Surgical and endovascular techniques for mesenteric revascularization

INTRODUCTION — Acute or chronic stenotic or occlusive lesions of the celiac, superior mesenteric, or inferior mesenteric arteries can lead to mesenteric ischemia due to inadequate intestinal perfusion. When presenting acutely, the etiology is usually due to embolism to superior mesenteric or celiac arteries, thrombosis of an existing atherosclerotic arterial stenosis, traumatic injury, or spontaneous mesenteric dissection. When presenting as a chronic issue, the etiology is usually due to stenosis at the origin(s) of the mesenteric arteries due to atherosclerosis [1]. The pattern of chronic disease is frequently multivessel in nature, and patients present either acutely with intestinal catastrophe (ie, acute-on-chronic ischemia) and necrosis or more insidiously with chronic symptoms of postprandial pain, food fear, and cachexia.

The surgical and endovascular techniques used to revascularize the mesenteric vessels are reviewed. The clinical features, diagnosis, and nonsurgical management strategies for managing acute or chronic ischemia due to arterial occlusion are reviewed elsewhere. (See "Acute mesenteric arterial occlusion" and "Chronic mesenteric ischemia".)

The management of other forms of acute mesenteric ischemia including mesenteric venous thrombosis and nonocclusive mesenteric ischemia, which are primarily managed medically with supportive care with or without anticoagulation, are reviewed separately. (See "Mesenteric venous thrombosis in adults" and "Nonocclusive mesenteric ischemia".)

MESENTERIC ANATOMY AND TARGETS FOR REVASCULARIZATION — Adequate knowledge of visceral vessel configuration, collateral circulation, and associated anatomy is critical to understanding the clinical evaluation and treatment of mesenteric ischemia. The mesenteric vessels include the celiac artery, superior mesenteric artery (SMA), and inferior mesenteric artery (IMA), which arise from the abdominal aorta (figure 1). Embolism as a cause of acute mesenteric ischemia preferentially occurs in the SMA (passing by the celiac artery) because of the gentler takeoff of the SMA from the aorta. The embolism typically lodges beyond the origin of the middle colic, thus sparing the proximal jejunum. Atherosclerotic lesions producing chronic mesenteric ischemia typically occur at the origin of the mesenteric vessels. There is rich collateralization (figure 2) between the mesenteric vessels, and classically, stenosis or occlusion of two of the mesenteric arteries is required to produce symptoms of chronic mesenteric ischemia.

●Celiac artery – The celiac artery arises at spinal level T12 and is the first branch of the aorta in the abdomen just beyond the crus of the diaphragm. The celiac artery supplies the foregut with blood supply via the common hepatic, splenic, and left gastric arteries [2]. The treatment of celiac artery alone in chronic mesenteric ischemia is associated with the highest rate of symptomatic recurrence [3], and typically, this vessel is only revascularized in combination with the SMA.

●Superior mesenteric artery – The SMA arises at spinal level L1 as the second named vessel in the abdomen. The SMA supplies the majority of the small intestines (figure 1) as well as portions of the ascending and transverse colons via the middle, right, and ileocolic arteries (figure 3) [4]. The proximal SMA may provide the inflow for a replaced hepatic artery (figure 4).

●Inferior mesenteric artery – The IMA arises at the level of L3 and supplies the transverse and descending colons. The marginal artery of Drummond and arc of Riolan collateralize the IMA with the SMA.

Targets for revascularization — The SMA is the primary target for revascularization. There is reasonable evidence that treatment of the SMA alone in patients with chronic mesenteric ischemia is adequate [5,6], although some authors suggest treatment of both the SMA and celiac artery, if possible [7,8]. Similar to the celiac artery, the IMA is a secondary, rather than primary target of mesenteric revascularization, although while mesenteric ischemia primarily affects the small bowel, there have been reports of chronic ischemic colitis arising from stenosis or occlusion of the IMA [9]. (See "Colonic ischemia", section on 'Chronic ischemic colitis'.)

INDICATIONS AND TECHNIQUE SELECTION — The primary indications and technique selection for mesenteric revascularization depend on the acuity of the presentation (acute, chronic), etiology of the disease (embolic, thrombotic), lesion characteristics, and patient factors.

