Question 1

College answer

This question was answered well, as most candidates provided outlines around the specified categories. Pathophysiology involved an outline of various ways in which the blood supply can be disrupted, and diagnosis was based around aspects of history, examination and investigation. Management involved various aspects of resuscitative measures and disease specific measures.

Discussion

This question is functionally identical to Question 12 from the first paper of 2017, except this time the examiners appended "in the critically ill patient", presumably because last time all the trainees spent too much time discussing mesenteric ischaemia among the well patients out in the community. 

Pathophysiology

• Acute mesenteric ischaemia
  • Arterial embolism (40% of cases)
  • Arterial thrombosis from ruptured atheroma (20-35% of cases)
  • Arterial dissection (<5% of cases)
  • Non-occlusive mesenteric hypoperfusion (10-15% of cases)
  • Venous infarction (5-15% of cases)
• Chronic mesenteric ischaemia
  • Gradual onset of arterial insufficiency due to atherosclerosis

History

• History of atherosclerosis
• Hypercoagulable background
• AF
• Vasculitis
• Recent abdominal surgery
• Historical features associated with chronic mesenteric ischaemia, eg:
  • Postprandial pain ("mesenteric angina"), 30-60 minutes after eating
  • Weight loss
  • Diarrhoea or constipation
  • Early satiety

Examination

• Classic “pain out of proportion to examination”
• Epigastric bruit
• Peritonism
• Clinical features of shock

Biochemistry

• Features of organ system dysfunction, eg. rising creatinine
• Raised lactate
• Neutrophilia

Imaging

• Doppler ultrasound of the mesenteric vessels:
  • Arterial flow in mesenteric vessels
  • Portal venous flow 
• CT with IV contrast, two-phase, looking for:
  • Arterial or venous thrombosis
  • Pneumatosis coli
  • Gas in the portal and mesenteric circulation
• Catheter angiography (also allows thrombolysis)
• Diagnostic laparotomy (the college felt this was an essential part of the answer)

Specific management

• Aggressive:
  • Endovascular repair
  • Open repair with or without vascular bypass
  • Catheter-directed clot aspiration or  thrombolysis
  • Stenting of dissected segments
• Conservative:
  • Heparin infusion (this is probably the only therapy required for venous mesenteric ischaemia)

Supportive management

• Airway protection may be required (high risk of aspiration)
• Mechanical ventilation (increased work of breathing due to acidosis)
• Circulatory support (vasodilated shock state)
• Analgesia and anaesthesia (opiates may actually be preferred, as they "rest the gut" by paralysing its motility)
• Neuromuscular junction blockers may help organ perfusion by their effect on abdominal compartment pressure
• Electrolyte correction (particularly correction of acid-base balance)
• Fluid resuscitation (extensive third-space losses are to be expected)
• Abdominal compartment pressure - serial measurements 
• Parenteral nutrition (the patient should remain fasted)
• Antibiotics of a broad spectrum, eg. piperacillin/tazobactam or meropenem