Tricky gut ischemia, the uselessness of lactate, and the importance of clinical suspicion

You are called to see Ms A, an 80 year old woman on the surgical ward, due to worsening abdominal pain and tachycardia. She was admitted 8 hours ago with the same abdominal pain and diarrhea and had a CT abdomen, which the radiology registrar has provisionally reported as showing non-specific pericolonic fat stranding. She has been treated as an infectious colitis. She has a history of ischemic heart disease, atrial fibrillation and claudication. Examination of her abdomen shows diffuse tenderness but no peritonism.

You call the surgical registrar to express your concern this lady might have ischemic gut. He informs you he is reassured by the CT findings, the lack of peritonism and the normal lactate, which you had decided to check because you have recently heard about the association between gut ischemia and elevated lactate. When you arrive at work the next morning you discover that overnight she had become septic, spiked her lactate to 8 and been taken for a laparotomy, where extensively necrotic bowel was found. She was palliated.

Ischemic gut is one of those diagnoses that is always tricky to make, as there is no lab test to help you and the examination findings can be non-specific, although “pain out of proportion to the exam” is what you might find in the textbooks.  Age confers an exponentially increasing risk, and past the age of 75 it becomes more likely than appendicitis or ruptured AAA (1). This is a fact which I certainly hadn’t appreciated and I suspect many people don’t, given the frequency with which we query the latter two on CT requests and the infrequency with which we query ischemic gut.

The first point to make abundantly clear is that peritonism is a late sign of extensive bowel necrosis so is not reassuring. The same applies to the finding of portal venous gas on an abdominal Xray, pictured below (2). The whole point is to diagnose the condition early enough that you can do something about it (either open or endovascular revacularisation). By the time these signs develop, the proverbial train has left the station.

portal venous gas

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