Acute mesenteric ischemia — For patients with mesenteric ischemia due to mesenteric arterial occlusion, revascularization should occur urgently or as an emergency for patients who demonstrate evidence of bowel ischemia. This may include acute onset abdominal pain that is "out of proportion" to the physical examination in the setting of vascular imaging (usually computed tomographic angiography) consistent with mesenteric artery occlusion and laboratory studies suggesting metabolic acidosis with elevated lactic acid and leukocytosis. (See "Overview of intestinal ischemia in adults", section on 'Clinical features'.)

The operative and interventional techniques selected for acute mesenteric ischemia are procedures that can be performed expeditiously. The sooner blood flow is restored to the ischemic bowel, the better the outcome for the patient. In addition, the ability to assess the intestines for irreversible necrosis is crucial in determining the viability of the bowel and resecting any nonviable segments. As such, endovascular techniques are not commonly selected in the setting of acute mesenteric ischemia, with some exception.

●For patients with mesenteric embolism, open mesenteric artery embolectomy quickly restores blood flow. (See 'Superior mesenteric artery embolectomy' below.).

●For patients with thrombosis of existing atherosclerotic lesions, thrombectomy would not be successful in achieving long-term patency, and as such, techniques that correct the culprit lesion and inspect the intestines such as open mesenteric bypass or retrograde open mesenteric stenting can be used, depending upon patient and inflow vessel characteristics. (See 'Mesenteric artery bypass' below and 'Retrograde open mesenteric stenting' below.)

●For patients with spontaneous mesenteric artery dissection, bowel ischemia rarely develops, but if there is compromised flow, these patients can be treated using open or endovascular options. (See "Spontaneous mesenteric arterial dissection".)

●For patients with traumatic lesions, the approach will depend upon the extent of the injury and may be amenable to open or endovascular techniques. (See "Abdominal vascular injury", section on 'Mesenteric arteries'.)

Chronic mesenteric ischemia — Patients with symptomatic chronic mesenteric ischemia with vascular imaging suggesting multivessel mesenteric occlusive disease can proceed with revascularization on an elective basis once other potential causes of abdominal pain have been excluded with an appropriate clinical evaluation including esophagogastroduodenoscopy, colonoscopy, and abdominal imaging. The patient should also be optimized for the procedure from a medical standpoint. The symptoms of chronic mesenteric occlusion usually include the insidious onset of postprandial abdominal pain, food fear, and weight loss, or nonspecific symptoms such as nausea/vomiting, diarrhea, or constipation. (See "Chronic mesenteric ischemia", section on 'Clinical presentations'.)

Endovascular and open surgical options are available for revascularization of chronic mesenteric lesions, with the primary intent to restore flow to the superior mesenteric artery in most cases. Overall, given the lower rate of perioperative complication rates with similar short- and long-term mortality, endovascular revascularization is typically recommended if the culprit lesions are amenable to endovascular treatment. An open surgical technique is preferred for endovascular failures and for arterial lesions such as flush aortic occlusions or lesions that are severely calcified or long or tandem in nature. The selected approach depends on patient comorbidities, lesion characteristics accounting for the patient's life expectancy, and the durability of the revascularization.

There have been no prospective randomized trials comparing open with endovascular treatment, but most centers have shifted toward mesenteric stenting as the first-line treatment in chronic mesenteric ischemia. Endovascular treatment is associated with lower morbidity and a shorter hospital length of stay, with similar mortality and overall survival compared with mesenteric bypass [10,11]. Perioperative complications occur more frequently with open revascularization, but recurrence rates are higher for endovascular revascularization [12]. Open reconstruction is very durable, with lower rates of restenosis compared with mesenteric stenting (15 versus 37 percent), better primary patency rate (86 versus 51 percent), higher freedom from recurrent symptoms (13 versus 30 percent), and lower rates of reintervention (9 versus 20 percent) [13,14]. Primary patency of open bypass is 89 percent at five years with 93 percent freedom from reintervention, while covered stents have 92 percent primary patency at three years, reaching similar levels as open bypass [14,15]. (See 'Mesenteric artery bypass' below.)

PATIENT PREPARATION

Medical evaluation — The underlying reason for mesenteric revascularization guides the preoperative preparation. The acuity of the clinical presentation often dictates the available time for medical evaluation and optimization and urgency of revascularization.

