Skip to textbook content
Doctor’s PassportTextbook
TopicsAll topics

Loading topic navigation…

Textbook navigation
TopicsAll topics

Loading topic navigation…
Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.

Ischaemic colitis

Gastroenterology and hepatology · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

RapidFull
!
Escalate

Peritonism, haemodynamic instability, severe pain without bleeding, right-sided or pancolonic disease, persistent acidosis, organ failure, pneumatosis, portal venous gas or free perforation raises transmural infarction and death risk. Resuscitate, begin sepsis care where appropriate and involve senior colorectal surgery immediately. Pain out of proportion, atrial fibrillation or small-bowel CT angiographic findings may represent acute mesenteric ischaemia and needs an urgent vascular-surgical pathway.

Synopsis

Recognise colonic hypoperfusion early, distinguish transient mucosal disease from gangrene and acute mesenteric ischaemia, and coordinate supportive, endoscopic and surgical management according to severity.

  • Ischaemic colitis usually presents with sudden cramping abdominal pain followed within hours by rectal blood or bloody diarrhoea after a low-flow or vascular insult.
  • The left colon and watershed zones are frequently affected, but isolated right-colon involvement carries greater severity and should lower the threshold for urgent surgical review.
  • Risk factors include older age, atherosclerosis, heart failure, hypotension, dehydration, recent major surgery, dialysis, thrombophilia and vasoconstricting or constipating medicines.
  • A normal early lactate does not exclude bowel ischaemia; serial physiology, examination and contrast imaging determine urgency.
  • Contrast CT assesses distribution, wall injury, complications and alternative diagnoses; CT angiography is added when acute mesenteric arterial occlusion or severe right-sided disease is suspected.
  • In a stable patient without peritonism, limited lower-GI endoscopy with careful insufflation and biopsies can confirm the pattern and exclude IBD, infection or cancer.
  • Mild transient disease is treated with restoration of perfusion, bowel rest or diet progression and removal of precipitating factors; moderate or severe disease may require antibiotics and closer monitoring.
  • Surgery is indicated for perforation, peritonitis, gangrene, uncontrolled bleeding or clinical deterioration despite non-operative care, not for every CT segment of thickening.

Key red flags

Severe right-sided pattern

Right abdominal pain, little or no bleeding, kidney failure or shock and CT involvement of the ascending colon predicts a worse course and can overlap acute mesenteric ischaemia.

Transmural infarction

Constant worsening pain, involuntary guarding, fever, shock, ileus, acidosis, pneumatosis or portal venous gas suggests necrotic bowel and requires immediate senior surgery rather than diagnostic endoscopy.

Acute mesenteric ischaemia

Pain out of proportion, atrial fibrillation, embolic history, severe diffuse pain or small-bowel hypoenhancement indicates a vascular emergency requiring CT angiography and vascular-surgical involvement.

Investigation priorities

01
Contrast CT abdomen and pelvisFirst step

Map colonic distribution, grade mural injury and detect perforation, obstruction, malignancy or another cause of acute colitis.

Management branches

Initial assessmentGrade bowel and whole-patient risk

Acute pain and rectal blood suggest ischaemic colitis.

  1. Perform ABCDE, establish onset and pain-before-blood sequence, seek shock or vascular triggers and review cardiac, surgical, dialysis and medicine history.
  2. Examine repeatedly for focal versus generalised tenderness, distension and perfusion, sending bloods, lactate and stool tests without using normal results to dismiss the diagnosis.
  3. Obtain contrast CT and discuss CT angiography directly with radiology when right-sided, disproportionate or embolic features suggest acute mesenteric ischaemia.
  4. Involve senior colorectal surgery early for high-risk distribution or physiology, even before peritonism becomes established.

Key medicines

Intravenous crystalloidGive cautious reassessed boluses under the current resuscitation protocol, then replace ongoing deficits according to perfusion, cardiac reserve, renal function and urine output.Heart failure and renal disease increase pulmonary oedema risk. Fluid cannot correct an embolic occlusion or necrotic bowel, so definitive imaging and surgical decisions continue in parallel.
Broad-spectrum antibioticFor moderate, severe or surgically threatened disease, use the locally approved intravenous colonic-sepsis regimen and review daily against cultures, source control and recovery.Evidence and thresholds vary, so mild disease may not require antibiotics. Check allergy, renal function and Clostridioides difficile risk, and never substitute antibiotics for resection of gangrene.
Open full textbook →Answer 2 questions
Sources and review status4 sources · checked 27 Aug 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.

  • ACPGBI emergency colorectal surgery consensusUK specialist assessment, severity and surgical management of emergency colonic ischaemia.
  • BSG acute lower gastrointestinal bleeding guidelineAssessment and investigation when ischaemic colitis presents with acute lower-GI bleeding.
  • NICE NG253 suspected sepsisRecognition and initial treatment when bowel injury produces suspected sepsis or organ dysfunction.
  • RCSEd bowel ischaemia educationRoyal College teaching on presentation and urgent response to bowel ischaemia.

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateRapid draftClinical stateAwaiting reviewJurisdictionUnited Kingdom