Colon vasodilation

Introduction to colonic vasodilation Colonic vasodilatation is a group of colonic vascular malformations. It is composed of benign non-neoplastic dilated vascular plexus, also known as colonic vascular dysplasia, colonic vasodilation, and colonic arteriovenous malformation. Margulis first passed the mesenteric arteriovenous vein in 1960. The angiography confirmed the presence of colonic vasodilatation, and the related reports gradually increased. In recent years, the disease has been found to be one of the main causes of lower gastrointestinal bleeding, especially in elderly patients, accounting for about 4% of all lower gastrointestinal bleeding. With the wide application of fiberoptic colonoscopy, reports of vasodilation and colonic vasodilation in patients with portal hypertension have become more and more. Chen et al reported that approximately 50% of patients with portal hypertension are associated with colonic vasodilation. basic knowledge The proportion of illness: 0.003% Susceptible people: no specific population Mode of infection: non-infectious Complications: shock iron deficiency anemia

Cause of colonic vasodilation

Acquired vascular malformations (75%):

The most common, accounting for more than 90% of all colonic vasodilatation, is the most common cause of lower gastrointestinal bleeding, more than the lower gastrointestinal bleeding caused by colon tumor and colonic diverticulitis, the lesions are mostly single, thin Wall vascular composition, without inflammation and fibrosis, although more common in the right colon, can occur in the left colon and small intestine, occasionally reported in the esophagus, stomach, duodenum and empty, ileum, vascular lesions Involving other internal organs, although more common in the elderly, the disease can also occur in people of any age, most of the bleeding occurs in patients with hypertension, arteriosclerosis, diabetes, cirrhosis, portal hypertension, chronic obstructive pulmonary disease and Elderly people with chronic kidney disease.

Congenital arteriovenous malformation (15%):

Originated in young people, the lesions are diffuse, but non-invasive, composed of abnormal arteries and veins, usually occurring in the small intestine, multiple, or in the colon, similar to hereditary hemorrhagic telangiectasia, but not With systemic manifestations of Osler-Rendu-Weber syndrome (genetic hemorrhagic telangiectasia), these congenital lesions are sometimes accompanied by Tumer syndrome (expressed as short body, gonadal dysplasia, and neck deformity).

Hereditary telangiectasia (10%):

Most have a family history, intestinal bleeding rarely occurs before the age of 35, can occur in any part of the gastrointestinal tract, but the most common ileum and right colon, often multiple, scattered distribution, in the oropharynx and tongue mucosa Typical telangiectasia can be seen. Other organs that are often invaded include the kidney, liver, brain and lungs, capillary, arterioles and venules. The elastic fibers and muscle fibers are weak, making the lesion vulnerable to injury. After a large amount of bleeding, this situation can be more serious due to the patient's thrombocytopenia. The typical endoscopic manifestation of telangiectasia is small red mucosal lesions, flat oval, lightly pressed into white, partially visible Spider web-like small vascular network.

Pathogenesis

Pathology

Colonic vasodilating lesions occur in the right colon, especially the cecum. The literature reports that about 75% are distributed in the cecum and ascending colon, 12% in the transverse colon, 12% in the left colon, and a few lesions in the digestive tract. The site, including the stomach, duodenum, jejunum and ileum, is mostly scattered in patients with portal hypertension. In other patients, most of the lesions are single, except for portal hypertension, about 60%. Patients may also be associated with cardiovascular, pulmonary and renal diseases, without skin or visceral hemangioma lesions. The typical pathological manifestations of colonic vasodilator lesions are difficult to detect on ordinary formaldehyde-fixed specimens that have not been specially treated. In particular, early lesions, Boley reported that in the lesions confirmed by angiography, the rate of common pathological examination was only about 30%.

Visual observation showed that the early and lighter lesions were intact and there was no special manifestation; in the middle and late stage patients, the mucosa showed a coral-like change in the lesion, and the varicose veins were radially distributed, and collected into a coarse central penetrating vein toward the center; Local mucosal erosion can be seen in patients with severe lesions.

Histological examination showed that the lesions were mostly 0.1 to 1 cm in diameter, and the mucosa of the lesion was intact. There was no cell proliferation and vascular sprouting in the lesion. The most common and obvious early abnormality was the thinly-walled blood vessels that were obviously dilated and distorted under the mucosa. The vast majority have only the endothelial cell layer, and occasionally a small amount of smooth muscle, which is similar in structure to the dilated vein. In the middle and late stage, patients can see a vascular mass composed of localized veins or dilated capillaries in the submucosa. The lesions, the number of submucosal dilated veins increased, deformed, blood vessels through the mucosal muscle layer and invasion of the mucosa, when the lesion is severe, the mucosa can be replaced by a distorted and dilated vascular mass.