●Acute mesenteric ischemia – Patients with acute mesenteric ischemia require aggressive fluid resuscitation, as they often present with abdominal sepsis. Given the broad range of differential diagnoses, there is often a delay, further increasing the importance of resuscitation and the need for emergency intervention. In addition, if there is any concern for bowel ischemia/necrosis, antibiotics should be initiated. Ideally, vasopressors should be avoided whenever possible, as use of these agents may exacerbate intestinal ischemia. If needed due to the patient's condition, the best choice is low- to mid-dose dopamine and epinephrine, taking care to avoid pure alpha-adrenergic agents. Systemic anticoagulation (eg, intravenous unfractionated heparin) should also be initiated as soon as the diagnosis has been made to limit clot propagation.

●Chronic mesenteric ischemia – Patients with chronic mesenteric ischemia have a high incidence of concomitant coronary artery disease and should undergo medical evaluation and cardiac clearance once other causes of abdominal pain have been ruled out. Pulmonary function should also be evaluated and optimized. (See "Evaluation of cardiac risk prior to noncardiac surgery" and "Evaluation of perioperative pulmonary risk".)

Noninvasive imaging of the carotid arteries and lower extremities should also be undertaken given the high incidence of arterial disease in other vascular beds. For patients in whom mesenteric bypass is selected, it is important to know the extent of aortoiliac disease, as this will influence the choice of inflow vessel. Computed tomographic angiography is also necessary to evaluate the ability to clamp the infrarenal and supraceliac aorta and the suitability of the iliac arteries to serve as inflow, if needed.

Patients with chronic mesenteric ischemia are often malnourished and require full evaluation of their nutritional status. Prolonged delays to intervention should be avoided. Those with mild symptoms should be counseled to avoid large meals, while those with severe malnutrition may need preoperative nutrition support. (See "Clinical assessment and monitoring of nutrition support in adult surgical patients" and "Overview of perioperative nutrition support", section on 'Preoperative nutrition support'.)

Antiplatelet therapy prior to mesenteric stenting — Patients in whom endovascular revascularization is planned (eg, chronic mesenteric ischemia) are often taking antiplatelet agents, and daily dosing should not be withheld. It is often difficult to know if mesenteric artery revascularization will be successful, so we do not routinely alter a prior regimen or provide any loading dose. If a decision is made intraoperatively to perform mesenteric stenting, a loading dose of clopidogrel can be provided in the recovery room. (See 'Postoperative course' below.)

No role for bowel preparation — Routine bowel preparation is not required and should be avoided in patients with severe abdominal symptoms or subacute ischemia. Bowel preparation delays time to revascularization and can exacerbate ischemia, potentially increasing the risk for intestinal necrosis.

ENDOVASCULAR TECHNIQUES

Principles of endovascular therapy — The majority of endovascular procedures for mesenteric ischemia are performed via a percutaneous approach, although hybrid open procedures have been described. (See 'Retrograde open mesenteric stenting' below.)

The choice of access vessel depends on the anatomy of the artery being treated. When percutaneous access is used at any site, real-time ultrasound guidance is recommended to directly image the needle entering the artery at an access point that is free of disease, away from large branching vessels, and in an area that can be easily compressed or treated with a closure device postprocedure. (See "Percutaneous arterial access techniques for diagnostic or interventional procedures".)

Common femoral artery and brachial artery access have been used to treat mesenteric arterial occlusions. Brachial artery access is appealing given the acute downward route of the superior mesenteric artery (SMA), which makes selection and crossing of lesions easier compared with a femoral approach; however, brachial artery sheath hematoma can lead to neuropathy [16]. For this reason, some practitioners prefer brachial artery cutdown for arm access given the larger sheath size for the stents that will be used, which eliminates this risk and allows direct repair of the access artery. If percutaneous access is used, ultrasound guidance is preferred regardless of the approach to allow direct visualization of the needle entering the artery in an access point that is free of disease, away from large branching vessels in an area that can be compressed easily postprocedure.

Appropriate sheath placement in the aorta provides support for wires and crossing catheters used to navigate stenoses. Positioning of the C-arm is crucial in achieving an adequate view of the pathology being treated. This usually requires a relatively steep oblique or lateral view given the anterior direction of the mesenteric vessels from the aorta but will depend on the patient's individual anatomy. Distal mesenteric vessels are best viewed from an anterior-posterior positioning of the C-arm.

Mesenteric vessels tend to spasm, so wire manipulation should be minimized. The use of embolic protection devices during intervention has been suggested, with 66 percent of filters retrieving debris in mesenteric revascularization cases in one study [17].

