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Mesenteric Vascular Insufficiency

Chapter 340 | Part 10: Disorders of the Gastrointestinal System · Part 10 – Gastrointestinal Disorders

Detailed clinical reference synthesised from Harrison's Principles of Internal Medicine, 22nd Edition

🔑 Key Clinical Points

  1. Pain out of proportion to physical examination is the hallmark clinical feature of acute mesenteric ischemia.
  2. Griffiths' and Sudeck's points are watershed areas within the colonic blood supply and common locations for ischemia.
  3. Mortality with acute mesenteric ischemia presentation remains high, between 50 and 80%.
  4. A negative duplex scan virtually precludes the diagnosis of mesenteric ischemia.
  5. Chronic mesenteric ischemia (CMI) is secondary to atherosclerotic disease involving the superior mesenteric artery (SMA) and/or celiac artery.
  6. Acute mesenteric ischemia (AMI) is most associated with embolus to the mid to distal SMA (50% of cases).
  7. Mesenteric venous thrombosis accounts for <10% of cases and is generally precipitated by a hypercoagulable state.
  8. Nonocclusive mesenteric ischemia represents 20% of cases and is secondary to intestinal ischemia when subjected to acute hemodynamic instability.
  9. Timeliness of diagnosis and treatment is the most significant indicator of survival in acute intestinal ischemia.
  10. Retrograde open mesenteric stenting (ROMS) is a hybrid approach indicated when conventional endovascular or open surgical approaches are not feasible.

📑 Table of Contents

📋 Figures in This Chapter

# Type Description
1 🖼 Figure Mesenteric 340 is FIGURE 340-1 Blood supply to the intestines includes the...

1. DEFINITION & OVERVIEW

  • Intestinal ischemia occurs when splanchnic perfusion fails to meet the metabolic demands of the intestines, resulting in ischemic tissue injury.
  • Mesenteric ischemia affects 2–3 people per 100,000 with an increasing incidence in the aging population.
  • Intestinal ischemia is further classified into chronic mesenteric ischemia (CMI) and acute mesenteric ischemia (AMI).
  • CMI is the failure to achieve normal postprandial hyperemic intestinal blood flow.
  • AMI is the occurrence of an abrupt cessation of mesenteric blood flow, usually embolic or thrombotic in nature.
  • CMI is secondary to multiple major visceral arterio-occlusive disease with involvement of the superior mesenteric artery (SMA) most worrisome.
  • AMI is most associated with arterio-occlusive mesenteric ischemia, nonocclusive mesenteric ischemia, and mesenteric venous thrombosis.

1.1 Classification of Mesenteric Ischemia

  • Chronic Mesenteric Ischemia (CMI):
  • Failure to achieve normal postprandial hyperemic intestinal blood flow.
  • Occurs due to an imbalance between supply and demand of oxygen metabolites to the intestinal tract similar to cardiac angina.
  • Occurs due to significant atherosclerotic disease leading to the narrowing of the SMA and/or celiac artery origins.
  • Duration of symptoms is typically 6–12 months.
  • Physical examination will often reveal a malnourished patient with other manifestations of atherosclerosis.
  • Acute Mesenteric Ischemia (AMI):
  • Occurrence of an abrupt cessation of mesenteric blood flow.
  • Approximately 50% of AMI is due to embolus to the mid to distal SMA.
  • The embolus etiology includes atrial fibrillation, recent myocardial infarction, soft atherosclerotic plaque, infective endocarditis, valvular heart disease, and recent cardiac or vascular catheterization.
  • Approximately 25–30% of the cases are characterized by an acute-on-chronic thrombosis in patients with preexisting mesenteric atherosclerosis.
  • Thrombotic occlusion most commonly occurs at areas of severe atherosclerotic narrowing at the SMA and the celiac artery.
  • Nonocclusive Mesenteric Ischemia:
  • Represents 20% of the cases.
  • Secondary to intestinal ischemia when subjected to acute hemodynamic instability.
  • Patients above the age of 50, especially those with coexisting conditions like myocardial infarction, congestive heart failure, aortic insufficiency, and renal or liver disease, who are also undergoing cardiovascular surgery, face the highest risk.
  • Hypovolemia, shock, and use of vasoconstrictive agents (e.g., digoxin, α-adrenergic agonists, cocaine) can precipitate ischemia in these patients.
  • It is the most prevalent gastrointestinal disease complicating cardiovascular surgery.
  • Mesenteric Venous Thrombosis:
  • Accounts for <10% of cases.
  • Generally precipitated by a hypercoagulable state due to an underlying inherited disorder such as factor V Leiden, prothrombin mutation, protein S deficiency, protein C deficiency, antithrombin deficiency, and antiphospholipid syndrome.
  • May also occur as a result of acquired thrombophilia in malignancies, hematologic disorders, and use of oral contraceptives.
  • Chronic diarrhea may also be noted.

