Chronic mesenteric ischemia

Chronic mesenteric ischemia ("abdominal angina")

Slowly progressing visceral artery obstruction over a long period of time may lead to the development of collateral circulation, without being accompanied by pronounced disorders and without manifesting clear symptoms. This is confirmed by pathologists' data.

There are two groups of factors that lead to chronic visceral circulation disorders:

1. intravasal;
2. extravasal.

Among intravascular causes, obliterating atherosclerosis and nonspecific aortoarteritis are in first place. Less common are hypoplasia of the aorta and its branches, aneurysms of unpaired visceral vessels, and fibromuscular dysplasia.

Extravasal cause - compression of unpaired visceral branches by the falciform ligament of the diaphragm or its medial leg, neuroganglionic tissue of the solar plexus, tumors of the tail of the pancreas or retroperitoneal space. In this case, the celiac trunk is most often subjected to compression.

Of all the reasons listed above, the main one is atherosclerosis.

Summarizing numerous studies and his own observations, A. Marston (1989) gives the following modern understanding of chronic intestinal ischemia:

1. The main cause is atherosclerosis of the visceral arteries.

The incidence of lesions increases with age. In most cases, such lesions are mild and "critical stenosis" is rare, occurring in about 6% of cases;

2. the frequency of lesions of the celiac trunk and superior mesenteric artery is approximately the same, while lesions of the inferior mesenteric artery are observed less frequently;
3. the macroscopic appearance of the intestine does not depend on the presence of arterial obstruction;
4. No relationship was found between the degree of arterial occlusion detected at autopsy and gastrointestinal symptoms observed during life.

Thus, stenosis and occlusion of the visceral arteries in their chronic damage is a more frequent finding of pathological anatomical rather than clinical examination. The difficulties of early detection of chronic intestinal ischemia can be explained by the fact that, due to compensatory mechanisms that redistribute blood flow in the intestinal wall, intestinal functions, including absorption, remain normal almost until the moment when the damage becomes irreversible. Collateral circulation contributes to the fact that even with complete occlusion of the visceral arteries, there are no symptoms of vascular insufficiency in the intestine. However, as the arterial inflow continues to decrease, ischemia of the muscular layer of the intestine and associated pain occur, since the blood flow becomes insufficient to ensure increased peristalsis caused by food intake. Blood circulation in the mucous membrane remains normal for some time and the absorption and excretion function of the intestine is not impaired. As the process progresses further, blood flow decreases below the level necessary to protect the mucous membrane from bacterial damage, and focal or massive infarction develops.

Of great practical importance is the classification of chronic mesenteric ischemia by B.V. Petrovsky et al. (1985), according to which three stages are distinguished:

• / stage - relative compensation. At this stage, the dysfunction of the gastrointestinal tract is insignificant and the disease is detected accidentally during examination of patients for some other reason;
• // stage (subcompensation) - characterized by severe intestinal dysfunction, abdominal pain after eating;
• /// stage (decompensation) - manifested by intestinal dysfunction, constant abdominal pain, progressive weight loss.

A. Marston identifies the following stages of development of intestinal ischemia:

• 0 - normal condition;
• I - compensatory arterial lesion, in which there is no disturbance of blood flow at rest and after eating and there are no symptoms;
• II - arterial damage progresses to such an extent that blood flow at rest remains normal, but reactive hyperemia is absent. This is evidenced by pain after eating;
• III - insufficient blood supply with decreased blood flow at rest. A condition similar to pain at rest in ischemia of the extremities;
• IV - intestinal infarction.

Symptoms of intestinal ischemia:

The first clinical manifestations of chronic mesenteric ischemia appear in stage II according to the classification of B.V. Petrovsky.

The leading clinical symptoms are the following:

1. Abdominal pain. Pain in chronic mesenteric ischemia is often referred to as "abdominal toad", "abdominal intermittent claudication". Its main features are:

• clearly associated with food intake, occurs 20-40 minutes after eating;
• does not have a clear localization (can be felt in the epigastrium, around the navel, in the projection of the large intestine);
• is cramping and spastic in nature;
• relieved by nitrates and antispasmodics in the initial period;
• significantly increases with the progression of the pathological process in the mesenteric arteries.

2. Intestinal dysfunction. Chronic intestinal ischemia leads to its dysfunction, which is manifested by pronounced flatulence and rumbling in the abdomen after eating, constipation; with a long course of the disease, diarrhea appears.
3. Auscultatory signs of abdominal ischemia. Characteristic signs of mesenteric ischemia are detected during auscultation of the abdomen:

• systolic murmur at a point located midway between the xiphoid process and the navel (projection of the superior mesenteric artery);
• increased intestinal peristaltic sounds after eating.

4. Progressive weight loss of patients. In cases of severe mesenteric ischemia, a decrease in body weight is observed.
   This is due to the patients' refusal to eat (since eating causes significant abdominal pain) and a violation of the intestinal absorption capacity.
5. Aortoangiography data. Aortoangiography allows to verify the diagnosis of mesenteric ischemia (narrowing and prestenotic dilation, deformation of the superior or inferior mesenteric artery are detected).

Auscultation of the abdomen often reveals symptoms characteristic of chronic ischemia: systolic murmur, determined at a point located midway between the xiphoid process and the umbilicus, which corresponds to the location of the superior mesenteric artery, and increased intestinal noises after eating.

Aortoangiography findings in this pathology may include stenosis and prestenotic dilation, occlusion and deformation of the visceral arteries.

There is no effective conservative treatment that can stop the progression of the disease. Consequently, there is a constant threat of acute visceral blood flow disorder. Taking this into account, surgeons dealing with the problem of chronic ischemia in our country recommend surgical treatment at stages II (subcompensation) and III (decompensation). As for stage I (compensation), it is recommended to perform blood flow correlation in visceral branches only in cases where patients are operated on for damage to the abdominal aorta or its other branches, since in this case hemodynamic conditions in the visceral branches may worsen. In case of well-developed collateral blood flow against the background of angiographically detected damage to the visceral arteries, it is advisable to postpone the operation.

Surgical intervention is resorted to only in cases where patients continue to experience pain in the presence of established arterial obstruction, as well as when a complete clinical examination excludes any other genesis of the symptoms.

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