Acute superior mesenteric artery infarction

　　The main causes of most acute superior mesenteric artery infarction are vascular lesions and insufficient blood perfusion, followed by bacterial infection. The above causes can lead to acute superior mesenteric artery ischemia, thrombosis, or embolism. The specific pathogenic mechanism is as follows:

　　1. Vascular disease
　　Mainly atherosclerosis, arterial embolism, or thrombosis. In addition, diseases such as multinodular arteritis, rheumatoid arthritis, diabetes, etc., also concurrently complicate small vessel arteritis. The lesions often involve the main trunk and branches of the superior mesenteric artery, sometimes occurring in small arteries, and are most likely to occur within 2 cm of the opening of the abdominal aorta. The superior mesenteric artery branches off obliquely from the abdominal aorta, so emboli in the systemic circulation are极易 enter this artery to form an embolism.

　　2. Insufficient blood perfusion
　　When the lumen of atherosclerosis patients is narrowed, although the blood supply can still maintain the normal activity of the intestinal tract, the reserve capacity has been reduced. Any cause of blood pressure drop may lead to insufficient blood supply and infarction, especially in patients with diseases such as aortic dissection and systemic lupus erythematosus, who are more prone to occur.

　　3. Bacteria and bacterial toxins
　　Under normal circumstances, the intestinal flora maintains a dynamic balance. When intestinal ischemia occurs and the defense ability of the intestinal wall decreases, bacteria invade the intestinal wall, which can cause pseudomembranous colitis, postoperative colitis, acute necrotizing colitis, and acute hemorrhagic colitis, etc. Animal experiments show that if antibiotics are added after intestinal ischemia, the rate of shock in animals decreases.

　　Superior mesenteric artery infarction is mostly caused by embolism from cardiac source, or atherosclerosis secondary to thrombus blocking the lumen, ultimately leading to infarction of the corresponding tissue. The disease may be complicated by paralytic ileus and toxic shock in the late stage.

　　The clinical manifestations of superior mesenteric artery infarction vary due to the location, extent, and collateral circulation of the infarction. Abdominal pain is the most common symptom, often sudden, diffused periumbilical pain, with the patient's expression extremely painful, and analgesics are often ineffective. It may be accompanied by vomiting, diarrhea (often bloody diarrhea), difficulty breathing, and confusion. If accompanied by frequent defecation, it is a typical symptom of acute ischemic mesenteric infarction, and ischemic mesenteric infarction rarely has the desire to defecate or acute defecation.
　　In the early stage of the disease, the abdominal signs and symptoms are obviously inconsistent with the disease, the abdominal muscles are not tense, and the tenderness is not obvious, the bowel sounds can be normal or hyperactive. With the aggravation of ischemia, abdominal distension is significant, bowel sounds weaken, and muscle tension, tenderness, and rebound pain appear, with serositis and perforative peritonitis as its characteristics. In addition, fever, tachycardia, hypotension, increased white blood cell count, and nuclear left shift may be accompanied.

　　To prevent superior mesenteric artery infarction, it is necessary to actively treat the primary disease, such as valvular heart disease, myocardial infarction, and bacterial endocarditis, etc., and prevent the formation of emboli or thrombi that lead to the disease.

　　In the laboratory examination of superior mesenteric artery infarction, the white blood cell count often exceeds 20×10^9/L, serum amylase increases, and CPK continuously increases with the progression of the disease, gradually recovering after 72 hours; serum lactate dehydrogenase (LDH) and its isoenzyme ratio, and serum inorganic phosphorus are all elevated. The auxiliary clinical examinations mainly include:

　　1, Abdominal X-ray examination Abdominal X-ray examination can be seen in the early stage of small intestinal gas; when the condition develops to intestinal paralysis, small intestinal and colonic distension, intestinal wall edema and thickening can be seen; when intestinal necrosis occurs, intestinal cavity gas leaks into the intestinal wall, accumulates under the serosa, and a light transmittance band or light halo can be seen on the flat film. Sometimes, gas shadows can also be seen in the portal vein.

　　2, Angiography For patients suspected of acute mesenteric ischemia, flat films have excluded other acute abdominal conditions. Regardless of abdominal signs, early angiography should be performed. Because this not only can differentiate whether the occlusion of large blood vessels is caused by thrombosis or embolism, but also diagnose non-occlusive ischemia, the degree and extent of vascular stenosis.

　　3, CT examination This examination can directly display blood clots in the intestinal wall and blood vessels, which is superior to X-ray films and barium meal examination.

　　4, Doppler ultrasound This examination can measure the blood flow of the portal vein and superior mesenteric vein, which has certain diagnostic value for judging the formation of thrombi in the blood vessels.

　　5, Radioisotope examination Monoclonal antibodies labeled with radioactive indium or technetium to platelets, after injection into the human body, can be used for γ-photography to display the ischemic area of acute mesenteric occlusion. Currently, this technology is gradually used in clinical practice and is expected to have a good development prospect.

　　In addition to conventional treatment, dietary requirements should be different according to different symptoms, and specific dietary standards should be formulated based on specific diseases. Please consult a doctor for specific advice.

　　The general treatment for acute superior mesenteric artery infarction includes fasting, gastrointestinal decompression, intravenous fluid replacement, and maintaining water and electrolyte balance. For patients highly suspected of mesenteric artery ischemia, after excluding other acute abdominal conditions, whether or not surgery decides to perform laparotomy. It should also be done as soon as possible to perform selective mesenteric artery angiography. Once the diagnosis is clear, first give mesenteric artery resuscitation, actively improve insufficient mesenteric perfusion, and provide emergency surgical treatment. Shock patients should be corrected in a timely manner. Blood transfusion and the use of broad-spectrum antibiotics are beneficial to reduce intestinal ischemia and alleviate endotoxemia. Active treatment of the primary disease, such as correcting arrhythmias, congestive heart failure.