Mesenteric stenting — For patients with chronic mesenteric ischemia due to atherosclerosis, revascularization of the superior mesenteric artery is the main goal; stenting the celiac artery may be a secondary goal.

Mesenteric intervention has evolved from primary angioplasty to primary mesenteric stenting [16,18-21]. Balloon-expandable covered stents are frequently used, given their short lengths and superior radial force, as well as better patency compared with uncovered stents [22]. Freedom from restenosis with covered stents is higher compared with uncovered stents (92 versus 52 percent), as is freedom from symptom recurrence (92 versus 50 percent, respectively). Factors associated with lower success rates using an endovascular approach include flush aortic occlusions or lesions that are long or multisegmental in distribution. Patients with these anatomic features should be considered for open intervention.

Unlike chronic mesenteric ischemia, the use of mesenteric stenting in acute mesenteric ischemia has not been universally embraced, although it has been described and thought to be technically noninferior compared with open procedures, with significant selection bias [23-25]. Patients with acute mesenteric ischemia need rapid revascularization and don't have the luxury of time needed for many endovascular techniques. In addition, these patients need to have their bowels inspected for ischemic necrosis, which is not readily available using an endovascular approach. If endovascular revascularization is used for acute mesenteric ischemia, depending on the expediency of revascularization and the patient's clinical condition, the entire length may need to be evaluated, either with laparotomy or laparoscopy, to determine if there are any areas of frank necrosis requiring resection [26].

Mechanical thrombectomy and lysis — The use of a minimally invasive approach for acute mesenteric ischemia has been described, but given the prolonged treatment time for this therapy and the time-sensitive nature of the diagnosis, it is often not used as a solo technique [23,24]. One option is initial endovascular management with a mechanical thrombectomy device to allow intestinal reperfusion followed by placement of a lysis catheter to resolve residual thrombosis [27]. The success rate for revascularization using this technique was 87 percent among 70 patients with acute mesenteric ischemia (65 percent thrombotic, 35 percent embolic) [28]. Laparotomy was needed in 69 percent, and overall mortality was 36 percent. These numbers compare favorably with open procedures, suggesting this may be an option for patients who would not tolerate surgical intervention.

Retrograde open mesenteric stenting — For some patients with chronic mesenteric ischemia, conditions are present that prevent an endovascular technique from being technically achievable (eg, flush occlusion, long segment disease, excessive calcification, access vessel disease/occlusion). In these patients, a hybrid approach using retrograde open mesenteric stenting (ROMS) may be feasible, which limits the hemodynamic and physiologic insults that occur during open surgical revascularization but provides the means for an endovascular repair in those who otherwise cannot undergo a percutaneous endovascular repair.

For patients with acute thrombotic occlusion, ROMS allows inspection of the bowel while providing more rapid revascularization compared with mesenteric bypass. Unanticipated reinterventions and mortality are comparable with open surgical bypass, and it has been suggested that with the shorter operative time, ROMS should be considered a first-line option in this subset of patients [29].

To perform ROMS, the SMA is approached surgically as described (see 'Mesenteric artery bypass' below), but more distal SMA exposure is required to provide enough length of patent SMA in which to place the sheath. Once the SMA is exposed, the artery is then accessed with a sheath, and an arteriogram is performed. The lesion is then crossed in a retrograde fashion, and angioplasty and stenting are performed as previously described (see 'Mesenteric stenting' above). The artery can be closed primarily or patched, depending on the size of the sheath needed for stenting, and the access vessel may require patch closure to prevent future stenosis.

In a retrospective review of 34 patients who underwent ROMS at a single institution, primary patency at one and three years was 70 and 61 percent, respectively, with primary assisted and secondary patency rates of 87 and 97 percent, respectively, at three years [30]. The technical success rate was 91 percent, and 95 percent of patients were free of any symptom reoccurrence at three years.

OPEN TECHNIQUES

Principles of open surgical revascularization — Acute and chronic mesenteric ischemia are potentially life-threatening problems to the patient, and both frequently have a delay prior to diagnosis.

●The patient should be prepared from the nipples to the knees to allow for possible saphenous or femoral vein harvest.

●A nasogastric or orogastric tube should be placed to decompress the stomach and to aid in the identification of the esophagus.

