31st July 2023

Acute Mesenteric Ischaemia

Describes sudden-onset ischaemia of the small bowel secondary to hypoperfusion of the superior mesenteric artery (SMA) or its branches. The hypoperfusion can be secondary to arterial thrombosis, arterial embolism or non-occlusive ischaemia due to poor cardiac output.

The predisposing factors, and signs and symptoms, of all syndromes of ischaemia to the lower gastrointestinal tract are similar and are summarised in Table 1. However, the management and prognosis vary greatly; therefore, it is important to differentiate the various types.

Table 2: Common risk factors and clinical features to both mesenteric ischaemia and ischaemic colitis

The sudden-onset, severe pain is usually constant, central within the abdomen and responds poorly to analgesia. Typically, there are no other abdominal signs. Along with a raised serum lactate, there may be an increased serum amylase and leucocytosis.

The diagnosis is usually made on CT abdomen and pelvis with contrast, though this should not delay laparotomy if there is high suspicion for the condition. The CT may reveal gas in the intestinal wall or portal vein.

The general surgery team will typically organise an emergency laparotomy, and the prognosis is especially poor if the operation is delayed. The bowel is assessed for viability and the necrotic bowel is removed. Endovascular thrombolysis or thrombectomy may be an option in a minority of patients. Patients will usually remain on long-term anticoagulation.

Complications include peritonitis, with or without sepsis, due to bacterial translocation across the necrotic bowel. Therefore, broad-spectrum antibiotics are usually commenced, with a regimen that will also target anaerobic bacteria (e.g., ceftriaxone + metronidazole). Mortality rate is high, estimated at around 50%.

Acute bowel ischaemia leading to necrosis

Image Source: Wikimedia Commons (2008). Intestinal Obstruction, Licensed under a creative commons licence. Available for free at: https://commons.wikimedia.org/wiki/File:Intestinal_Obstruction.JPG (Accessed: 28 June 2023).