There are two common methods for the special treatment of specimens, one is injection with silicone gel; the other is injection with silicone rubber. After excising the specimen, the blood in the blood vessels of the specimen is rinsed with heparin saline, and any one of the above is injected. Substance, after the coagulation is solidified, observing the mucosal surface of the specimen and observing the tissue section of the specimen, it is easier to see the dilated vascular plexus.

2. Pathogenesis

The mechanism of type I colonic vasodilation is related to the obstruction of colonic venous return caused by acquired factors, submucosal arteriovenous short circuit, and the venous return obstruction includes two reasons: submucosal venous return obstruction and portal venous return obstruction.

Bolev believes that the occurrence of colonic vasodilation is associated with repeated increases in intracolonic pressure. The pressure in the colon is elevated or the smooth muscle of the intestinal wall is in a contracted state, so that the wall of the blood vessel that passes through the smooth muscle is compressed, and the submucosal venous return of the intestinal wall is blocked. The increase of venous pressure, combined with the lesions and weakness of the vein wall itself, leads to varicose veins and dilatation. At the same time, due to venous vasodilation, the anterior capillary dysfunction of the capillaries leads to the formation of tiny arteriovenous fistulas, which further increase the venous pressure. Vasodilation, according to Laplace's laws of physics: the pressure on the wall of a spherical object is proportional to the product of the square of the radius of the sphere and the pressure in the cavity, ie the pressure on the wall is proportional to the square of the radius of the sphere, the cecum and the near The ascending colon is the largest part of the whole colon. When the pressure in the colon is increased for some reason, the pressure on the intestinal wall near the cecum and ascending colon is the greatest, which may explain the coronary vasodilation. The cause of the proximal end of the right colon.

The occurrence of type II and III colonic vasodilatation is generally thought to be associated with developmental defects in the congenital intestinal wall and vessel wall.

Colonic vasodilation prevention

The incidence of recurrent bleeding after surgery for colonic vasodilation is about 4%, mainly due to missing lesions, especially lesions located in the terminal ileum or other parts of the colon.

Complications of colonic vasodilation Complications, iron deficiency anemia

Hemorrhagic shock can occur in a large number of bleeding in a short period of time; in the long-term, repeated small amount of bleeding is mainly complicated by iron deficiency anemia.

Symptoms of colonic vasodilation Common symptoms Varicose sclerosing iron deficiency anemia shock colonic diverticulum

The vast majority of patients with colonic vasodilatation have no clinical symptoms. Only a small number of patients have sudden, intermittent or recurrent painless lower gastrointestinal bleeding as a clinical feature. Welch reported that among 72 patients with lower gastrointestinal bleeding, 43 For example, due to colonic vasodilatation, Boley reported 32 cases of lower gastrointestinal bleeding caused by colonic vasodilatation, 23 of which were more than 2 times. Due to the amount of bleeding per episode, bleeding rate and lesion location, clinical manifestations There are also significant differences. The lesions are located at the proximal end of the colon. Most of the patients with more bleeding have maroon or tar-like stools; the lesions are located in the left colon, and patients with more bleeding can be bright red; a small number of patients with massive bleeding in the short term may Hemorrhagic shock occurs in acute hemorrhage; patients with long-term repeated small amount of bleeding mainly present with chronic iron deficiency anemia.

In the lower gastrointestinal bleeding caused by colonic vasodilatation, most patients have less bleeding per episode, and bleeding is self-limiting. 80% to more than 90% of bleeding can be stopped without special treatment, but it can recur frequently afterwards. .

Nearly half of patients with lower gastrointestinal hemorrhage caused by colonic vasodilation have a history of coronary heart disease or aortic stenosis, and about one third of patients have colonic diverticulitis, which reflects colonic vasodilation as an elderly The disease also suggests that the occurrence of bleeding may be related to cardiovascular disease, arterial hypertension, and local colonic inflammation around the dilated blood vessels.

For patients with a history of recurrent lower gastrointestinal bleeding or chronic iron deficiency anemia, digestive tract tumors, esophageal varices and gastric mucosal hemorrhage, colonic diverticulitis, colonic hemangioma, etc. caused by gastrointestinal bleeding were excluded by various tests. After common causes, consideration should be given to the possibility of colonic vasodilatation, especially in middle-aged and elderly patients over 60 years of age and patients with cirrhosis and portal hypertension.

