OVERVIEW
Nonocclusive mesenteric vascular ischemia is a form of acute intestinal ischemia caused by spasm of the superior mesenteric artery with a high mortality rate. It is characterized by atypical clinical presentation, diagnostic difficulties, and comorbidities with other serious systemic diseases. The earliest definition of nonocclusive mesenteric vascular ischemia was from the finding at autopsy that the patient had necrosis of the small bowel without significant occlusive changes in the arteries or veins. Studies of mesenteric circulation have shown that mesenteric vasoconstriction, tissue hypoxia, and ischemia-reperfusion injury can cause nonocclusive mesenteric ischemia.
Etiology
The key to nonocclusive mesenteric vascular ischemia is spasm of the superior mesenteric artery, which is associated with a persistent state of reduced cardiac output and hypoxia, and is an end-stage manifestation of diseases such as sepsis, congestive heart failure, arrhythmia, acute myocardial infarction, and severe blood loss.
Symptoms.
It may be similar to acute arterial or venous mesenteric occlusion, and is more common in the elderly.
1. Early manifestations
Superior mesenteric artery occlusion occurs slowly over several days and may be preceded by weakness and abdominal discomfort.
(1) Abdominal pain The abdominal pain of non-occlusive mesenteric ischemia is less severe than that of acute superior mesenteric artery embolism or thrombosis, and the degree, nature and location of the pain varies, with 20% to 25% of patients having no abdominal pain.
(2) Abdominal distension and gastrointestinal bleeding Abdominal distension and gastrointestinal bleeding without obvious cause may be the early manifestation of non-occlusive mesenteric ischemia and intestinal necrosis.
2. Intestinal necrosis
Intestinal necrosis is characterized by sudden severe abdominal pain, vomiting, sudden drop in blood pressure and tachypnea. Fever, watery diarrhea or bloody stools, weakened bowel sounds, and later disappear. Localized or widespread tenderness, rebound pain and abdominal muscle tension in the abdomen suggests total intestinal wall necrosis and poor prognosis.
Examination
Diseases with decreased visceral circulation that present with unexplained abdominal symptoms and signs should raise a high suspicion for the possibility of this disease.
1. Medical history
People with non-occlusive mesenteric vascular ischemia are at high risk if they have a history of: ① acute myocardial infarction with shock, congestive heart failure, and arrhythmia; ② burns with hypovolemia; ③ abscess, pancreatitis; ④ hemorrhagic shock; ⑤ use of adrenergic α-receptor excitatory drugs and digitalis drugs that have the function of constricting the visceral vasculature.
2. Clinical manifestations
Sudden onset of severe abdominal cramps, accompanied by watery diarrhea or bloody stools, fever, diminished or absent bowel sounds; abdominal signs include localized or widespread pressure, rebound pain and abdominal muscle tension.
3.Auxiliary examination
Superior mesenteric artery angiography reveals stenosis at the beginning of most branches of the superior mesenteric artery, irregular spasmodic changes in the morphology of the intestinal canal, and poor vascular filling within the intestinal wall.
Diagnosis
Since non-occlusive mesenteric vascular ischemia (NOMI) lacks specific clinical manifestations in its early stages, the key to early diagnosis of NOMI is to raise awareness of the disease. The following points can be used as the basis for diagnosis:
1. advanced age, previous hypertension, coronary heart disease, atrial fibrillation and other cardiovascular diseases;
2. admission with insufficient cardiac output such as shock, hypotension, severe anemia and congestive heart failure;
3. previous long-term application of vasoconstrictor drugs such as digitalis and alkaloids and long-term injection of diuretic drugs such as tachycardia.
Under the premise of the above etiological factors, if the patient has persistent abdominal pain, blood in stool, vomiting of coffee-like contents and intestinal obstruction, the possibility of NOMI should be considered, and then it is necessary to carry out imaging tests or even angiography to further clarify the diagnosis.
Treatment
1. Non-surgical treatment
After the diagnosis is clarified by arteriography, corresponding measures should be taken to prevent the occurrence of intestinal necrosis.
(1) Improve cardiac function Firstly, improve cardiac function and maintain hemodynamic stability, use vasoconstrictor drugs and digitalis drugs with caution, use vasodilator drugs to reduce the preload and afterload of the heart, and relieve vasospasm.
(2) Vasodilatation Through arteriographic catheter, input of opioid can effectively dilate blood vessels and improve blood supply. At the same time, observe the systemic and local clinical symptoms, and if necessary, repeat arteriography to observe the blood flow of the superior mesenteric artery.
(3) Actively treat the primary disease.
2. Surgical treatment
If the patient’s condition cannot be relieved, and there are leukocytosis, gastrointestinal bleeding, and gas accumulation in the intestinal lumen, emergency caesarean section surgery is needed. The purpose of the surgery is to determine the vitality of the affected intestinal tubes and to remove the possible necrotic intestinal segments. Intraoperatively, necrotic bowel can be seen with grayish color, dilated lumen, edema of the bowel wall, and loss of peristalsis. If the necrotic bowel is clearly defined, one-stage intestinal resection and intestinal anastomosis is feasible, otherwise, the necrotic bowel can be placed externally.
3. Postoperative treatment
Prevent infection, anticoagulation and supportive therapy should be given after operation.