●The bowel should be evaluated along its entire length, but ischemic bowel should not be resected prior to the mesenteric revascularization, unless it is frankly necrotic or perforated. After revascularization, the reperfused bowel is examined again for viability. Returning to the operating room for "second-look" operation is often required to assess any bowel with questionable viability. (See 'Adjunctive procedures' below.)

●Following open surgical revascularization, the retroperitoneal tissue over the aorta or iliac arteries, the ligament of Treitz, and peritoneum over the superior mesenteric artery (SMA) are reapproximated to provide a layer of tissue between the intestines and the grafts to avoid complications related to fistula formation. If the retroperitoneal tissue does not close easily, an omental flap can be used to cover the graft. (See "Aortoenteric fistula: Recognition and management".)

Superior mesenteric artery embolectomy — Exposure of the SMA for embolectomy is done through a midline laparotomy.

The transverse colon is elevated superiorly, and the small bowel is moved to the right side of the patient. The visceral peritoneum below the third portion of the duodenum is incised over the SMA to expose the vessel for thrombectomy. There is no need to mobilize the ligament of Treitz with this exposure. Any replaced or accessory hepatic arteries need to be identified and preserved. (See 'Mesenteric anatomy and targets for revascularization' above.)

While a Doppler signal can sometimes be heard in the vessel, care must be taken to avoid being misled by the water hammer pulse heard just proximal to the level of the occlusion.

The SMA is then opened either transversely or longitudinally. Thrombectomy is performed using Fogarty catheters, which are sized to the diameter of the vessel. These are passed both retrograde and antegrade until a clean pass without thrombus is made. Transverse arteriotomy can be closed primarily with interrupted sutures, while longitudinal arteriotomy requires patch closure to prevent narrowing of the artery. If necessary, a transverse arteriotomy can be extended longitudinally to perform a surgical bypass if thrombectomy attempts fail.

Mesenteric artery bypass

Selecting an approach — Mesenteric artery bypass can be accomplished using inflow from the supraceliac aorta (ie, antegrade approach) or using inflow from the distal aorta or iliac arteries (ie, retrograde approach). The long-term and major complication rates are similar for antegrade and retrograde mesenteric bypass [15]. Preoperative computed tomographic angiogram is necessary to evaluate the suitability of the aorta or iliac arteries for clamping and sewing the bypass. Selecting which approach to use is based on several factors.

●The advantage of antegrade mesenteric bypass is provision of inflow from a healthy supraceliac aorta; however, it typically requires complete occlusion of the supraceliac aorta during construction of the proximal anastomosis, which may increase the hemodynamic and ischemic intestinal demands experienced by the patient. Adequate exposure of supraceliac aorta is required for antegrade reconstruction, with care taken to identify and protect the esophagus. In addition, while creating the retropancreatic tunnel, care is needed to prevent injury to the splenic vein.

●Retrograde bypass to the SMA is easier to create and usually performed more quickly than antegrade bypass; however, retrograde bypasses are prone to kinking, which can be reduced by using an externally supported prosthetic graft. Kinking can also be prevented by placement of the bypass graft in a "gentle reverse C" configuration.

For celiac revascularization, the distal bypass target is either the celiac trunk or the common hepatic artery. The celiac trunk allows for an end-to-end anastomosis, while the hepatic artery allows for easier exposure, but makes orientation of the graft more difficult. These bypasses usually arise from the supraceliac aorta directly given the lack of calcification usually found in this area and the fact it is exposed when exposing the celiac trunk.

For superior mesenteric revascularization, the anastomosis is usually placed just distal to the origin of the middle colic artery where the artery is soft and free of disease with multiple distal branches by which to perfuse the intestines.

Conduit selection — Either autogenous vein or prosthetic (eg, polyester or polytetrafluoroethylene [PTFE]) graft can be used as a conduit for mesenteric bypass. Data are conflicting about which conduit is better. Most studies suggest there is no clinically significant difference in outcomes between the different types [31-33].

For autogenous conduit, saphenous or femoral vein can be used; however, dissection of the femoral vein increases the time and complexity of the bypass. The main issue with using vein is the risk of kinking. This can be addressed using an externally supported prosthetic graft, provided there is no gross contamination of the operative field (ie, spillage of intestinal contents, pus). In addition to vein, cryopreserved vessels can also be used as a bypass conduit in contaminated fields.

