Contemporary Management of Acute Mesenteric Ischemia in the Endovascular Era

Laboratory Test

In acute mesenteric ischemia, leukocytosis and elevated lactate levels often present. Partial- or full-thickness bowel necrosis allows bacterial translocation and subsequent leukocytosis. Increased immature white blood cells may present. As the disease progresses in severity, metabolic acidosis and signs of shock may follow. ¹⁰

Imaging Study

When hemodynamically stable, duplex ultrasonography remains an excellent tool to identify mesenteric disease, as it avoids contrast and radiation while maintaining a sensitivity of 70% to 90%. ¹¹ Established criteria for >70% stenosis include poststenotic turbulence with a fasting peak systolic velocity greater than 275 cm/s (superior mesenteric artery [SMA]) or 200 cm/s (celiac artery [CA]). ¹² Shortcomings include poor visualization with rapid breathing, obese body habitus, recent intra-abdominal surgery, or bowel gas. Also, ultrasound often has difficult visualization of distal arterial emboli or the inferior mesenteric artery (IMA). Given the shortcomings, ultrasound has limited utility for diagnosis of acute mesenteric pathology and interventional planning.

Computed tomography (CT) angiography is the recommended first step for evaluating intestinal vasculature in the acute setting with a sensitivity of 96% and specificity of 94%. ¹³ In addition to allowing identification of visceral arterial pathology, CT allows evaluation of nonvascular findings of the disease process, such as bowel wall thickening, dilatation, mesenteric fat stranding, pneumatosis, and portal venous gas ¹³ (Figures 1 and 2). MVT may need to adjust timing of the contrast to enhance visceral venous system. The CT is also rapid, noninvasive, and widely available in most hospitals. Findings of CT angiography and sensitivity/specificity of the acute mesenteric stenosis are summarized in Table 2.

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Figure 1.

Pneumatosis intestinalis on the CT. CT indicates computed tomography.

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Figure 2.

Portal venous gas on the CT. CT indicates computed tomography.

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Table 2.

Analysis of CT Findings.

Findings	Acute MI, n = 26	Control, n = 36	Sensitivity (%)	Specificity (%)
Pneumatosis intestinalis	11	0	42	100
SMA or combined CA and IMA occlusion	5	0	19	100
Arterial embolism	3	0	12	100
SMA or portal venous gas	3	0	12	100
Focal lack of bowel wall enhancement	11	1	42	97
Free intraperitoneal air	5	2	19	94
SMA or portal venous thrombosis	4	2	15	94
Solid organ infarction	4	2	15	94
Bowel obstruction	3	2	12	94
Bowel dilatation	17	6	65	83
Mucosal enhancement	12	7	46	81
Bowel wall thickening	22	10	85	72
Mesenteric stranding	23	14	88	61
Ascites	19	24	73	33

Abbreviations: CA, celiac artery; CT; computed tomography; IMA, inferior mesenteric artery; MI, myocardial infarction; SMA, superior mesenteric artery.

Source: From Kirkpatrick ID, et al: Biphasic CT with mesenteric CT angiography in the evaluation of acute mesenteric ischemia: initial experience. Radiology. 2003; 229(1):91-98.

Magnetic resonance imaging (MRI) can be a useful adjunct when the patient or clinician prefers to avoid CT radiation exposure or history of contrast allergy or intrinsic renal disease prohibit contrast for CT. Although MRI with gadolinium may also cause nephrogenic systemic fibrosis, MRA using time of flight does allow angiographic imaging without gadolinium. In the chronic setting, it has a sensitivity of 100% and a specificity of 95% when used with contrast gadolinium, ¹⁴ but this is significantly lowered without contrast and often overestimates the degree of disease. ⁹ Its disadvantages include long acquisition time, poor visualization of distal arterial disease, and poor visualization of the IMA. The MRI is also contraindicated in patient with metallic implant such as cardiac defibrillator or pacemaker.

Diagnostic angiography was once the gold standard but now is only used when a therapeutic intervention is planned. Carbon dioxide (CO₂) arteriography can be an adjunct to reduce or even eliminate contrast administration and mitigate contrast-induced nephropathy. Plain film radiographs have little role in the diagnosis of mesenteric ischemia with poor sensitivity and specificity. However, findings of pneumatosis intestinalis or portal venous gas may suggest advanced mesenteric disease (Figure 3).

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Figure 3.

Pneumatosis intestinalis on plain abdominal x-ray.