2. EPIDEMIOLOGY

  • Incidence: 2–3 people per 100,000.
  • Trend: Increasing incidence in the aging population.
  • Mortality: Remains high (between 50 and 80%) with acute presentation.
  • Risk Factors:
  • Modifiable: Smoking, hypercoagulable states, cardiovascular disease.
  • Non-modifiable: Aging, atherosclerosis, atrial fibrillation.

3. ETIOLOGY & PATHOPHYSIOLOGY

  • Anatomy:
  • The blood supply to the intestines is supplied by the celiac artery, SMA, and inferior mesenteric artery (IMA).
  • Extensive collateralization occurs between major mesenteric trunks and branches of the mesenteric arcades.
  • Collateral vessels within the small bowel are numerous and meet within the duodenum and the bed of the pancreas.
  • Collateral vessels within the colon meet at the splenic flexure and descending/sigmoid colon.
  • The splanchnic circulation can receive up to 30% of the cardiac output.
  • Watershed Areas:
  • These areas, which are inherently at risk for decreased blood flow, are known as Griffiths' point and Sudeck's point.
  • These are the most common locations for colonic ischemia.
  • Protective Responses:
  • Abundant collateralization.
  • Autoregulation of blood flow.
  • Ability to increase oxygen extraction from the blood.
  • Occlusive Ischemia:
  • Result of disruption of blood flow by an embolus or progressive thrombosis in a major artery supplying the intestine.
  • In >75% of cases, emboli originate from the heart and preferentially lodge in the SMA just distal to the origin of the middle colic artery.
  • Progressive stenosis of typically two of the three major vessels supplying the intestine is required for the development of chronic intestinal angina.
  • Involvement of the SMA is most worrisome.
  • Nonocclusive Ischemia:
  • Disproportionate mesenteric vasoconstriction (arteriolar vasospasm) in response to a severe physiologic stress such as shock.
  • If left untreated, early mucosal stress ulceration will progress to full-thickness injury.

3.1 Anatomical Vulnerability

  • Griffiths' point:
  • Located at the splenic flexure.
  • Common location for colonic ischemia.
  • Sudeck's point:
  • Located at the descending/sigmoid colon.
  • Common location for colonic ischemia.

4. CLINICAL FEATURES

  • Chronic Mesenteric Ischemia (CMI):
  • Patients typically present with insidious onset of symptoms.
  • Classically present with recurrent episodes of acute dull, crampy, postprandial epigastric pain, which has also been referred to as 'intestinal angina'.
  • Patients also describe fear of eating resulting in weight loss.
  • Duration of symptoms is typically 6–12 months.
  • Physical examination will often reveal a malnourished patient with other manifestations of atherosclerosis.
  • Acute Mesenteric Ischemia (AMI):
  • Nonspecific presentation and requires a high index of suspicion for the diagnosis.
  • The most common complaint, occurring in 95% of cases, is severe, acute, nonremitting abdominal pain that is strikingly out of proportion to the physical findings.
  • Associated symptoms:
  • Nausea (44%).
  • Vomiting (35%).
  • Diarrhea (35%).
  • Blood per rectum (16%).
  • Later findings will demonstrate peritonitis and cardiovascular collapse.
  • Patients with embolic ischemia are typically older adults with underlying conditions that predispose to embolism such as atrial fibrillation, prior embolic event, or recent infective endocarditis.
  • Thrombotic ischemia typically presents as an acute occlusion in patients with underlying atherosclerotic disease who may have been previously diagnosed with CMI.
  • AMI is a surgical emergency requiring emergent admission to a monitored bed or intensive care unit for resuscitation with fluids and broad-spectrum antibiotics in addition to further evaluation.
  • Specific clinical features can help differentiate the underlying etiology, whether embolic or thrombotic.

