Diagnosis and Management of Acute Mesenteric Ischemia

Educational Objectives

The goal of this program is to improve the diagnosis and management of acute mesenteric ischemia (AMI). After hearing and assimilating this program, the clinician will be better able to:

1. Distinguish among the various types of acute mesenteric ischemia.
2. Detect AMI using appropriate imaging modalities and diagnostic tools.
3. Assess for bowel necrosis using indocyanine green fluorescein angiography during elective or emergency surgery.
4. Utilize appropriate surgical techniques and tools in patients undergoing emergency abdominal surgery.

Summary

Mesenteric venous ischemia (MVI): caused by mesenteric venous thrombosis; incidence is <10%; occurs in patients with hypercoagulable states, paraneoplastic syndromes, and pancreatitis; may present with abdominal pain, tenderness, and peritonitis; computed tomography (CT) confirms the diagnosis; treatment is anticoagulation; investigate the cause for hypercoagulability; evidence of intestinal ischemia may warrant surgical intervention

Arterial acute mesenteric ischemia (MI; AMI): seen in most patients with AMI; classified into 3 groups

Mesenteric arterial embolism: occurs in patients with atrial fibrillation who have embolic ischemic events in the legs, brain, and mesenteric vasculature; occurs in ≈50% of AMI patients; source of embolus can be cardiac (common) or aortic, or via catheterization during angiography; often occurs at the origin of the middle colic artery (first major branch of the superior mesenteric artery [SMA], which branches from the aorta at a low angle); leads to ischemia of the right ascending and transverse colon supplied by SMA; treatment is embolectomy; presents with acute abdominal pain (abdomen may be tender on physical examination [PE]); pain is out of proportion to PE; findings may be benign initially, as ischemia may not be transmural to produce peritonitis; laboratory workup and CT may establish diagnosis

Occlusive MI: occurs in patients with preexisting atherosclerotic occlusive disease in mesenteric circulation and other regions (eg, limb claudication, coronary atherosclerosis, cerebrovascular atherosclerosis); some patients have symptomatic chronic arterial MI; thrombosis of the narrowed mesenteric circulation leads to sudden intestinal ischemia; involves generalized multivessel disease, as the gastrointestinal tract receives blood supply from 3 major arteries (eg, foregut receives dual blood supply from coeliac artery and SMA); involves >1 significantly diseased vessel of the mesenteric circulation; patients with preexisting occlusive disease present with acute abdominal pain that may be out of proportion to PE; CT usually reveals many occluded vessels

Nonocclusive MI: occurs in patients who do not have preexisting atherosclerotic vascular disease but are dehydrated and have low cardiac output states (eg, sepsis, on vasopressors); mesenteric vasoconstriction may occur because of dehydration, leading to MI

Computed tomography: immediate CT of a poorly perfused bowel may not show abnormal findings, but this does not rule out necrotic bowel (NB); abdominal CT is 95% sensitive; presentation with symptoms suggestive of NB warrants a high index of suspicion even with a negative CT finding; pneumatosis intestinalis (PI) — air in the bowel wall (BW) is seen on CT below a column of fluid; may also be associated with air in the portal venous system (portal venous gas [PVG]); gas-forming bacteria invading through the BW is associated with loss of BW integrity and evolving ischemic necrosis

Diagnosis: abdominal pain, tenderness, and laboratory findings (eg, acidosis) confirm diagnosis of intestinal ischemia; PI and PVG (less common) can be incidental and benign findings in an otherwise asymptomatic patient, eg, during surveillance CT for cancer; abnormal history or physical or laboratory findings (eg, anemia, peritonitis, abnormal lactate, elevated international normalized ratio) indicate nonbenign PI; PI in addition to other CT findings (eg, free fluid in the abdomen and ileus) or involvement of the small bowel is not benign

Key principles of management: include timely diagnosis, restoration of blood flow as early as possible, and removal of nonviable bowel (non-VB) while preserving VB; CT angiography (CTA) of the abdomen may help vascular surgeons restore blood flow via open surgery or catheter-based intervention; presence of peritonitis may indicate non-VB, but its absence does not rule out necrosed bowel; CT findings may strongly suggest ischemia or necrosis, but a normal CT does not rule out non-VB; intraoperative assessment of bowel viability by fluorescein angiography (FA) can be useful; preoperative assessment of bowel viability is challenging in the context of MI