Embolism

Acute mesenteric ischemia is most commonly caused by acute arterial embolization (40%-50%), but the increasing emphasis on anticoagulation for atrial fibrillation and novel anticoagulants may be decreasing embolic phenomena. ^15,16 Classically, a patient in atrial fibrillation without therapeutic anticoagulation develops an embolus to the SMA just distal to the origin of the middle colic artery. The SMA is more often involved than the celiac axis or IMA due to its less acute angle of takeoff from the aorta as well as its larger caliber. Since the SMA decreases in caliber with the takeoff of the early branches (pancreaticoduodenal artery, jejunal, and middle colic artery), most emboli lodge near or just beyond the origin of the first jejunal branch, causing ischemia from the jejunum to the ascending colon. In addition to atrial fibrillation, other cardiac arrhythmias, structural heart defects, mural thrombus after myocardial infarction, and thoracic aorta atherosclerotic plaque are potential sources of emboli. Given the lack of robust collateral arterial splanchnic circulation, these patients with SMA embolus rapidly progress in severity and often with infarcted small and large bowel. In contrast, acute embolus to the celiac or IMA alone may be better tolerated with a more insidious presentation.

Thrombosis

Acute thrombosis of mesenteric arterial inflow (20%-30%) is increasing in frequency coupled with similarly high mortality (mostly 70%-100%). ¹⁷ Acute thrombosis often occurs in the elderly patients with atherosclerotic risk factors who at baseline already have preexisting mesenteric stenoses or occlusions. Acute mesenteric thrombosis usually develops at a chronic atherosclerotic lesion at the origin, a spillover lesion from the aorta which exacerbates the ischemia from other already occluded mesenteric vessels. This more proximal occlusion of greater numbers of mesenteric vessels often results in greater bowel involvement in the acute setting than embolization. Unfortunately, many patients with acute thrombosis also detail a history of symptomatic chronic mesenteric ischemia that often was not realized or addressed.

Initial Treatment

On initial presentation, if acute mesenteric ischemia due to acute emboli or acute thrombosis is suspected, one must expeditiously obtain laboratory and radiographic testing while simultaneously preparing for urgent surgical intervention. Medical management includes fluid resuscitation, antibiotic coverage, and therapeutic anticoagulation. Visceral necrosis induces profound systemic inflammatory responses and rapidly progress to shock and multiorgan system failure. Increased capillary permeability leads to acute fluid shift and subsequent hemodynamic instability. Thus, invasive hemodynamic monitoring may be necessary, and prompt crystalloid or blood product infusion is essential to improve hemodynamic function. The fluid volume requirement can be very high, up to 10 to 20 L, during the first 24 hours after intervention. ¹⁵ Empiric broad-spectrum antibiotics covering gram-negative or anaerobic organism are also necessary due to bacterial and cellular toxin translocation through the damaged epithelial and endothelium of injured intestinal wall. ^18,19 Therapeutic anticoagulation is also employed to prevent further clot propagation. Unfractionated heparin anticoagulation may be useful in the acute setting, given the need to titrate and reverse anticoagulation in the setting of potential emergent surgical intervention.

Techniques of Operation

The gold standard of treatment is an open transperitoneal approach via full midline incision of the abdomen. However, minimally invasive laparoscopy can replace the role of laparotomy for initial evaluation. Current guidelines from the Society for American Gastrointestinal and Endoscopic Surgeons indicates laparoscopy can be safely used to find the source of illness for the patient in unexplained sepsis, systemic inflammatory response syndrome, and multisystem organ failure with abdominal pain or tenderness. ²⁰ After safely obtaining access to the abdomen, inspection should be performed from the distal esophagus to the rectum. Obviously necrotic bowel should be removed. However, marginal appearing bowel should be observed without resection until successful revascularization of the visceral vessel. Doppler signal or intravenous fluorescein with Wood’s lamp can help to determine viability of the bowel. However, with any questionable findings, it is recommended to perform a second-look laparotomy within 24 to 48 hours from the index operation to reassess bowel viability. Creation of an ostomy can also be considered when primary anastomosis is at high risk of leakage. These circumstances include poor blood supply to the anastomosis, hemodynamic instability, anastomosis at infected/inflamed area, and low pelvic anastomosis. Ostomy also allows easier accessibility to the intestinal viability and evaluation at bedside with prevention of catastrophic consequences if bowel anastomosis is disrupted.

