Gastrointestinal and hepatology · Hard
This case is fictional and exists for study. It describes no real patient.
74 years · female
A 74-year-old female presents to the emergency department with a 6-hour history of severe, continuous abdominal pain accompanied by nausea and two episodes of bloody diarrhoea. She has a past medical history of hypertension and atrial fibrillation but self-discontinued her anticoagulation therapy three months ago. On examination, she is in marked distress and writhing in pain. Her abdomen is soft with mild, diffuse tenderness on deep palpation, but there is no localized guarding, rigidity, or rebound tenderness. Digital rectal examination demonstrates dark red blood on the glove. Auscultation reveals hypoactive bowel sounds.
Vital signs
- HR
- 118 bpm
- BP
- 92/58 mmHg
- RR
- 24/min
- Temp
- 37.9 °C
- SpO₂
- 94%
Examination findings
- Severe pain out of proportion to abdominal physical examination findings
- Mild diffuse abdominal tenderness without signs of peritonitis
- Irregularly irregular cardiac rhythm
- Dark red blood present on digital rectal examination
Investigations
| White cell count | 19.2 10^9/L | reference: 4.0-11.0 |
| Serum Lactate | 4.5 mmol/L | reference: 0.5-2.2 |
| Arterial pH | 7.26 | reference: 7.35-7.45 |
| Serum Bicarbonate | 15 mmol/L | reference: 22-28 |
| Base excess | -8 mmol/L | reference: -2.0 to +2.0 |
Question 1 of 3
What is the most likely diagnosis?
The classic presentation of acute mesenteric ischaemia (AMI) is severe, constant abdominal pain out of proportion to physical examination findings in a patient with a cardiovascular risk factor (such as non-anticoagulated atrial fibrillation leading to superior mesenteric artery embolism). Marked leucocytosis, high lactate, and metabolic acidosis reflect bowel necrosis. Ischaemic colitis typically affects watershed areas (e.g., splenic flexure) presenting with localized left lower quadrant pain and haematochezia, usually with a milder systemic response. Perforated peptic ulcer presents with localized or generalized overt peritonitis (rigid abdomen). Acute diverticulitis presents with localized tenderness (usually left lower quadrant) and peritonism.
Teaching point: Acute mesenteric ischaemia should be strongly suspected in patients with atrial fibrillation presenting with severe abdominal pain out of proportion to physical exam findings and elevated serum lactate.
Question 2 of 3
Which investigation is the single most appropriate to confirm the diagnosis?
CT mesenteric angiography (CTA) is the non-invasive gold standard investigation for acute mesenteric ischaemia, offering high sensitivity and specificity for demonstrating arterial occlusion and assessing bowel wall viability. Plain radiographs (chest/abdominal) may rule out perforation or ileus but are non-specific and insensitive for early bowel ischaemia. Endoscopy (sigmoidoscopy) is useful for ischaemic colitis but is contraindicated or non-diagnostic in acute small bowel mesenteric ischaemia and risks bowel perforation. Abdominal ultrasound is limited by retroperitoneal gas and bowel gas artifact in acute abdominal presentations.
Teaching point: CT mesenteric angiography is the diagnostic modality of choice to confirm acute mesenteric ischaemia.
Question 3 of 3
Alongside fluid resuscitation and analgesia, what is the single most appropriate next step in management?
Acute mesenteric ischaemia is a life-threatening surgical emergency. Definitive treatment requires urgent senior surgical involvement for emergency revascularisation (endovascular or open) and resection of non-viable bowel. Systemic thrombolysis with alteplase is contraindicated in acute abdomen with potential bowel necrosis due to high risk of life-threatening severe intra-abdominal haemorrhage. Decompression colonoscopy is used for pseudo-obstruction, not mesenteric ischaemia. Oral anticoagants have no role in the acute emergency management phase.
Teaching point: Immediate surgical evaluation for operative revascularisation and bowel resection is critical in managing acute mesenteric ischaemia.
Key learning points
- Disproportionate abdominal pain relative to physical signs in an un-anticoagulated atrial fibrillation patient strongly suggests acute mesenteric ischaemia.
- Elevated serum lactate and metabolic acidosis indicate ongoing tissue hypoperfusion and bowel ischaemia.
- CT mesenteric angiography is the diagnostic investigation of choice, and emergency surgical consultation must not be delayed.
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