4.1 Physical Examination Findings

  • Malnourished patient.
  • Other manifestations of atherosclerosis.
  • Peritonitis (later findings).
  • Cardiovascular collapse (later findings).

5. DIFFERENTIAL DIAGNOSIS

  • Gastrointestinal malignancies should be ruled out.
  • Other possible causes should be ruled out via esophagogastroduodenoscopy, colonoscopy, abdominal computed tomography (CT) scan, and abdominal ultrasound examination.

6. INVESTIGATIONS & DIAGNOSIS

  • Duplex Ultrasound:
  • Gained popularity as a screening tool for evaluation of the mesenteric vessels due to high sensitivity and specificity.
  • Mesenteric duplex scan demonstrating a high peak velocity of flow in the SMA is associated with an ~80% positive predictive value of mesenteric ischemia.
  • More significantly, a negative duplex scan virtually precludes the diagnosis of mesenteric ischemia.
  • Important to perform the test while the patient is fasting because the presence of increased bowel gas prevents adequate visualization of flow disturbances within the vessels or the lack of a vasodilation response to feeding during the test.
  • Computed Tomography Angiography (CTA):
  • Thin-sliced CT angiography is the gold standard diagnostic tool in assessing the degree of atherosclerotic disease of the aortic and visceral vessels as well as evaluating the bowels.
  • Venous phase can also help diagnose mesenteric vein thrombosis.
  • CTA with 1-mm or thinner cuts should be used to detect mesenteric arterial occlusive disease most likely from embolic or thrombotic etiology and is the gold standard.
  • Additional Modalities:
  • Electrocardiogram (ECG).
  • Echocardiogram.
  • Esophagogastroduodenoscopy.
  • Colonoscopy.

6.1 Diagnostic Algorithm

  • Step 1: Clinical Suspicion
  • High index of suspicion from the history and physical exam despite normal laboratory findings.
  • If CT angiography verifies acute embolic occlusion of the SMA, surgical exploration should not be delayed.
  • Step 2: Imaging
  • Duplex ultrasound (Screening).
  • CTA (Gold Standard).
  • CT venous phase (for venous thrombosis).
  • Step 3: Intervention
  • If diagnosis of intestinal ischemia is being considered, consultation with a surgical service is necessary.
  • Often the decision to operate is made on a high index of suspicion from the history and physical exam despite normal laboratory findings.