The American Association for the Surgery of Trauma (AAST): developed a scoring system for 16 emergency general surgery (EGS) diagnoses as well as other organ injuries (eg, spleen, liver, brain, fractures); the AAST grading system for AMI is based on clinical, operative, radiologic, and pathologic criteria; the speaker and his colleagues evaluated whether AAST grading system for AMI can help predict the need for surgery; clinical criteria for AMI — grade 1 is anorexia and abdominal pain; grade 2 is abdominal pain out of proportion to PE, but no peritonitis; grade 3 is abdominal pain and tenderness without peritonitis; grades 4 and 5 include abdominal pain and tenderness with peritonitis; when the AAST clinical grading scale was applied retrospectively to patients with AMI, ≥60% of patients encompassing all grades required an operative procedure and ≥40% required bowel resection (BR); no clinical grades for AMI rule out the possibility of bowel necrosis and need for BR

CT in the diagnosis of AMI: diagnosis of AMI relies heavily on CT; specificity of CT for AMI is ≈95%; clear evidence of ischemia on CT indicates a high probability of detection during surgery; in intestinal ischemia, positive findings on CT are highly likely but not always seen; PI or PVG on CT increases the probability of AMI; consulting a surgeon is recommended; surgeons are encouraged toward surgical intervention (open surgery or laparoscopy)

Operative intervention: establishing blood flow — priority; obtain CTA and consult a vascular surgeon to improve blood flow if possible (often catheter-based); resect non-VB, with a plan to return; postoperative critical care — essential; avoid vasopressors; good distention of terminal arterioles by volume loading is recommended to correct microvascular ischemia; in surgery — NB can be detected by bowel discoloration, peristalsis, pulsations in the root of mesentery, or Doppler signals at the margin of the mesentery; attenuation of the ischemic BW develops very distinct folds; bowel that folds like paper is likely necrotic; bleeding upon grasping, incising, or amputating a small segment of bowel indicates viability; continue amputating the segment of bowel until bleeding occurs, then staple the bowel and close the abdomen; perform second-look (SL) operation the next day

Assessment of bowel necrosis: extensive resection of bowel should be avoided, however, leaving NB in the abdomen can perpetuate shock and sepsis, leading to hemodynamic compromise, which can increase risk for further bowel necrosis; fluorescein — may be better than Doppler or PE; can prevent resection of VB, which lights up under the lamp; not used as often as indocyanine green FA (ICG-FA; eg, SPY system); ICG-FA is used in elective surgery (eg, colorectal surgery) to clearly demarcate viable tissue; studies show potentially good results with use of ICG-FA in emergency surgery; relatively unproven in emergency surgery diagnoses (eg, acute intestinal ischemia) but may be worth considering

SL laparotomy: Hansraj et al (2019) — examined the rate of BR in patients undergoing first or SL laparotomy, or both; BR was performed in ≈60% of patients, ≈33% of whom underwent BR during the SL procedure; 4 resections were performed only during the SL procedure, which may be because of uncertainty about the viability of the bowel or the extent of BR needed during the first operation; a clear picture may emerge during the SL procedure, which remains a valid technique

Stapling vs sewing technique: Bruns et al (2017) — prospectively evaluated stapling vs sewing technique in patients undergoing emergency abdominal surgery requiring BR; overall, mortality rate was ≈7%; anastomotic leak developed in 12.5% of patients (higher proportion compared with elective surgery); failure rate was similar in stapled vs hand-sewn group; the hand-sewn group was relatively sicker; contamination and open abdomen contribute to anastomotic failure, ie, rapid closure of the abdominal wall is essential; Hernandez MC et al (2018) — evaluated association of AAST EGS grading with hand-sewn vs stapled anastomosis; mortality rate was not associated with AAST grading or anastomotic technique but with anastomotic failure or vasopressor use

Temporary abdominal closure: a classic approach is to use a Bogota bag; Barker Vacuum Pack — inexpensive; involves use of a plastic cover to protect the viscera, with a blue towel on top; fluid can leak out through the openings in the plastic sheet and get sucked through the towel; drains on the margins of the towel at the skin edge and an antimicrobial drape (eg, Ioban) complete the temporary closure; open abdomen dressing (ABTHERA) — has long suction arms into the gutters; valuable and helpful when suction is required in the gutters; Wittmann Patch — another option; ideal choice — an easy, inexpensive technique that protects the bowel and allows easy access for a relook