Antegrade mesenteric bypass — Antegrade mesenteric bypass provides a shorter bypass and more robust inflow to the bypass. It also has a reduced incidence of kinking due the shorter length bypass. However, more time is needed to achieve exposure, and placement of the supraceliac aortic clamp increases the physiologic stresses on the patient. This approach should be avoided in patients with severe coronary heart disease or history of heart failure.

Adequate exposure of the supraceliac aorta is required for antegrade reconstruction, with care taken to identify and protect the esophagus. The supraceliac aorta can be approached through either a midline or bilateral subcostal incision. The midline incision is easier to close, while a bilateral subcostal incision can help with exposure of the upper abdomen in larger patients.

The triangular ligament of the liver is divided, with care taken to identify and avoid injury to the inferior vena cava and hepatic veins, and the left lateral segment of the liver is moved laterally. The gastrohepatic ligament is then divided, with care to avoid injury to a replaced left hepatic artery, which if present would course through the ligament. Knowledge of visceral vessel configurations is important to ensure that aberrant vessels are identified and preserved. (See 'Mesenteric anatomy and targets for revascularization' above.)

The esophagus and stomach are then mobilized laterally. The median arcuate ligament and the crura of the diaphragm are divided. The posterior peritoneum is divided, and the aorta is exposed. The aorta does not need to be dissected circumferentially, but enough exposure is needed to clamp proximal to site of anastomosis.

●For celiac revascularization, the celiac trunk is exposed by dividing the overlying crural fibers, or the common hepatic artery can be exposed along the lesser curve of the stomach in the porta hepatis.

●For mesenteric revascularization, the SMA is exposed either in the lesser sac at the base of the pancreas, at the base of the transverse colon mesentery, or laterally after mobilization of the fourth portion of the duodenum. The decision on which area to expose depends on the location of the disease being treated. A retropancreatic tunnel for the graft is created using gentle finger dissection, with care to prevent injury to the splenic vein.

After the patient has been adequately anticoagulated (typically using unfractionated heparin), the proximal and distal anastomoses are created with the celiac artery anastomosis performed first, followed by the SMA anastomosis. The anastomoses are back bled and flushed prior to completion. The retroperitoneal tissue is then reapproximated over the graft with absorbable suture.

Retrograde mesenteric bypass — A retrograde bypass can be performed more quickly than an antegrade bypass. This allows for more rapid revascularization, which can be important for preserving bowel length. The infrarenal aorta, right common iliac, or left common iliac artery can be used as inflow, depending on the extent and severity of atherosclerosis. For retrograde mesenteric bypass, a lateral approach to exposing the SMA allows the anastomosis to lay in a less oblique angle to help minimize kinking.

After the patient has been adequately anticoagulated (typically using unfractionated heparin), the proximal anastomosis to the SMA is performed, and the graft is tunneled in a gentle curve, reverse C loop from posterior to anterior, with care to ensure the graft does not kink. The distal graft is trimmed for length, and the distal anastomosis is performed. The anastomoses are back bled and flushed prior to completion.

Transaortic endarterectomy — The use of transaortic endarterectomy is rarely indicated. It is often reserved for patients who have previous abdominal radiation, extensive abdominal wall hernia, hostile abdomen, or failed endovascular attempts with bacterial contamination or perforated bowel.

The aorta is approached through a retroperitoneal incision, which allows for treatment without entering the abdominal cavity. The aorta is exposed from the supraceliac to the infrarenal aorta, with care taken to not injure the left renal vein as it crosses the aorta.

Once proximal and distal control of the aorta are obtained, the patient is anticoagulated (typically using unfractionated heparin), and a trapdoor incision is made in the visceral segment of the aorta to allow for endarterectomy of the aorta and eversion endarterectomy of the celiac artery and SMA. The trapdoor incision is closed with 3-0 Prolene sutures.

Adjunctive procedures

Bowel evaluation and resection — After revascularization, it is often hard to predict based on the appearance of the bowel whether it will progress to frank necrosis.

While many techniques have been described to help determine the viability of the remaining bowel intraoperatively including observation for peristaltic movements, Doppler examination, fluorescein, perfusion fluorometers, indocyanine green, and tissue oxygenation, none of these is perfect in predicting viability. It is often just time that is needed to allow viable bowel to demarcate.

