela of prolonged intestinal ischemia like gut wall thickening, free fluid/air, intestinal pneumatosis, or gas in the portal vein system. However, it has been documented that in AOCMI (acute-on-chronic mesenteric ischemia) around one-third of patients do not show any signs of ischemia on the CT scan [8]. This is consistent with our results where 54.6% of the patients with a diagnosed acute mesenteric ischemia did neither show any specific signs like intestinal pneumatosis or gas in the portal vein system, nor non-specific findings like free gas or fluid in the abdominal cavity. In this acute scenario, initial laboratory testing was not supportive in our results with huge variation in white blood cell count and serum lactate levels on admission [9, 10].
Thus, our threshold for explorative laparotomy was low and only patients with a short onset of symptoms and without the abovementioned findings on CT scan were rendered to primary endovascular approach. Out of those, who revascularization was judged as not feasible or did not seem promising, two patients survived throughout the long-term follow up, one of them after emergency bowel resection. This experience underscores the importance of the explorative laparotomy as a diagnostic and life-saving tool in the scenario of clinical symptoms without specific ischemia-related signs in the imaging.
Abdominal exploration followed by vascular bypass has been the standard of care for AMI, but there is increasing use of endovascular treatment with and without exploratory laparotomy. The use of mechanical and aspiration embolectomy, sometimes in combination with thrombolytic therapy, is often successful in offering a treatment alternative to open surgical revascularization [11]. Compared to open surgery the endovascular approach may be preferred in elderly and fragile patients and is supported by the current guidelines of the ESVS [5, 12]. Measurable advantages have been reported by Arthurs et al. showing reduced in-hospital mortality of 36% versus 50% in the surgically revascularized group with AMI. However, the majority of the patients were treated with an endovascular approach (n = 56) and only 10 patients received an open bypass surgery [13]. In a retrospective cohort with patients after endovascular intervention, Hsu et al. demonstrated that short time-to-reperfusion was significant in predicting survival for patients who underwent additional exploratory laparotomy. They concluded emergent endovascular treatment before laparotomy might be associated with a better survival [14]. Direct endovascular revascularization during laparotomy can be feasible but needs well-equipped imaging modalities and is so far not well established [15]. These results emphasize that a successful short-term treatment might be mainly a question of timing and that despite an endovascular approach, laparotomy remains a necessary life-saving treatment.
Due to the hospital-specific availability of the approach, a short time-to-reperfusion might be achieved by open revascularization, especially if the target vessel cannot be localized on imaging and signs for AMI are missing. In these cases, an explorative laparotomy is unavoidable. Zettervall et al. found in a large cohort with over 14.000 patients that despite the significant growth of endovascular interventions, the frequency of embolectomy for AMI remained unchanged and the rate of open surgery for chronic and acute mesenteric ischemia remained stable over 12 years. Meanwhile, annual population-based mortality for AMI decreased after both techniques [16]. Even at centers of excellence in endovascular treatment, 88% of patients between 1999 and 2010 underwent open revascularization, without dramatic changes in open treatment over time [6].
In the open approach, the visceral surgeon can assess accurately the intestinal viability, the extent of resection if needed, probable degree of intestinal recovery, and the need for a second look operation. In patients treated initially with an endovascular approach, this crucial part of treatment is lost or at least postponed. Additionally, if the bowel ischemia has already progressed to a certain degree, purely endovascular treatment might be unsuccessful. Frequently, bowel viability after reperfusion cannot be determined with certainty at the time of initial exploration. The frequency of bowel resection is higher during second-look surgery (53%) compared to the initial exploration (31%) which underlines the importance of a two-staged open approach [17].
Another important consideration supporting the open revascularization might be the potentially longer durability and patency compared to endovascular stenting. Though difficult to prove, as there is only limited data available, few sources documented a rate of re-stenosis in the first two years after stenting in chronic ischemia of 28–55% compared to publications on open bypass surgery with re-stenosis rate of 0–25% [3, 18–20]. As shown in one of our patients after endovascular treatment, repetitive interventions were necessary to keep the stent patent, which finally led to open revascularization. However, the individual decision in this emergency case may not be representative to draw a general conclusion for standard treatment, neither interventional nor surgical.
Considering the technical aspects, the iliac-mesenteric bypass via an anterior transabdominal approach is the easiest way to re-establish mesenteric perfusion in an emergency setting if thrombembolectomy is not indicated or feasible. Some authors advocate the so-called “French bypass” where the bypass passes the left renal pedicle [21]. The advantage of this approach has been described to avoid bypass kinking and providing enough length to adapt to movements of the SMA. The proximal anastomosis is retrograde on the left side of the infrarenal aorta. The course of the bypass runs first in the back and top of the retro-renal dissection plane, then loops behind and over the left renal pedicle, and finally turns downward and forward to the SMA. In our opinion, it is sufficient to use the ligament of Treitz as a pivot to avoid kinking of the bypass and create the "lazy C shape" bypass course (Fig. 1).
We use this technique routinely, which requires less retroperitoneal dissection.