Pain Out of Proportion in a Woman with Atrial Fibrillation

Acute mesenteric ischaemia, almost certainly an embolus to the superior mesenteric artery - she has atrial fibrillation, has been off anticoagulation for three weeks, and presents with the classic triad of severe pain out of proportion to examination, vomiting and a raised lactate in an older patient with AF.

Why the film is not reassuring: plain radiography is normal or non-specific in the majority of early mesenteric ischaemia. It excludes perforation and obstruction; it cannot exclude a dead gut. A normal film plus a lactate of 3.6 in this story should raise, not lower, your concern. Nor does a lactate need to be very high - early on it can be near normal, and a normal value does not exclude the diagnosis.

Immediate actions:

• Resuscitate: IV crystalloid, catheter, oxygen as needed, analgesia (do not withhold it - it will not mask the diagnosis).
• CT angiography of the abdomen and pelvis, immediately. The creatinine of 152 is not a reason to delay - the risk of missing a dead bowel vastly outweighs contrast nephropathy; pre-hydrate as you go.
• Broad-spectrum antibiotics, nothing by mouth, nasogastric tube only if vomiting persists.
• Therapeutic heparin (she is off apixaban and has a presumed thrombus/embolus) unless actively bleeding, and discuss anticoagulation reversal is not needed here.
• Urgent surgical and vascular/IR consultation while the scan is happening - revascularisation within about six hours of symptom onset changes survival.

The CT scanner is the default because it distinguishes embolus from thrombosis, identifies a viable versus dead bowel, and allows planning of endovascular therapy. Go straight to the operating theatre, after rapid resuscitation, if:

• Peritonism develops - guarding, rigidity, rebound, absent bowel sounds - indicating infarction and perforation.
• Pneumoperitoneum or pneumatosis on any imaging.
• Haemodynamic instability that does not respond to fluid resuscitation, or a rapidly rising lactate with worsening acidosis.
• Deterioration during transfer or in the scanner - the patient must be continuously observed by someone senior; a CT suite is a dangerous place for a moribund patient.
• A known allergy or contrast issue where the diagnosis is already clinically overwhelming.

In all cases, the decision to operate is clinical and time-critical; a CT that takes two hours in an unstable patient is worse than a laparotomy. Conversely, a stable patient with a clear embolus and no peritonitis may be best served by endovascular embolectomy/aspiration with surgical back-up on standby.

Diagnostic traps:

• Attributing the pain to gastroenteritis, renal colic, diverticulitis or 'constipation' because the abdomen is soft - the disparity between pain and examination is the whole point of the presentation.
• Reassuring yourself with a normal abdominal X-ray and a normal amylase. Amylase is for pancreatitis; a normal value does nothing to exclude ischaemia.
• Waiting for serial lactates to rise before acting. Lactate is a late and non-specific marker; waiting for it to climb means waiting for infarction.
• Delaying CT angiography because of the creatinine. The diagnosis is life-threatening and time-dependent; contrast is still indicated.
• Assuming anticoagulation rules out the diagnosis: she had stopped apixaban, and even therapeutic anticoagulation does not exclude an embolus.

Management traps:

• Giving laxatives or a prokinetic bowel regimen on a presumed obstruction.
• Withholding analgesia for fear of masking signs - evidence does not support this, and pain relief allows a better examination.
• Failing to involve surgery and vascular/IR early; the window for revascularisation is short and mortality rises steeply with delay.
• Forgetting the atrial fibrillation: she needs anticoagulation and a conversation about why she stopped it, plus rhythm and rate review, before discharge.