Introduction

Ischaemic bowel disease can be divided into acute mesenteric ischaemia, chronic mesenteric ischaemia, and colonic ischaemia. This article will predominantly focus on acute mesenteric ischaemia.

Acute mesenteric ischaemia is a surgical emergency. It is characterised by a sudden lack of blood supply or perfusion to the intestines, leading to acute ischaemia and subsequently necrosis, eventually resulting in perforation. There are several important causes, including arterial embolism, arterial thrombosis, venous thrombosis, and non-occlusive causes. Urgent recognition and management is required to prevent bowel necrosis and extensive resection.

Anatomy (1,2)

Visceral blood supply to the foregut, midgut and hindgut. Schematic of thrombus occluding SMA main trunk (3).

Blood supply to the bowel:

Foregut 

• Includes the oesophagus, stomach, pancreas, liver, gallbladder and duodenum (proximal to the major duodenal papilla/sphincter of Oddi and entrance point of the common bile and splenic ducts).
• Supplied by the Coeliac trunk (T12 level from aorta). The proximal duodenum is supplied by the Superior Pancreaticoduodenal arteries, which come off the Gastroduodenal artery branch of the Coeliac trunk.

Midgut 

• Includes duodenum distal to the major duodenal papilla, jejunum, ileum, caecum and ascending colon, and proximal 2/3 of the transverse colon.
• Supplied by the Superior mesenteric artery (SMA, L1 level from aorta). This gives off several branches within the mesentery, forming anastomotic loops (arterial arcades) which then give off straight arteries to the small bowel (vasa recta).
• Jejunum – fewer arcades, longer vasa recta
• Ileum – more arcades, shorter vasa recta

Arterial supply to the jejunum and ileum highlighting the arterial arcades and vasa recta.

Source: Henry Gray (1918) Anatomy of the Human Body, Wikimedia Commons. Public domain image.

• NB the SMA also gives off the Inferior Pancreaticoduodenal arteries proximally, which anastomose with the Superior Pancreaticoduodenal arteries arising from the Coeliac trunk.

Hindgut

• Includes distal 1/3 of the transverse colon, descending colon, sigmoid colon to the upper anal canal (superior to the dentate line).
• Supplied by the Inferior mesenteric artery (IMA, L3 level from aorta).
• The splenic flexure (A.K.A Griffith’s point) of the large bowel is a watershed area as it is located at the junction between the midgut and hindgut. It receives collateral blood supply from both the SMA and IMA via the Marginal artery (of Drummond). Clinically, this is important as an area susceptible to ischaemia, e.g. in ischaemic colitis.

Causes (4,5)

Acute mesenteric arterial embolus (40-50%)

• Caused by an embolus, usually occluding SMA
• Associated with AF
• Can be iatrogenic from interventional radiology (IR) procedures rupturing atherosclerotic plaques
• Generalised, constant abdominal pain out of proportion to clinical findings – sudden onset
• Profuse diarrhoea (+/- blood)

Acute mesenteric arterial thrombosis (15-20%)

• Presents similarly to AMAE
• Can have longer preceding history of mesenteric angina/chronic mesenteric ischaemia due to atherosclerotic narrowing
• Results from acute-on-chronic event with thrombosis of atherosclerotic plaque
• Associated with atherosclerosis
• Risk factors: hypertension, smoking, hyperlipidaemia, diabetes

Non-occlusive mesenteric ischaemia (20%)

• Associated with low flow states and comorbidities which compromise perfusion e.g. HF, MI or arrhythmia, anaemia, shock, sepsis, hypovolaemia (e.g. due to dialysis)
• Infarction from mucosa outwards

Acute mesenteric venous thrombosis (5-15%)

• Longer history occurring over weeks
• Frequently affects superior mesenteric vein
• RFs include any hypercoagulable states, particularly thrombophilia and COCP use. Also associated with liver cirrhosis and portal hypertension, pancreatitis, malignancy, autoimmune disease, although can be idiopathic

Other

Mesenteric angina

• A form of chronic mesenteric ischaemia
• Gradually reduced blood supply over time due to atherosclerosis, can lead to acute thrombosis
• Symptoms of postprandial abdominal discomfort/pain +/- weight loss due to avoidance or fear of eating (sitophobia)
• Can be asymptomatic due to collateralisation of blood vessels
• More common in elderly and female patients
• RFs same as for acute thrombosis

