Intestinal ischemia occurs if bowel perfusion cannot meet the metabolic demands of the intestine. This relative hypoperfusion may be the result of atherosclerosis, thromboembolic disease, or severe systemic hypotension. Intestinal ischemia is often classified based on its onset and location: acute mesenteric ischemia (AMI), chronic mesenteric ischemia (CMI), or colon ischemia (ischemic colitis). Each type has a different manifestation and treatment. AMI is a vascular emergency and manifests with sudden, severe abdominal pain; CMI manifests with chronic recurrent postprandial abdominal pain. Colon ischemia manifests with cramping abdominal pain and bloody diarrhea and is often self-limited, though, rarely, it may progress to fulminant bowel necrosis. Diagnosis is primarily made with cross-sectional imaging and CT angiography (CTA). Laboratory studies are used to determine disease severity and monitor the effects of resuscitation. Early diagnosis, surgical consultation, and definitive treatment with urgent surgical or endovascular revascularization are essential in AMI, which has a mortality rate of > 50%. Patients with CMI have a more favorable prognosis but still benefit from timely revascularization. Colon ischemia is primarily managed with supportive care and monitoring for symptom progression. Bowel perforation, intestinal infarct, and/or sepsis are associated with a poor prognosis, regardless of the type of intestinal ischemia.
|Overview of intestinal ischemia|
|Acute mesenteric ischemia||Chronic mesenteric ischemia|
|Sites of ischemia|
- Acute or chronic hypoperfusion of the colon; typically transient and self-limited (nongangrenous form), but can also result in severe acute ischemia with bowel infarction (gangrenous form)
- Often used interchangeably with the term ischemic colitis.
- Most common type of intestinal ischemia
- Most commonly affects individuals > 60 years of age
- ∼ 80% of cases are nongangrenous, resolving without surgery
- Isolated right-sided colon ischemia (IRCI): 10–25% of cases 
- Hypotension, hypovolemia: e.g., due to sepsis, dehydration, hemorrhage
- Chronic disease: e.g., diabetes mellitus, cardiovascular disease, renal insufficiency
- Thrombophilia: e.g., in antiphospholipid syndrome
- Surgery: e.g., aortic aneurysm repair; , abdominal surgery affecting mesenteric arteries, cardiac surgery 
- Medications and recreational drug use: e.g., vasoconstrictive drugs, immunomodulators, cocaine
- Constipation, irritable bowel syndrome, colonic obstruction
Older patients with colon ischemia.  are at especially high risk for developing
- Intestinal blood flow of the superior mesenteric artery (SMA) and/or inferior mesenteric artery (IMA) is acutely compromised → intestinal hypoxia → intestinal wall damage → mucosal inflammation and possibly bleeding → possible progression to infarction and necrosis (gangrenous colon ischemia) → disruption of the mucosal barrier and perforation → release of bacteria, toxins, and vasoactive substances → life-threatening sepsis
- Tissue damage depends on the severity and duration of perfusion disruption.
- Tissue damage may be exacerbated by . 
- Sites of compromise
Clinical features 
- Classic presentation of colon ischemia
- Signs of gangrenous colon ischemia
- Signs of systemic complications
Red flags in colon ischemia
The following are poor prognostic markers:
- Clinical presentation
The severity of colon ischemia determines the appropriate approach to diagnostics and treatment. . 
- Mild colon ischemia: , no IRCI, and no
- Moderate colon ischemia: 1–3
- Severe colon ischemia
All patients with suspected colon ischemia
- Obtain laboratory studies and stool studies.
- Perform CT abdomen with IV and oral contrast.
- Determine disease severity.
- , including IRCI
CT abdomen is the preferred initial test for all patients with suspected colon ischemia.
- There are no specific diagnostic laboratory studies for colon ischemia.
- Blood tests help assess the severity of colon ischemia; findings in severe colon ischemia include:
- Stool studies are indicated to rule out differential diagnoses (e.g., ).