Open Thromboembolectomy

After confirmation of location of the lesion, a transverse arteriotomy is made. Then, a balloon-tipped embolectomy catheter is advanced proximally and distally. Care must be taken not to overinflate the catheter which might cause intimal dissection. Then, the transverse incision is closed primarily using simple interrupted or running prolene sutures depending on the size of the vessel. With flow-limiting atherosclerosis, the incision can be elongated longitudinally, and an endarterectomy may be necessary. In this case, the incision should be closed using patchy angioplasty with autogenous vein or bovine pericardium patch to avoid risk of stenosis.

Open Bypass

Several combinations of bypass orientation and conduit are available. Historically, antegrade bypass has demonstrated efficacy and durability in acute mesenteric ischemia. Both CA and the SMA can be revascularized using bifurcated synthetic graft from the supraceliac aorta to the CA and SMA. However, patients with multiple cardiopulmonary and renal comorbidities may benefit from retrograde bypass from the iliac artery which can avoid aortic cross clamp. Inflow of the retrograde bypass can be iliac artery or infrarenal aorta. Both autogenous and prosthetic conduit can be used to construct a mesenteric bypass. Use of prosthetic conduit is contraindicated with intestinal perforation and obvious intestinal contamination. Saphenous vein or femoral vein can be utilized in this setting. Bowel infarction without gross enteric spillage and subsequent intestinal resection and reanastomosis remains unclear whether prosthetic conduit is ideal, but anecdotally this remains a viable option if the conduit is carefully protected.

Endovascular Therapy

Access to the SMA can be gained through antegrade brachial access or retrograde femoral approach. Femoral approach may need more manipulation to cannulate the SMA due to vessel’s acute downward angulation from the aorta. After successful access to the arterial system, systemic heparin (80-100 units/kg) is given with goal activated clotting time >200 seconds. Wires and catheters are used to cannulate the artery and cross the lesion for a pretreatment angiogram. If the degree of stenosis is uncertain, a mean pressure gradient can be obtained to confirm a hemodynamically significant (>15 mm Hg) lesion. Appropriate balloon angioplasty with or without stent placement is performed if indicated. Usually, 1-vessel intervention to the SMA is sufficient, given vigorous collaterals between CA and SMA, and between SMA and IMA, although the supporting data are lacking. There is one retrospective study that demonstrated multivessel revascularization does not confer better outcome compared to single-vessel revascularization in chronic mesenteric ischemia. ²¹

Outcomes of revascularization

The goal of the intervention is restoration of the visceral perfusion expeditiously. Like other vascular pathology, endovascular therapy is becoming more prevalent in acute mesenteric ischemia. ²² While randomized control trials comparing open versus endovascular revascularization do not exist, several single-center retrospective studies demonstrated favorable technical success rates and complication rates of endovascular revascularization in the treatment for acute mesenteric ischemia.

Ryer et al reviewed their experience in Mayo clinic from 1990 to 2010. ²³ The majority of the patients were arterial thrombosis (53%) or arterial embolism (31%); other etiologies also included bypass occlusion (13%), aortic dissection (2%), or in-stent occlusion (1%). They reported increased use of endovascular/hybrid revascularization in 2000s (17%) compared to 1990s (7%). However, the vast majority of patients (88%) still required open revascularization, including bypass (42%), embolectomy (40%), or endarterectomy (6%). Thirty-three patients (35%) required bowel resection at first-look operation. More than half (56%) of the patients underwent second-look operation, and one-quarter of them needed bowel resection at second look. Of the 11 endovascular patients, 7 required laparotomy and 5 required resection of necrotic bowel. Their 30-day and 1-year mortality was 22% and 40%, respectively. Major complications (cardiopulmonary, cerebrovascular, requirement of dialysis, and multiorgan failure) were 47%.

In a study from the University of Michigan, Arya et al reported 34 patients with acute mesenteric ischemia who were treated with endovascular (n = 11) and open (n = 23) revascularization techniques. ²⁴ This study did not identify etiology of each cohort. The baseline characteristics between the groups were slightly different: body mass index was higher in the endovascular group and a higher proportion of active smokers were in the open group. The report demonstrated similar bowel resection rate (36.4% in endovascular vs 43.5% in open), reexploration rate (63.6% in endovascular vs 56.5% in open), multisystem organ failure (27.3% in endovascular vs 8.7% in open), 30-day major morbidity (63.6% in endovascular vs 69.6% in open), and 30-day mortality (45.4% in endovascular vs 34.8% in open). None of these outcome variables were statistically different.