Given this, bowel resection in the operating room and in the immediate postoperative period should be limited to perforated or frankly necrotic bowel to preserve bowel length using a damage control approach. Limiting the amount of initial resection and any subsequent resections also helps avoid short gut syndrome. (See "Bowel resection techniques" and "Acute mesenteric arterial occlusion", section on 'Short bowel syndrome'.)

Second-look laparotomy — Re-exploration should be used liberally in patients with severe chronic mesenteric ischemia and acute mesenteric ischemia. A "second-look" laparotomy is helpful to manage bowel necrosis in the immediate postoperative period and also helps to avoid confusion with early graft thrombosis, sepsis, or need for further resuscitation. It is generally unwise to proceed with bowel anastomosis if additional bowel resection is required at the second look. Bowel anastomosis should only be completed at the time of exploration if all remaining bowel appears viable to reduce the risk of anastomotic failure.

Temporary abdominal closure is frequently performed to allow for subsequent return to the operating room to assess bowel viability and perform limited resections with less impact. Issues regarding management of patients with an open abdomen and timing of abdominal closure are reviewed separately. (See "Management of the open abdomen in adults".)

POSTOPERATIVE CARE AND SURVEILLANCE

Postoperative course — The postoperative course varies depending on the clinical presentation of ischemia, the nature of revascularization, and patient factors.

After mesenteric stenting, patients with chronic mesenteric ischemia are usually admitted for overnight observation, but increasingly these patients are being treated in the outpatient setting, particularly if they are mildly symptomatic. Diet is resumed six to eight hours after the procedure, and the patient is placed on antiplatelet therapy for life. Clopidogrel is provided the day of procedure and continued for one to three months, but there is no consensus on the optimal duration [34]. (See 'Postoperative care and surveillance' above.)

Following open mesenteric revascularization for acute or chronic mesenteric ischemia, patients are often very ill and are admitted to the intensive care unit for hemodynamic and nutrition support, as needed. Those with severe intestinal ischemia frequently develop major fluid shifts and lose autoregulation of the intestines and are at risk for abdominal compartment syndrome, which reduces bowel perfusion and increases the rate of graft occlusion. Temporary abdominal closure is often used to avoid this complication. (See "Abdominal compartment syndrome in adults" and "Management of the open abdomen in adults".)

Patients who are treated for chronic mesenteric ischemia often have long-standing food fear and may additionally require nutrition support until that behavior resolves. Absorption capacity often changes due to ischemic changes, and diarrhea with coexisting fluid losses can persist for a few weeks following revascularization. (See "Overview of perioperative nutrition support", section on 'Postoperative nutrition support'.)

Postoperative imaging and surveillance

●Mesenteric stenting – Following mesenteric stenting, early duplex imaging (within 1 month) is advocated following mesenteric stenting to set a new baseline because velocities are increased in stented vessels, with a few studies suggesting new criteria for in-stent stenosis [35-37]. Duplex surveillance should be repeated at six-month intervals for the first year and then annually thereafter, provided there is no evidence for restenosis. Repeat imaging and possibly reintervention is indicated for return of symptoms and/or evidence of re-stenosis based on increase velocities. While there are currently no validated velocities to define in-stent restenosis, some criteria have been suggested. Peak systolic velocities >445 cm/sec have the highest sensitivity and specificity for superior mesenteric artery in-stent stenosis, and velocities >289 cm/sec have the highest sensitivities and specificities for celiac artery in-stent restenosis [35].

●Mesenteric bypass – Following mesenteric bypass, the graft should be evaluated with computed tomographic angiography or mesenteric duplex prior to discharge. The patient is followed clinically in the postoperative period until issues have resolved. Graft surveillance continues at six-month intervals using duplex ultrasound.

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Intestinal ischemia" and "Society guideline links: Occlusive carotid, aortic, renal, mesenteric, and peripheral atherosclerotic disease".)

SUMMARY AND RECOMMENDATIONS

●Mesenteric ischemia – Mesenteric ischemia can be due to a variety of etiologies that reduce perfusion to the intestines, affecting any combination of the celiac axis, the superior mesenteric artery (SMA), or the inferior mesenteric artery. The clinical presentation may be acute or chronic. (See 'Introduction' above and 'Indications and technique selection' above.)

●Mesenteric revascularization – Techniques for mesenteric revascularization include percutaneous angioplasty/stenting, open surgical revascularization (eg, mesenteric bypass, endarterectomy), and hybrid approaches (eg, retrograde open mesenteric stenting [ROMS]). The timing and technique chosen are based on acuity of the presentation (acute, chronic), lesion characteristics, and patient-related factors. (See 'Indications and technique selection' above.)