Ischaemic colitis

• Ischaemia of the colon
• Mix of non-occlusive and atherosclerosis type ischaemia
• Reduced blood supply results in inflammation but not necessarily infarction or necrosis (requiring resection)
• Splenic flexure of colon (Griffith’s point) particularly vulnerable to ischaemia at watershed point
• Typically managed conservatively (IVF, antibiotics) with gastroenterology input, unless indications for acute surgical intervention (infarction, perforation, peritonitis, massive haemorrhage, fulminant colitis)
• Can be investigated with endoscopy

Rare

Vasculitis – e.g. rheumatoid arthritis, polyarteritis nodosa, systemic lupus erythematosus, dermatomyositis, Takayasu arteritis, and thrombo-angiitis obliterans

External compression – e.g. tumours, median arcuate ligament syndrome (MALS) compressing coeliac trunk

Aortic dissection

Main causes of acute mesenteric ischaemia. Slide from MTB Final Year Series: General surgery – Acute conditions presentation

Clinical features

• Sudden onset severe generalised, constant abdominal pain, out of proportion with clinical findings (longer history in venous)
• Nausea + vomiting
• Diarrhoea, may be bloody
• Generalised, non-specific abdominal tenderness, if bowel is necrotic or has perforated may have signs of peritonism or peritonitis
• Clinical features suggesting underlying cause, e.g. AF or arrhythmia, recent MI, stigmata of cardiovascular disease or smoking, signs of anaemia, hypovolaemia or sepsis
• Note that there is a large differential diagnosis for acute abdominal pain

Investigations

Bedside

• VBG/ABG – importantly gives you lactate and pH – these are important markers of organ perfusion and ischaemia. Often shows metabolic acidosis.
• Urine dip, pregnancy test, CSU
• ECG – may show causative arrhythmias e.g. AF, or acute MI which can also precipitate ischaemia through embolization of a mural thrombus
• Stool sample for MC&S if diarrhoea or loose stools

Bloods

• FBC, U&E, LFT, CRP, G&S x2
• Amylase – to r/o pancreatitis, although may also be raised in other causes of abdominal pain, such as mesenteric ischaemia, DKA, ectopic pregnancy and bowel perforation
• Clotting – patients may have thrombophilia or anticoagulated due to AF, and may need urgent surgery
• Cultures

Imaging (6)

• Key imaging investigation is CT angiogram with IV contrast – demonstrates blood flow through mesenteric arteries and occlusions, as well as ischaemic changes such as infarction, and signs of perforation:
  • • Bowel wall thickness and enhancement
    • Bowel oedema
    • Pneumatosis intestinalis
    • Pneumatosis portalis
    • Pneumoperitoneum 
    • Free fluid
    • Any collateral vessels (suggesting chronicity)

• Erect CXR – can show subdiaphragmatic air indicating pneumoperitoneum from perforation

Normal radiographic SMA anatomy for comparison.

Case courtesy of Mohamed Saber, <a href=”https://radiopaedia.org/?lang=gb”>Radiopaedia.org</a>. From the case <a href=”https://radiopaedia.org/cases/84641?lang=gb”>rID: 84641</a> (7)

Annotated CTA showing complete occlusion of distal SMA main trunk sparing left proximal jejunal branches and right middle colic artery. Distal jejunal branches, ileal branches, ileocolic and right colic arteries were occluded.