Arthur et al reviewed a 9-year experience in Cleveland Clinic from December 1999 to December 2008. ²⁵ Their data identified 70 patients with acute mesenteric ischemia secondary to thrombotic (65%) or embolic (35%) arterial occlusion. Endovascular therapy was employed in 56 (81%) patients and demonstrated acceptable technical success rate (87%). Preoperative comorbidities, white blood cell count, pH, aspartate transaminase, alanine transaminase, and lactate levels were similar between the endovascular first group and traditional open first group. However, the endovascular first approach demonstrated favorable postoperative morbidity variables over open conventional therapy: pulmonary insufficiency (27% vs 64%, P < .05), laparotomy (69% vs 100%, P < .05), and median length of bowel resection (52 cm vs 160 cm, P < .05). Mortality was similar between the groups (36% vs 50%, P = .15).

Advantages of an endovascular first approach are more prominent in a larger scale administrative database studies. Schermerhorn et al retrospectively mined the Nationwide Inpatient Sample from 1988 to 2006 and identified 5237 patients with acute mesenteric ischemia treated with percutaneous (n = 1857) or open surgical repair (n = 3380). They found that despite higher rates of cardiopulmonary comorbidities in the percutaneous group, in-hospital mortality (16% vs 39%, P < .01), length of stay (9 days vs 14 days, P < .01), and bowel resection (29% vs 47%, P < .01) were significantly lower with percutaneous intervention than open repair. ¹⁶ A recent study using the same database echoed these findings. Beaulieu et al identified 4665 patients who underwent intervention for acute mesenteric ischemia from 2005 through 2009. Of these, a total of 679 patients underwent revascularization, 514 (75.7%) patients underwent open revascularization and 165 (24.3%) patients underwent endovascular treatment. Severity of comorbidities in both the groups were similar, but overall mortality (24.9% vs 39.3%, P = .01), length of stay (12.9 days vs 17.1 days, P < .01), bowel resection (14.4% vs 33.4%, P < .01), and requirement total parenteral nutrition support (13.7% vs 24.4%, P < .01) were superior in endovascular group. A recent study from the American College of Surgeons National Surgical Outcome Improvement Program (NSQIP) identified 439 patients with acute mesenteric ischemia. This NSQIP study identified trends in the endovascular group toward lower transfusion requirement (3.7% vs 19.3%, P = .13), lower risk of postoperative pneumonia (22.2% vs 27.8%, P = .39), sepsis (25.9% vs 35.5%, P = .26) as well as a significant 2.5-fold decreased in mortality (P = .018). ²⁶ A study from the Europe using the Swedish Vascular Registry compared 42 endovascular interventions with 121 open interventions between 1999 and 2006 for acute mesenteric ischemia. They found that endovascular intervention demonstrated improved mortality at 30 days (28% vs 42%, P = .03) and 1 year (39% vs 58%, P = .02) and decreased rate of bowel resection and short bowel syndrome. ² These findings are summarized in Table 3.

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Table 3.

Summary of Recent Literatures (Results are Endovascular Versus Open Revascularization, Respectively).

Author (Year)	Data Source	Morbidity	Mortality
Schermerhorn et al (2009)	Nationwide Inpatient Sample	Length of stay: 9 days vs 14 days Bowel resection: 28% vs 37% Acute kidney injury: 11.4% vs 18.4% Cardiac complication: 2.1% vs 7.2% Respiratory complication: 1.1% vs 5.7%	In-hospital: 16% vs 39%
Block et al (2010)	Swedish Vascular Registry	Laparotomy: 55% vs 100% Bowel resection: 19% vs 63% Second-look operation: 31% vs 67% Short bowel syndrome: 27% vs 55%	30-day: 28% vs 42% 1 year: 39% vs 58%
Arthur et al (2011)	Single-Center Chart Review	Laparotomy: 69% vs 100% Bowel resection: 52 cm vs 160 cm	36% vs 50%
Beaulieu et al (2014)	Nationwide Inpatient Sample	Length of stay: 12.9 vs 17.1 days Bowel resection: 14.4% vs 33.4% TPN support: 13.7% vs 24.4%	In-hospital: 24.9% vs 39.3%
Branco et al (2015)	Nasional Surgical Quality Improvement Program	Transfusion: 3.7% vs 19.3% Pneumonia: 22.2% vs 27.8% Sepsis: 25.9% vs 35.5%	Odds ratio 0.4 (CI 0.2-0.9)
Arya et al (2016)	Single-Center Chart Review	Bowel resection: 36.4% vs 43.5% Sepsis: 45.4% vs 22.7% Re-exploration: 63.6% vs 56.5% Major morbidity: 63.6% vs 69.6%	30-day: 45.4% vs 34.8%

Abbreviations: CI, confidence interval; TPN, total parenteral nutrition.