- CT abdomen with IV and PO contrast
Other imaging studies
- CTA or MR angiography: indicated if there is suspicion of IRCI or AMI and in severe colon ischemia 
- Splanchnic angiography: Consider if CT findings are negative but the patient has symptoms consistent with impending AMI. 
Plain abdominal radiograph
- May be performed during urgent assessment of acute abdomen
- Potential findings are nonspecific (e.g., air-filled, distended bowel).
- Indication: suspected mild colon ischemia or moderate colon ischemia
- Contraindications: or gangrenous bowel (e.g., pneumatosis on imaging)
Differential diagnoses 
- Colon ischemia usually resolves spontaneously and requires no specific therapy.
- Surgical intervention is required in severe cases (e.g., patients with gangrenous bowel).
- Initiate supportive care (e.g., analgesia, fluid therapy, and bowel rest) for all patients.
- Urgently consult surgery for patients with severe colon ischemia, signs of peritonitis, and/or hemodynamic instability.
- Consider antibiotic treatment for patients with moderate or severe colon ischemia.
- Admit patients with severe colon ischemia to intensive care.
- Consider outpatient management if symptoms are very mild.
- Supportive care
- Consider in moderate colon ischemia and severe colon ischemia.
- Give broad-spectrum antibiotics that cover both aerobic and anaerobic bacteria.
- For potential regimens, see “Empiric antibiotic therapy for intraabdominal infections.”
Management of the underlying condition, e.g.:
- Urgent indications
- Other indications
- Acute: bowel perforation, peritonitis, sepsis, multiple organ failure
- Chronic: chronic ischemic colitis, colon strictures
- Overall mortality: 4–12%
- Recurrence rate: up to 10% within 5 years
- Acute reduction in arterial or venous blood flow to the small intestine; may result in bowel ischemia or infarct 
- Most commonly occurs in individuals > 60 years of age 
- Prevalence in patients with acute abdomen: ∼ 1% 
- Mortality: 50–70% 
- Acute mesenteric artery embolism
- Acute mesenteric artery thrombosis
- Nonocclusive mesenteric ischemia
- Mesenteric venous thrombosis
- Sudden interruption of blood flow to small bowel; → intestinal hypoxia → hemorrhagic infarction and necrosis → disruption of the mucosal barrier and perforation → release of bacteria, toxins, and vasoactive substances → life-threatening sepsis
- Sites of vessel occlusion
Clinical features 
- Abdominal pain out of proportion to physical examination
- Diarrhea; bloody in later stages
- Nausea and vomiting, abdominal bloating
- Systemic signs of sepsis
- Peritonitis and acute abdomen in late stages
- Symptom onset and intensity may vary with the etiology of AMI. 
- Acute mesenteric arterial embolism
- Acute mesenteric arterial thrombosis: subacute onset, less severe pain; occurs in patients with a history of abdominal angina 
- Nonocclusive mesenteric ischemia: gradual onset of symptoms over several days; patients may be asymptomatic
- Mesenteric venous thrombosis: mild, nonspecific symptoms that worsen gradually
Approach to management
- Perform an ABCDE survey and initiate resuscitation as indicated.
- Consult general surgery urgently for patients with peritonitis or hemodynamic instability.
- Consider .
- Obtain CTA to determine the site and possible etiology of the occlusion.
- Order routine laboratory studies, lactate, and (e.g., type and screen).
- Admit the patient to the ICU or organize direct transfer to the operating room.
- Consult vascular surgery and/or interventional radiology for definitive treatment.
- Start anticoagulation with full-dose heparin.
- Evaluate and treat the underlying disease (e.g., echocardiography for Afib).
- Indication: all patients with suspected AMI 
- Vascular pathology: embolism, thrombosis, stenosis, or dissection of mesenteric vessels
- Bowel wall thickening, hypoperfusion, hemorrhage
- Bowel dilation, air-fluid levels, mesenteric fat stranding
- Pneumatosis intestinalis
- Portal venous gas
Do not delay CTA while waiting for other diagnostic test results. 
- Consider catheter angiography in consultation with a specialist. 