7. MANAGEMENT & TREATMENT

  • Chronic Mesenteric Ischemia (CMI):
  • Management includes aggressive medical therapy of atherosclerotic disease including cessation of smoking and antiplatelet and lipid-lowering medications.
  • A full cardiac and vascular evaluation should be performed before intervention on CMI.
  • Treatment, involving either endovascular, open surgical, or hybrid revascularization, should be individualized based on the patient's comorbidities and anatomy.
  • Endovascular revascularization involves targeted vessel treatment with visceral stents with the SMA anatomy being the key determinant.
  • The revascularization of the celiac axis and IMA represents secondary focal points, offering potential therapeutic benefits.
  • This approach becomes particularly relevant when the SMA is deemed unsuitable for intervention or when technical outcomes are deemed suboptimal.
  • Angioplasty with endovascular stenting in the treatment of CMI is associated with an 80% long-term success rate.
  • Open revascularization should be considered in patients with lesions not amenable to endovascular treatment, such as severe calcification, longer lesions, small vessel diameter, or failed endovascular interventions, or in a specific subset of younger, healthier patients, in whom the potential long-term advantages may outweigh the heightened perioperative risks.
  • Open revascularization involves antegrade bypass from the supraceliac aorta or retrograde bypass typically from the common or external iliac arteries with a synthetic or autogenous graft to the targeted vessels, usually the SMA and/or celiac artery.
  • Retrograde open mesenteric stenting (ROMS) is a hybrid approach, combining aspects of both traditional open surgical bypass and percutaneous endovascular therapy.
  • ROMS is primarily indicated for treating mesenteric ischemia, both acute and chronic, particularly in cases where conventional endovascular or open surgical approaches are not feasible or have been unsuccessful.
  • This includes scenarios where there is significant stenosis or occlusion in the mesenteric arteries that cannot be adequately addressed through less invasive percutaneous methods from the aorta or in situations where immediate direct visualization and potential resection of the bowel are necessary or due to the presence of necrosis or perforation.
  • The technique involves a laparotomy that allows for direct bowel assessment and the exposure and stenting of the SMA using a retrograde approach through the midsegment of the SMA, thus allowing for immediate revascularization, assessment of bowel viability, and, if necessary, bowel resection.
  • ROMS also offers the advantage of faster operative times compared to traditional bypass and avoids the placement of prosthetic material in potentially contaminated peritoneal cavities, which is a significant concern in the setting of bowel necrosis and peritonitis.
  • Acute Mesenteric Ischemia (AMI):
  • Patients with suspected AMI should be given a heparin bolus immediately and started on a therapeutic heparin drip.
  • Correction of electrolyte abnormalities and empiric broad-spectrum antibiotic therapy should also be initiated instantly.
  • The goal of operative exploration is to resect compromised bowel, restore blood supply, and preserve all viable bowel.
  • The entire length of the small and large bowel beginning at the ligament of Treitz should be evaluated.
  • The SMA artery should be localized, typically at the mesocolon of the transverse colon.
  • A transverse arteriotomy of the SMA should be made with removal of embolus with an embolectomy Fogarty catheter passed in a retrograde and antegrade manner to restore blood flow.
  • In the case of SMA occlusion where the embolus usually lies just proximal to the origin of the middle colic artery, the proximal jejunum is often spared while the remainder of the small bowel up to the transverse colon may become ischemic.
  • Nonviable bowel should be resected.
  • Questionable bowel is disproportionate to the clinical findings that ischemia initiates from the mucosal layer and progresses toward the serosal layer.
  • This may be associated with nausea (44%), vomiting (35%), diarrhea (35%), and blood per rectum (16%).
  • Later findings will demonstrate peritonitis and cardiovascular collapse.
  • Specific clinical features can help differentiate the underlying etiology, whether embolic or thrombotic.
  • Patients with embolic ischemia are typically older adults with underlying conditions that predispose to embolism such as atrial fibrillation, prior embolic event, or recent infective endocarditis.
  • Thrombotic ischemia typically presents as an acute occlusion in patients with underlying atherosclerotic disease who may have been previously diagnosed with CMI.
  • Mesenteric Venous Thrombosis:
  • Treatment includes anticoagulation, resuscitation, and hypercoagulable workup.
  • Broad-spectrum antibiotics and support cardiac output are indicated.
  • Avoid vasoconstrictors.

