A case report: an unsuspected case of acute mesenteric ischaemia

Abstract

Acute mesenteric ischaemia is a severe surgical condition with significant mortality, and it requires prompt recognition and surgical intervention. This report describes a case of a middle-aged gentleman with no previous risk factors who presented with an acute abdomen secondary to mesenteric ischaemia and made a full recovery. This case illustrates that mesenteric ischaemia can occur without the presence of any obvious risk factors and if treated early can result in successful outcomes.

BACKGROUND

This case effectively illustrates the difficulty in diagnosing acute mesenteric ischaemia, a condition with significant clinical importance that, as in this case, can occur without the presence of obvious risk factors. However, what this case also illustrates is that with early identification and treatment the outcomes can be successful.

CASE PRESENTATION

A 54-year-old male presented with a 2 day history of vomiting and colicky lower abdominal pain to the medical ward with a provisional diagnosis of gastroenteritis. The patient was not on any regular medications, had never smoked and had no history of trauma prior to this episode. The abdominal radiograph (AXR) was unremarkable. Blood investigations revealed a white cell count (WCC) of 13.7×10⁹/l and a normal C-reactive protein (CRP). He was managed conservatively, but the following day he developed worsening central abdominal pain and bilious vomiting with mild epigastric tenderness. He had not opened his bowels or passed flatus for 3 days. Digital rectal examination revealed no abnormalities. It was also noted that he developed low-grade pyrexia and the CRP and WCC had risen to 188 and 22.2×10⁹/l, respectively. An ultrasound scan of the abdomen revealed no abnormalities.

He continued to experience nausea and vomiting the next day and his abdomen was globally tender with guarding in the lower abdomen and absent bowel sounds. An AXR revealed dilated loops of small bowel (fig 1). An urgent CT abdomen, requested after surgical assessment the same day, revealed dilated small bowel loops with no transition point and a small amount of free fluid in the pelvis (fig 2).

Figure 1.

Abdominal radiograph: few dilated loops of small bowel noted.

Figure 2.

CT abdomen: dilated loops of small bowel with no transition point noted.

Repeated examination later that day revealed a peritonitic abdomen. The patient underwent emergency laparotomy on day 3 of admission, and this found a 50 cm segment of ischaemic jejunum with dusky omentum overlying it. No perforation or hernias were seen; incidentally, the appendix had an enlarged tip with a faecolith. The large bowel was normal and a diagnosis of small bowel infarction was made, possibly secondary to thrombosis or embolus, as blood clots were found in the vessels of the mesentery on division. A small bowel resection with end-to-end anastomosis and appendicectomy were performed. Microscopy revealed widespread full-thickness haemorrhagic infarction of the bowel wall (fig 3); samples of the mesentery also showed extensive vascular congestion and haemorrhage. The aetiology was highly likely to be ischaemic, although no direct cause for this was apparent in the samples taken. There was no evidence of atypia or malignancy and the appendix showed acute inflammation in the mucosa. He was commenced on low molecular weight heparin and followed up in the haematology clinic upon discharge.

Figure 3.

Microscopy of the bowel wall showing widespread full-thickness haemorrhagic infarction.

DISCUSSION

Acute mesenteric ischaemia (AMI) carries a significantly high mortality rate, with some literature quoting as high as 90% mortality.¹ In AMI, sudden onset severe abdominal pain, pyrexia, vomiting, diarrhoea and bloody stools are sometimes seen.² Peritoneal findings occur late and usually only once infarction of the bowel wall has developed. Risk factors for visceral emboli include cardiac emboli (atrial fibrillation, septic emboli from valvular endocarditis), mural thrombus post myocardial infarction and structural heart defects (right-to-left shunts).² A clinical diagnosis of AMI should be borne in mind with a high index of suspicion in the presence of risk factors for thrombosis or emboli.