Extensive intestinal ischemia: global necrosis of the intestine is no longer considered nonsalvageable; one approach is to remove all the necrotic intestine and direct the gastrointestinal tract out to the skin; this is generally the duodenum as the small bowel becomes necrotic at the ligament of Treitz; after closure of the abdomen, the patient receives total parenteral nutrition and is referred to a small-bowel transplant center; the speaker prefers this approach in patients who do not have multiple organ failure, specifically young and otherwise healthy patients (eg, trauma, postpartum cardiomyopathy) who have global intestinal ischemia

Recommendations: use of antibiotics is appropriate as the patient may be septic and in shock; consider heparin administration

Readings

Acosta S. Mesenteric ischemia. Curr Opin Crit Care. 2015; 21(2):171-178. doi:10.1097/MCC.0000000000000189; Аlexander K, Ismail M, Alexander M, et al. Use of ICG imaging to confirm bowel viability after upper mesenteric stenting in patient with acute mesenteric ischemia: Case report. Int J Surg Case Rep. 2019;61:322-326. doi:10.1016/j.ijscr.2019.07.077; Bala M, Kashuk J, Moore EE, et al. Acute mesenteric ischemia: guidelines of the World Society of Emergency Surgery. World J Emerg Surg. 2017; 12:38. Published 2017 Aug 7. doi:10.1186/s13017-017-0150-5; Bruns BR, Morris DS, Zielinski M, et al. Stapled versus hand-sewn: A prospective emergency surgery study. An American Association for the Surgery of Trauma multi-institutional study. J Trauma Acute Care Surg. 2017; 82(3):435-443. doi:10.1097/TA.0000000000001354; Ehlert BA. Acute gut ischemia. Surg Clin North Am. 2018; 98(5):995-1004. doi:10.1016/j.suc.2018.06.002; Gnanapandithan K, Feuerstadt P. Review article: Mesenteric ischemia. Curr Gastroenterol Rep. 2020; 22(4):17. Published 2020 Mar 17. doi:10.1007/s11894-020-0754-x; Hansraj N, Pasley AM, Pasley JD, et al. “Second-look” laparotomy: warranted, or contributor to excessive open abdomens? Eur J Trauma Emerg Surg. 2019; 45(4):705-711. doi:10.1007/s00068-018-0968-x; Hernandez MC, Bruns BR, Haddad NN, et al. RESHAPES: Increasing AAST EGS grade is associated with anastomosis type. J Trauma Acute Care Surg. 2018; 84(6):855-863. doi:10.1097/TA.0000000000001864; Olson MC, Fletcher JG, Nagpal P, et al. Mesenteric ischemia: what the radiologist needs to know. Cardiovasc Diagn Ther. 2019;9(Suppl 1):S74-S87. doi:10.21037/cdt.2018.09.06; Reintam Blaser A, Acosta S, Arabi YM. A clinical approach to acute mesenteric ischemia. Curr Opin Crit Care. 2021; 27(2):183-192. doi:10.1097/MCC.0000000000000802; Sindall ME, Davenport DL, Wallace P, et al. Validation of the American Association for the Surgery of Trauma grading system for acute mesenteric ischemia-More than anatomic severity is needed to determine risk of mortality. J Trauma Acute Care Surg. 2020; 88(5):671-676. doi:10.1097/TA.0000000000002592; Tominaga GT, Staudenmayer KL, Shafi S, et al. The American Association for the Surgery of Trauma grading scale for 16 emergency general surgery conditions: Disease-specific criteria characterizing anatomic severity grading. J Trauma Acute Care Surg. 2016; 81(3):593-602. doi:10.1097/TA.0000000000001127.

Disclosures

For this program, members of the faculty and planning committee reported nothing relevant to disclose.

Acknowledgements

Dr. Bernard was recorded exclusively for Audio Digest. Audio Digest thanks the speakers and the New York Society for Gastrointestinal Endoscopy for their cooperation in the production of this program.

ABS Continuous Certification

Successful completion of this CME activity, which includes participation in the evaluation component, enables the learner to earn credit/s toward the CME [and Self-Assessment] requirements of the American Board of Surgery’s Continuous Certification pro

CME/CE INFO

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Lecture ID:

GS690901

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