Table 1 — Table 340-1 Overview of the Management of Acute Intestinal Ischemia

CONDITION KEY TO EARLY DIAGNOSIS TREATMENT OF UNDERLYING CAUSE TREATMENT OF SPECIFIC LESION TREATMENT OF SYSTEMIC CONSEQUENCE
Arterio-occlusive mesenteric ischemia 1. Arterial embolus Computed tomography angiography (CTA) Early laparotomy Anticoagulation Cardioversion Thrombectomy Broad-spectrum antibiotics
2. Arterial thrombosis Duplex ultrasound CTA Anticoagulation Broad-spectrum antibiotics Resuscitation Endovascular approach: thrombolysis, angioplasty, and stenting Endarterectomy/thrombectomy or vascular bypass Assess viability and resect nonviable bowel Anticoagulation Resuscitation Broad-spectrum antibiotics Emergent surgical intervention Assessment of bowel
Mesenteric venous thrombosis CTA with venous phase Anticoagulation Resuscitation Anticoagulation Anticoagulation Hypercoagulable workup Resuscitation Venous thrombosis Broad-spectrum antibiotics Support cardiac output Avoid vasoconstrictors
Nonocclusive mesenteric ischemia CT Vasospasm: Hypoperfusion: Vasospasm: Intraarterial vasodilators Hypoperfusion: Support cardiac output Vasospasm: Resuscitation Broad-spectrum antibiotics Avoid vasoconstrictors Hypoperfusion: Support cardiac output Assess viability and resect dead bowel Avoid vasoconstrictors

7.1 Surgical Interventions

  • Embolectomy:
  • Removal of embolus with an embolectomy Fogarty catheter passed in a retrograde and antegrade manner.
  • Restores blood flow.
  • Vascular Bypass:
  • Antegrade bypass from the supraceliac aorta.
  • Retrograde bypass typically from the common or external iliac arteries.
  • Uses synthetic or autogenous graft to the targeted vessels, usually the SMA and/or celiac artery.
  • Bowel Resection:
  • Nonviable bowel should be resected.
  • The entire length of the small and large bowel beginning at the ligament of Treitz should be evaluated.

8. PROGNOSIS & COMPLICATIONS

  • Mortality rate of AMI is >50%.
  • The most significant indicator of survival is the timeliness of diagnosis and treatment.
  • Complications:
  • Peritonitis.
  • Cardiovascular collapse.
  • Bowel necrosis.
  • Perforation.

9. SPECIAL CONSIDERATIONS

  • Age Groups:
  • Older adults with underlying conditions that predispose to embolism such as atrial fibrillation, prior embolic event, or recent infective endocarditis.
  • Younger, healthier patients, in whom the potential long-term advantages may outweigh the heightened perioperative risks.
  • Patients above the age of 50, especially those with coexisting conditions like myocardial infarction, congestive heart failure, aortic insufficiency, and renal or liver disease, who are also undergoing cardiovascular surgery, face the highest risk.

10. KEY PEARLS & CLINICAL TRAPS

  • Pain out of proportion to physical exam is the hallmark clinical feature of acute mesenteric ischemia.
  • Griffiths' and Sudeck's points are watershed areas within the colonic blood supply and common locations for ischemia.
  • Mortality with acute presentation remains high (between 50 and 80%).
  • A negative duplex scan virtually precludes the diagnosis of mesenteric ischemia.
  • Timeliness of diagnosis and treatment is the most significant indicator of survival in acute intestinal ischemia.
  • ROMS is a hybrid approach indicated when conventional endovascular or open surgical approaches are not feasible.

Figures & Illustrations

Reproduced from Harrison's 22nd Edition.

Figure 1

Mesenteric 340 is FIGURE 340-1 Blood supply to the intestines...

Caption: Mesenteric 340 is FIGURE 340-1 Blood supply to the intestines includes the celiac artery, superior mesenteric artery (SMA), inferior mesenteric artery (IMA), and branches of the internal iliac artery (IIA). Griffiths’ and Sudeck’s points, indicated by shaded areas, are watershed areas within the colonic blood supply and common locations for ischemia. Chronic diarrhea may also be noted. Duration of symptoms is typically 6–12 months. Physical examination will often reveal a malnourished — Figure 340-1: Blood supply to the intestines includes the celiac artery, superior mesenteric artery (SMA), inferior mesenteric artery (IMA), and branches of the internal iliac artery (IIA). Griffiths' and Sudeck's points, indicated by shaded areas, are watershed areas within the colonic blood supply and common locations for ischemia.

Generated from Harrison's Principles of Internal Medicine, 22nd Edition.