●Acute mesenteric ischemia – For patients with acute mesenteric ischemia, together with resuscitation and systemic anticoagulation, mesenteric revascularization should be performed expeditiously to optimize patient outcomes. Rapid restoration of flow and the ability to assess the intestines for irreversible ischemia favors open surgical techniques. However, in selected patients, a percutaneous endovascular approach (eg, pharmacomechanical thrombolysis) may be an alternative; laparotomy may still be required to manage the bowel. (See 'Acute mesenteric ischemia' above.)

•Embolic occlusion – Open embolectomy is preferred to percutaneous techniques for patients with acute mesenteric ischemia due to embolism. SMA embolectomy is a relatively straightforward procedure to perform that rapidly restores blood flow. (See 'Acute mesenteric ischemia' above and 'Superior mesenteric artery embolectomy' above.)

•Thrombotic occlusion – ROMS is preferred to open surgical bypass for patients with acute-on-chronic mesenteric ischemia. ROMS provides the benefits of exploratory laparotomy and effectively manages the atherosclerotic lesion with lower morbidity compared with open surgical bypass. (See 'Acute mesenteric ischemia' above and 'Retrograde open mesenteric stenting' above.)

•Bowel exploration – For patients with acute or acute-on-chronic mesenteric ischemia, evaluation of the entire length of bowel is necessary and easily accomplished during laparotomy, but laparoscopic exploration may also be an option. Only necrotic or perforated bowel is resected; the remaining bowel is allowed to recover and re-evaluated during a second-look operation. (See 'Adjunctive procedures' above.)

●Chronic mesenteric ischemia – For patients with symptomatic chronic mesenteric ischemia, revascularization should be performed only after exclusion of other possible causes for the patient's abdominal complaints. (See 'Chronic mesenteric ischemia' above.)

•Endovascular first approach – Initial endovascular revascularization is preferred to open surgical bypass for patients with chronic mesenteric ischemia and suitable vascular anatomy. Perioperative complication rates are lower for endovascular techniques; however, endovascular revascularization is less durable, and repeat intervention may be necessary. Revascularization of the SMA with angioplasty and stenting is the main goal; celiac artery revascularization is a secondary goal. Following mesenteric stenting, dual antiplatelet therapy is initiated and continued for one to three months, followed by aspirin therapy indefinitely.

-We suggest using a covered stent, rather than angioplasty alone or using an uncovered stent for treatment of the SMA (Grade 2C). Restenosis rates are lower for covered compared with uncovered stents. During mesenteric angioplasty and stenting, using embolic protection devices reduces the risk of distal embolization. (See 'Endovascular techniques' above.)

-For patients with chronic lesions that are not expected to be successfully treated with percutaneous approach (eg, flush occlusion, long segment disease, excessive calcification, access vessel disease/occlusion) or in whom prior angioplasty/stenting has failed, ROMS is an alternative endovascular technique for good-risk surgical candidates. (See 'Retrograde open mesenteric stenting' above.)

•Open surgical revascularization – If mesenteric angioplasty/stenting is not an option, open mesenteric bypass provides a durable revascularization for good-risk surgical candidates. Major complication rates and long-term outcomes are similar for the various approaches for open surgical bypass (eg, antegrade versus retrograde bypass, type of conduit). Selection is influenced by urgency, anatomy, suitability of vessels for clamping, and autogenous conduit availability and quality. (See 'Mesenteric artery bypass' above.)

●Postoperative surveillance – Following revascularization for acute or chronic mesenteric ischemia, all patients should be followed clinically until gastrointestinal issues have resolved and periodically thereafter for return of symptoms that may necessitate repeat intervention. (See 'Postoperative imaging and surveillance' above.)

•After mesenteric bypass, the graft should be evaluated with computed tomographic angiography or mesenteric duplex prior to discharge. Graft surveillance continues at six-month intervals using duplex ultrasound.

•After mesenteric stenting, duplex surveillance is obtained early in the postprocedure period, at six months, at one year, and annually thereafter. Further evaluation is indicated for a peak systolic velocity >445 cm/sec in the stented SMA or peak systolic velocity >289 cm/sec in the stented celiac artery.