The reason for differences between single-center retrospective study compared to the large administrative data study is unknown. The advantages of an endovascular approach over open revascularization may be not substantial enough to be detected in lower powered study. Another possibility is that administrative data cannot accurately identify the disease severity or timing of the diagnosis. Other than the study from Cleveland Clinic, none of the abovementioned studies identified disease severity at the time of intervention. Patients with advanced disease having ominous signs of peritonitis are often allocated into the open approach group. This is a limitation that a retrospectively designed study inevitably suffers. Selection and other bias in these studies highlight the need for definitive randomized prospective studies between endovascular and open mesenteric intervention.

Although endovascular repair for acute mesenteric ischemia demonstrated improved short-term mortality and morbidity, long-term experience in acute setting has not been accumulated. However, considering results of endovascular therapy in chronic mesenteric ischemia, visceral stenting/angioplasty may need diligent surveillance and follow-up interventions. Some studies have found relatively high early recurrence of symptoms and restenosis rates of 28% or greater at 2 years with endovascular repair. ²⁷ In contrast, some open repair series have reported immediate success rate of 100% and long-term, primary-assisted patency of open mesenteric repair as high as 79% at 9 years. ²⁸

Another shortcoming of endovascular therapy is lack of ability to assess intestinal viability. Multiple studies have shown that 14% to 59% of mesenteric ischemia ultimately required bowel resection ^16,22,25,26 ; thus, endovascular therapy alone mandates close observation of patients for potential development of peritonitis from bowel necrosis with prepare in need of emergent laparotomy and bowel resection. This may not amenable in hospitals with limited resources. ²⁹

In addition to the feared complication of death after open or endovascular repair, multiple other complications can occur. Acute renal failure is the leading morbidity occurring in 11.4% of acute mesenteric repair. Acute myocardial infarction is also unfortunately quite common with a prevalence of 5.0% after acute repair. Among these and other comorbidities, percutaneous intervention demonstrates significantly less overall complications (20% vs 38%) than open surgical mesenteric bypass. ²⁵ Bowel resection, in addition to age, congestive heart failure, and atrial fibrillation, were predictors of greater morbidity and mortality.

Mesenteric Venous Thrombosis

Mesenteric venous thrombosis is a rare but still lethal form of acute mesenteric ischemia. This mesenteric venous outflow obstruction causes massive bowel wall edema, influx of increased fluid into the bowel lumen, and ultimately compromises the ability of the intestinal capillaries to adequately provide oxygen to the intestinal mucosa. This disease often involves the superior mesenteric vein in 95% of cases and the inferior mesenteric vein in 5%. ³⁰ On examination, patients often demonstrate abdominal distension and guaiac-positive stools in addition to disproportionate abdominal pain. Intra-abdominal sepsis or catastrophe is a prevalent cause, but other risk factors include hypercoagulopathy such as activated protein C resistance, smoking, oral contraceptives, trauma, malignancy, pancreatitis, or liver cirrhosis (Table 1). Unlike acute mesenteric arterial ischemia, venous thrombosis often displays a delayed presentation. Acute MVT may present 24 to 72 hours after initial symptoms from thrombus formation, whereas subacute MVT may take several days to weeks. Chronic MVT can be asymptomatic and incidentally detected on radiographic study with findings of porto-MVT or consequences of portal hypertension: esophagogastric varices, splenomegaly, and ascites ³¹ (Figure 4).

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Figure 4.

Superior mesenteric vein and portal venous thrombosis with enlarged spleen. (White arrow: Thrombosis at the splenomesenteric confluence).