- X-ray abdomen: may be considered only as a quick screening method for bowel perforation or obstruction 
Laboratory studies 
- CBC: leukocytosis, ↑ Hct (due to volume depletion) or ↓ Hct (due to GI bleed)
- ↑ Serum lactate
- CMP: electrolyte abnormalities, ↑ AST
- Blood gas: metabolic acidosis, ↓ HCO3-
- Other: ↑ D-dimer , ↑ amylase, ↑ CPK, ↑ LDH
Initial treatment 
- Initiate supportive measures.
- Insert a nasogastric tube and keep the patient NPO.
- Start broad-spectrum IV antibiotics: See “.”
- Begin unfractionated heparin .
- IV anticoagulation is indicated in all patients without .
- Coordinate heparin administration with the consulting surgical team.
- Consider early palliative care consultation in patients with extensive disease, particularly older patients.
Definitive treatment 
Definitive treatment is determined by the etiology of the AMI, the integrity of the bowel wall, and institutional resources .
- Endovascular revascularization
Patients who do not improve after endovascular intervention should undergo surgical intervention. 
Long-term management 
- Recommend lifestyle modifications for .
- Optimize treatment of the underlying disease (e.g., , ).
- Lifelong anticoagulation is typically recommended for patients with embolic AMI.
- Lifelong antiplatelet therapy is recommended after any revascularization procedure. 
- Administer supplemental oxygen.
- Obtain IV access with two large-bore peripheral IVs.
- Obtain CTA abdomen and pelvis.
- Admit to the ICU or organize transfer to the operating room.
- Urgently consult surgery and interventional radiology.
- Establish NPO status and insert an NG tube.
- Consider anticoagulation with IV heparin (after discussion with a surgeon).
- Start broad-spectrum IV antibiotics.
- Provide parenteral analgesia.
- Give antiemetics.
- Continue serial laboratory studies and physical examinations.
- Mesenteric artery occlusive disease (MAOD)
- Chronic mesenteric ischemia (CMI):
- Atherosclerosis (see “Risk factors for atherosclerosis”) is the main cause of CMI.
- Less common causes: vasculitis, mesenteric venous thrombosis ,
- Slowly progressing stenosis of two or more of the main mesenteric arteries: SMA, IMA, and/or celiac artery → postprandial mismatch between splanchnic blood flow and intestinal metabolic demand → postprandial pain
- If only one main artery is affected, collateral connections between the arteries can form and compensate for the reduced flow; these patients may be asymptomatic.
- Thrombus formation in addition to stenosis can lead to acute-on-chronic mesenteric ischemia, which leads to AMI.
Clinical features 
- Postprandial abdominal pain: begins 10–30 minutes after eating and lasts 1–2 hours
- Food aversion (: fear of eating because of postprandial pain
- Unintended weight loss
- Nonspecific symptoms: e.g., nausea, diarrhea, bloating
- Abdominal bruit on auscultation
Angiography: to confirm the diagnosis in symptomatic patients
- Findings: Mesenteric artery stenosis of > 70% is typically considered clinically relevant. 
- Laboratory studies: nonspecific; may show findings suggestive of malnutrition 
- Additional testing
Differential diagnoses 
- Malignancy (e.g., gastric cancer, pancreatic cancer)
- Chronic cholecystitis
- Chronic pancreatitis
- Inflammatory bowel disease
- Irritable bowel syndrome
- Infectious gastroenteritis
- Celiac disease
- Peptic ulcer disease
- Offer revascularization to all patients. 
- Medically optimize patients prior to intervention (see “Preoperative management”).
- Provide nutritional therapy while awaiting revascularization.
- Monitor patients with MAOD for symptom development.
- Definitive therapy 
- Endovascular procedures (e.g., stenting) are preferred. ,
- Surgical revascularization is typically reserved for lesions not suitable for an endovascular approach.
- Frequent, small meals and a low-fat diet may provide some symptom relief.
- Total parenteral nutrition should only be considered as a temporary supportive measure.
- Long-term antiplatelet therapy after revascularization 
- Scheduled follow-up examinations for recurrent stenosis