Case courtesy of Mohamed Saber, <a href=”https://radiopaedia.org/?lang=gb”>Radiopaedia.org</a>. From the case <a href=”https://radiopaedia.org/cases/84641?lang=gb”>rID: 84641</a> (7)

Management (4,5)

Early resuscitation

• Keep NBM, start IVF, insert catheter + keep strict fluid balance
• Analgesia
• Broad spectrum antibiotics – due to risk of perforation and bacterial translocation from the gut
• Early ITU input – these are very unwell patients
• Early surgical/vascular input
• Monitoring pH and lactate

NOMI 

• Urgent correction of underlying medical cause of hypoperfusion
• Endovascular options – angiography and local delivery of vasodilators

Venous ischaemia

• Anticoagulation first line (initially IV heparin, then converted to oral warfarin)

Definitive surgical

• Depends on the clinical picture, timing, anatomical location, severity, imaging, patient factors and surgical fitness

• Urgent surgery is indicated where there is evidence on imaging of infarction or perforation, and if the clinical picture is suggestive of peritonitis (in any cause)

Revascularisation

• IR vs surgical management – IR (endovascular) is increasingly preferable as it is less invasive and carries fewer risks
• Suitable only if no urgent indications for surgery (as above)
• IR – embolectomy, thrombectomy or thrombolysis, angioplasty + stent if suggestive of more chronic picture with critical atherosclerotic narrowing
• Open surgical – thrombectomy/embolectomy, arterial bypass e.g. aortomesenteric/iliomesenteric, mesenteric endarterectomy
• Systemic anticoagulation with IV heparin infusion + APTT monitoring

A 20cm segment of ischaemic proximal ileum found at surgery. Resection and anastomosis were performed.

Due to thrombus in the superior mesenteric vein. 

Case courtesy of Ian Bickle, <a href=”https://radiopaedia.org/?lang=gb”>Radiopaedia.org</a>. From the case <a href=”https://radiopaedia.org/cases/52750?lang=gb”>rID: 52750</a> (8)

Resection of necrotic/non-salvageable bowel

• May be taken back to theatre for re-look laparotomy to re-assess viability of remaining bowel
• Many undergo stoma formation
• At risk of short gut syndrome*

* Substantial portions of the small intestine are absent. Typically, less than 200 cm of residual short bowel is present. This results in a loss of surface area for fluid, nutrient, and medication absorption, causing an inability to maintain protein-energy, fluid, electrolyte, or micro-nutrient balance when ingesting a conventionally accepted, normal diet. May require TPN. (9)

References
 
1. The Small Intestine – Duodenum – Jejunum – Ileum – TeachMeAnatomy [Internet]. [cited 2025 Jan 7]. Available from: https://teachmeanatomy.info/abdomen/gi-tract/small-intestine/#section-677b9c459dc35

2. The Colon – Ascending – Transverse – Descending – Sigmoid – TeachMeAnatomy [Internet]. [cited 2025 Jan 7]. Available from: https://teachmeanatomy.info/abdomen/gi-tract/colon/#section-67764e78eb9ce

3. Theodore S, Xia T, Saillant N. Intestinal Ischemia — Etiology and Foundational Concepts. NEJM Evidence. 2024 Feb 27;3(3):EVIDra2300266. 

4. Acute Mesenteric Ischaemia – Causes – Management – TeachMeSurgery [Internet]. [cited 2025 Jan 7]. Available from: https://teachmesurgery.com/vascular/peripheral/mesenteric-ischaemia/

5. Ischaemic bowel disease – Symptoms, diagnosis and treatment | BMJ Best Practice [Internet]. [cited 2025 Jan 7]. Available from: https://bestpractice.bmj.com/topics/en-gb/3000223

6. Gaillard F. Radiopaedia. [cited 2025 Jan 7]. Mesenteric ischaemia | Radiology Reference Article | Radiopaedia.org. Available from: https://radiopaedia.org/articles/mesenteric-ischaemia?lang=gb

7. Saber M. Radiopaedia. [cited 2025 Jan 7]. Arterial occlusive mesenteric ischaemia | Radiology Case | Radiopaedia.org. Available from: https://radiopaedia.org/cases/arterial-occlusive-mesenteric-ischaemia

8. Bickle I. Radiopaedia. [cited 2025 Jan 7]. Ischaemic small bowel | Radiology Case | Radiopaedia.org. Available from: https://radiopaedia.org/cases/ischaemic-small-bowel-1

9. Pironi L, Arends J, Baxter J, Bozzetti F, Peláez RB, Cuerda C, et al. ESPEN endorsed recommendations. Definition and classification of intestinal failure in adults. Clinical Nutrition. 2015 Apr;34(2):171–80.

Author and Editor – Dr Daniel Arbide FY2

Last updated 10/11/2025