Management of MVT

Systemic therapeutic anticoagulation remains the standard initial treatment modality. Anticoagulation prevents progression of thrombosis while the body activates innate fibrinolysis and develops venous collateral outflow formation. Some studies have demonstrated reasonable outcomes with isolated systemic anticoagulation as the lone treatment of MVT. Acosta et al identified 51 patients with MVT, and 30-day mortality was 20%. ³² The same study demonstrated immediate use of therapeutic unfractionated heparin on diagnosis improves recurrence of thrombosis up to 12% and decreases mortality from recurrence by 37%. ³² A similar study of anticoagulation therapy found that 93% of patients treated with anticoagulation were recanalized the occluded veins. ³³ Although anticoagulation therapy is considered as the standard treatment of MVT, there is no established guideline for regiment, duration, and surveillance. Novel oral anticoagulants have yet to be studied in this disease entity. For long-term management, oral warfarin with goal international normalized ratio between 2.0 and 3.0 may be reasonable for a duration of 3 to 6 months for a patient with unprovoked thrombosis. Patients with underlying disorders often require extended treatment. Follow-up imaging may be necessary prior to cessation of treatment.

Utilization of catheter-directed thrombolytic therapy for MVT has increased in prevalence although there is no level 1 or strong level 2 evidence. Endovenous therapy can be delivered via variety of approaches, including transhepatic portovenous, transarterial through the SMA, and combined SMA and superior mesenteric vein. After the access has been established, various pharmacomechanical thrombolysis ± thrombectomy can be performed. Contemporary results of the endovascular therapy are promising. In China, Yang et al demonstrated 36 patients with acute MVT who were treated with a multidisciplinary stepwise approach which was defined as (1) systemic anticoagulation and intensive care, (2) endovenous therapy, and (3) damage control laparotomy, and ± second-look laparotomy. ³⁴ A 30-day mortality and recanalization rate were 11% and 91%, respectively. In a similar study from Italy, transhepatic portomesenteric thrombolysis and thrombectomy followed by systemic anticoagulation were used in 18 patients who were compared with 14 patients with isolated systemic anticoagulation therapy. In this study, thrombolysis group demonstrated 88% recanalization rate with a significant reduction in the rate of bowel resection rate (5% vs 35%, P < .05). ³⁵ In a smaller study from New York, 4 patients with acute MVT underwent endovascular thrombolysis, which resulted in 100% recanalization with freedom from the open operation. ³⁶ However, it should be noted that catheter-directed thrombolysis is contraindicated in a patient with recent stroke, recent trauma, cerebrospinal malignancy, or active bleeding. Even in patients without these conditions, up to 50% to 60%, adverse bleeding complication events were reported. ^37,38

Acute MVT with bowel necrosis mandates exploratory laparotomy. Open thrombectomy can be utilized at the time of laparotomy in whom venous revascularization is preferred. Klempnauer et al described concomitant splenic and superior mesenteric venous thrombectomy via transverse venotomy with bowel resection decreased mortality 22% compared to bowel resection alone. ³⁹ However, Hedayati et al found that majority of open venous thrombectomy were complicated by recurrent thrombosis in the immediate postoperative period. ⁴⁰

Recurrent thrombosis of the mesenteric vein is a dreadful consequence. This has been reported in 2% to 11%. This seems more common after cessation of anticoagulation therapy. A single-center retrospective study demonstrated 2.5% of recurrent MVT, recurrence occurred only after cessation of anticoagulation. ⁴¹ A large retrospective study using an international registry demonstrated a 7.3% recurrence rate during anticoagulation which became 10.5% after discontinuation of anticoagulation. ⁴²

Associated portal hypertension has been reported in 7% to 25%. ^36,43 It is unclear whether portal hypertension is a preceding condition and causes MVT or it is a long-term consequent complication from the MVT. Further study is necessary to elucidate what subset of patients are best suited for endovascular intervention and to minimize risk of recurrent MVT and portal hypertension.

Nonocclusive Mesenteric Ischemia

Even without arterial or venous mesenteric occlusion, mesenteric ischemia may still take place in underperfused states. Nonocclusive mesenteric ischemia occurs when splanchnic vasoconstriction causes inadequate microvascular blood flow to meet intestinal oxygen demand despite patent mesenteric vessels proximally. This often occurs in the elderly patients with low blood flow states, such as shock, heart failure, or drug-induced arterial vasospasm (vasopressor, cocaine, digitalis, and so on). Hypoperfusion of the mesentery has also been increasingly found in patients requiring hemodialysis for chronic renal failure or cardiac pump devices for low cardiac output. ^44,45 The ischemia is commonly widespread, affecting the bowel in a nonconsecutive manner. Nonoperative medical management with bowel rest and volume expansion with antibiotics are the standard of care for nonocclusive mesenteric ischemia.