None of the above risk factors were present in our described patient and prior to presentation he had no past medical history of note. He also had no history of trauma prior to this episode and no signs or symptoms to suggest vasculitis. A thrombophilia screen was normal as was his echocardiogram and 24 h ECG tape. Studies for antinuclear antibodies, anticardiolipin antibodies and lupus anticoagulant were also found to be negative on follow-up. Throughout his admission his haematological markers were also within normal range (haemoglobin 16 g/dl, mean cell volume 82.5 fl, red blood cells 5.32×10¹²/l, haematocrit (ratio) 0.440, platelets 228×10⁹/l on admission), therefore making a diagnosis of polycythaemia unlikely. Other blood markers such as WCC and CRP eventually returned to normal once he recovered from surgery. Dobrinja C et al and Choudhary et al have previously described cases of idiopathic mesenteric venous thrombosis, one of which was treated successfully with bowel resection and anticoagulation.^3,4 It is important to note that a delay in diagnosis is often reported in such cases. This is due to non-specific symptoms, and also because no predisposing factors are identified.

AMI remains a diagnostic challenge despite the emergence of newer imaging techniques. Findings on plain AXR are often normal and if present (small bowel obstruction, thickened bowel walls and submucosal gas⁵) they are often late. Angiography, once a gold standard for the diagnosis of mesenteric ischaemia, now has more of a confirmatory role with the emergence of multidetector row CT.² Via CT, a diagnosis of mesenteric ischaemia can be aided by findings of bowel wall thickening, engorgement of mesenteric veins, loss or increase of bowel wall enhancement, and infarction of other abdominal organs.⁶ A study by Aschoff et al showed multidetector row helical CT using a biphasic mesenteric angiography protocol to have a sensitivity of 93% and a specificity of 100% for the aforementioned CT findings.⁷

None of the above findings were present in the CT for the described patient. Our patient developed peritonitis that suggested bowel wall infarction 5 days after he first developed symptoms, and was admitted to the medical ward with a provisional diagnosis of gastroenteritis. This led to an urgent assessment, where a diagnosis of AMI was made, within 1 h of surgical assessment. In a previous report, laparoscopy may be indicated in only selected cases of early acute mesenteric ischaemia in combination with radiological revascularisation as an alternative to conventional treatment.⁸

Even though the histopathology findings were unable to confirm a definite diagnosis, blood clots found in the mesentery during laparotomy suggest that the cause in this case was likely to be thrombotic or embolic. Thrombotic AMI is a late complication of pre-existing visceral atherosclerosis. Most patients with thrombotic AMI have atherosclerotic disease, such as coronary artery disease, peripheral arterial disease or stroke, at other sites. Embolic AMI is usually caused by an embolus of cardiac origin. The vascular occlusion is sudden, so the patients have not developed a compensatory increase in collateral flow. The superior mesenteric artery is the visceral vessel most susceptible to emboli because of its small take-off angle from the aorta and higher flow. In this patient, risk factors for atherosclerosis were absent and onset of symptoms was sudden, suggesting the likely cause would be an embolic event. Nevertheless, the cardiac causes of emboli were excluded by ECG and echocardiogram. Another possible cause of AMI is mesenteric venous thrombosis and this usually occurs in a younger age group. In this age group, patients are prone to develop blood clots, either primary or secondary. Primary mesenteric venous thrombosis occurs in the absence of any identifiable risk factor. In secondary venous mesenteric thrombosis, there are many causes, including inflammation. Interestingly, the appendix was inflamed in this patient.

Although much has been written about mesenteric ischaemia in the presence of risk factors, there is very little on those cases with no risk factors including no indication from diagnostic tests, as seen in this case report.

LEARNING POINTS

• Acute mesenteric ischaemia is an important diagnosis to make due to the high mortality rate associated with the condition.

• It is often a difficult diagnosis to make clinically, even with the aide of imaging modalities, due to non-specific symptoms.

• We feel it should be considered as part of a differential diagnosis when patients present with an acute abdomen, as early diagnosis can lead to successful outcomes.