Acute mesenteric ischemia patients are typically older and present with severe pain in the tummy, which is out of proportion to the examination. The patient subjectively describes pain in the tummy that is very severe but there is minimal tenderness elicited on physical examination. Other features will be elevated white blood cell count and acidosis on the blood result.
The most common reason for this is atrial fibrillation (irregular heartbeat), myocardial infarction (heart attack), and mural thrombus (blood clot in the artery). The most common reason for acute mesenteric ischemia is embolus, meaning a blood clot travels and blocks the circulation to the bowels; this is seen in 60% of the cases.
Classically, patients described no preceding pain in the tummy or fear of food or bloody diarrhea, and the onset of the symptoms is quite sudden.
The superior mesenteric artery is one of the three main blood vessels supplying the bowel, and the blockage is typically at the origin of the artery. If the blockage develops suddenly, there is no time to develop collateral or alternative circulation and therefore the symptoms are very severe.
Thrombotic etiology is the second most common reason and typically affects patients who have been having symptoms for a while. This is seen in 30% of the cases. This happens because the circulation to the bowels was compromised for a long time and then suddenly the blockage became complete.
The third most common cause of acute mesenteric ischemia is nonocclusive etiology (NOMI). Arterial circulation to the bowel is not blocked but the arteries go into spasm and cause contraction, limiting blood supply to the bowel. Patients who are critically ill and have suffered loss of blood volume and are hypertensive typically have this presentation. Other reasons might be digoxin, which is a cardiac medication, or cocaine toxicity. Management in this case focuses on supportive treatment and sometimes injection of a medicine known as papaverine, which can cause blood vessels of the bowels to dilate.
In all cases of mesenteric ischemia, a blood-thinning medication known as heparin is started while the cause is investigated. Diagnosis is most commonly by CT angiogram. This is a test that involves the patient going into a CAT scan machine, which is shaped like a doughnut and takes about five minutes. Intravenous contrast dye is also rapidly administered through a peripheral intravenous catheter.
Management of acute mesenteric ischemia mainly revolves around rapid diagnosis with CT angiogram, supportive treatment like starting IV heparin drip (blood thinner medication), and — if there is concern that bowel might be dead or dying — taking the patient to the operating room for explorative surgery. Fixing the circulation before any kind of bowel surgery is done is the usual recommendation. The patient may need to be brought back to the operating room in 24 to 48 hours for a second look to make sure that any bowel that is compromised is not left in the belly.
There are various methods of restoration of circulation to the superior mesenteric artery like embolectomy, performing a bypass procedure, placing a stent in the superior mesenteric artery, and sometimes utilizing a hybrid management approach that is a combination of open and endovascular means.
Superior mesenteric artery is the main artery supplying the midgut. Blockage of this artery causes mesenteric ischemia.