Selective mesenteric angiography is an effective and accurate clinical diagnosis method with an accuracy rate of 75% to 90%. However, because this examination is an invasive examination, there is a certain risk to elderly patients, and in recent years, colonic fibroscopy The popularity of the application and the accumulation of application experience, more clinicians tend to determine the diagnosis by fiberoptic colonoscopy, for lesions with lower gastrointestinal active bleeding, and bleeding rate of more than 0.1ml per minute, radionuclide scanning It is also an effective method of examination. Colonic sputum double contrast examination can help to eliminate bleeding caused by colon tumors, colonic diverticulitis and the like.

Examination of colonic vasodilation

Laboratory tests have no diagnostic value for this disease, and can help diagnose the primary disease and complications.

Blood routine

There may be performance of iron deficiency anemia.

2. Blood biochemistry

The change of indicators is related to the primary disease, such as abnormality of blood lipid metabolism in patients with arteriosclerosis; abnormal indicators of blood glucose metabolism in diabetic patients; abnormal plasma protein metabolism in patients with portal hypertension and advanced liver disease.

3. Liver function and lung function

Patients with cirrhosis, portal hypertension or chronic obstructive pulmonary disease may have abnormal liver function or lung function.

1. Colonic gas sputum double contrast

Because the lesions of colonic vasodilatation are confined to the submucosa, and the lesions are usually less than 1 cm, only about 15% of patients have scattered small colonic mucosal erosion lesions or small ulcers during colonic gas angiography. Most patients No abnormal findings, the main purpose of double contrast angiography of the colon is to exclude other gastrointestinal lesions, such as colon tumors, diverticulum and so on.

2. Mesenteric angiography

The typical manifestation of colonic vasodilation in mesenteric angiography is the delayed venous emptying of the contrast agent at the lesion site and the visible vascular clusters. The vascular cluster is most prominent in the angiographic arterial phase, mostly located at the end branch of the ileal artery. , characterized by oval clusters of blood vessels (Fig. 3), the intravascular contrast agent is slowly evacuated, and the dilated veins in the colon wall are still visible in the venous phase, suggesting that there is an expanded venous plexus under the mucosa accompanied by arteriovenous malformations. In the case of arteriovenous fistula, due to the formation of arteriovenous short circuit, venous filling can be seen in the early stage (4 to 5 s).

In patients with colonic vasodilatation with acute hemorrhage, in addition to the above manifestations, contrast agent spillage into the intestinal lumen can be observed in the lesion, which is characterized by persistent persistent amorphous shadows around the vascular cluster.

3. Fiber colonoscopy

In recent years, fiberoptic colonoscopy has been increasingly used in the diagnosis of colonic vasodilatation. This method can be used to confirm the results of mesenteric angiography and to exclude bleeding caused by other causes, such as digestive tract tumors. Can be used for biopsy and treatment of lesions, Salem et al. compared the results of mesenteric angiography and fiberoptic colonoscopy in 56 cases of colonic vasodilation, and found that 88% of the results are consistent, in addition, fiberoptic colonoscopy is often Multiple microscopic lesions that are difficult to detect by mesenteric angiography can be found. However, the degree of cleanliness of bowel preparation for fiber colonoscopy has a high level of experience.

The endoscopic findings of colonic vasodilator lesions are strongly related to the extent of the lesion. Because the usual lesions are located under the mucosa and the lesions are small, the mucosa is not obvious in most patients with mild disease. Endoscopy is difficult to detect. Vascular lesions, when dilating blood vessels invade the mucosa, typical flat or slightly elevated red vascular plaques can be seen in the lesions. Vessel networks with spider-like or coral-like distribution can be seen in the spots. Local mucosal congestion of the lesions is easy. In patients with bleeding or active bleeding, a colonoscopy can see a bleeding point at the site of the bleeding, with dilated vascular spots around it.

Although it is possible to perform biopsy of the lesion by fiberoptic colonoscopy, it may cause bleeding, so it should be cautious. In addition, it should be noted that the false positive of fiber colonoscopy results, the interpretation of the results need to be related to the recent gastrointestinal bleeding. The combination of medical history and mesenteric angiography results.

4.99mTc labeled red blood cell scan

Compared with fiberoptic colonoscopy and mesenteric angiography, 99mTc-labeled red blood cell scan has greater advantages in diagnosing bleeding from colonic vasodilatation. This test is rapid, non-invasive, does not require any bowel preparation, and requires bleeding rate. Lower, mesenteric angiography diagnosis of gastrointestinal bleeding generally requires bleeding rate of 1 ~ 2ml per minute, and 99mTc labeled red blood cell scanning only need to bleed at a rate of 0.1ml per minute or more.

Diagnosis and differentiation of colonic vasodilation

The disease should be differentiated from digestive tract tumors, esophageal varices and gastric mucosal hemorrhage, colonic diverticulitis, and colonic hemangioma.

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