Colonic angiectasia

　　I. Etiology

　　The occurrence of colonic varices is related to factors such as hereditary telangiectasia, congenital abnormal formation of arteries and veins, vascular sclerosis, and increased intracolonic pressure. According to the characteristics of angiography, age of onset, and family history, colonic varices can be divided into three types:

　　1. Type I

　　Acquired vascular malformation. It is the most common, accounting for more than 90% of all colonic varices, and is the most common cause of lower gastrointestinal bleeding, more than that caused by colonic tumors and colonic diverticulitis. The lesions are usually solitary, composed of thin-walled vessels, and do not accompany inflammation and fibrosis. Although it is more common in the right half of the colon, it can also occur in the left half of the colon and small intestine. Occasionally, it has been reported to occur in the esophagus, stomach, duodenum, and jejunum and ileum, with vascular lesions not affecting other visceral organs. Although it is more common in the elderly, it can also occur in people of any age. The bleeding from the lesions mostly occurs in the elderly with hypertension, arteriosclerosis, diabetes, liver cirrhosis, portal hypertension, chronic obstructive pulmonary disease, and chronic kidney disease.

　　In recent years, many clinical studies have confirmed that the occurrence of colonic varices is also related to portal hypertension and obstruction of portal venous return. The causes of portal hypertension include liver cirrhosis caused by various reasons, such as post-hepatitis cirrhosis, schistosomal cirrhosis, and alcoholic cirrhosis; obstruction of the portal venous system caused by various reasons, such as mesenteric venous inflammation and obstruction caused by acute and chronic pancreatitis, splenic vein thrombosis, and mesenteric subvenous obstruction caused by colon surgery. Endoscopic examination results show that the incidence of colonic varices in patients with liver cirrhosis is 45% to 62%, and the incidence in patients with liver cirrhosis and ascites is significantly higher than that in patients without ascites, the former being 63% and the latter only 18%, suggesting that the occurrence of colonic varices may be related to the progression of liver cirrhosis, but clinical research results on this are still controversial, thus the relationship between colonic varices and portal hypertension still needs further study to clarify.

　　2. Type II

　　Congenital arteriovenous malformation. It originates in young adults, and the lesions are often diffuse but non-invasive, composed of abnormal arteries and veins. They usually occur in the small intestine, are multiple in nature, and can also occur in the colon. Similar to hereditary hemorrhagic telangiectasia, but without the systemic manifestations of Osler-Rendu-Weber syndrome (hereditary hemorrhagic telangiectasia). These congenital lesions may also be associated with Turmer syndrome (manifested as short stature, incomplete gonadal development, and webbed neck deformities).

　　3. Type III

　　Hereditary telangiectasia. Most of them have a family history of inheritance. Gastrointestinal bleeding rarely occurs before the age of 35 and can occur at any part of the gastrointestinal tract, but the ileum and the right half of the colon are most common, often multiple and scattered. Typical telangiectasia can be seen in the oral pharynx and tongue mucosa. Other organs frequently involved include the kidney, liver, brain, and lung. The weakness of elastic fibers and muscle fibers in the walls of capillaries, small arteries, and small veins makes the lesion site prone to massive bleeding after injury, which can be made more severe by the patient's thrombocytopenia. The typical endoscopic manifestation of telangiectasia is small red mucosal lesions,呈扁平卵圆形, slightly pressed to turn white, with a local fine vascular network resembling a spider web.

　　2. Pathogenesis

　　1. Pathology

　　The lesions of colonic vascular ectasia often occur in the right half of the colon, especially the cecum. Literature reports that about 75% are distributed in the cecum and ascending colon, 12% in the transverse colon, 12% in the left half of the colon, and a few lesions can also occur in other parts of the digestive tract, including the stomach, duodenum, jejunum, and ileum. In patients with portal hypertension, the lesions are mostly scattered and multiple, and in other patients, the lesions are mostly solitary. In addition to portal hypertension, about 60% of patients may also have cardiovascular, pulmonary, and renal diseases, without skin or visceral hemangioma lesions. On ordinary formalin ethanol fixed specimens without special treatment, the typical pathological manifestations of colonic vascular ectasia are difficult to be found, especially in early lesions. Boley reported that in confirmed vascular lesions, the detection rate of routine pathological examination is only about 30%.

　　gross observation shows that in early and mild lesions, the mucosa is intact and there are no special manifestations; in patients with advanced stages, the mucosa at the lesion site can show a coral-like change, with the bulging varicose veins distributed radially and converging to a larger central penetrating vein; in patients with severe lesions, local mucosal erosion can be seen.

　　Histological examination shows that the diameter of the lesion is mostly between 0.1～1cm, the mucosa of the lesion site is intact, and there is no hyperplasia of cells and the sprouting of blood vessels in the lesion. The most common and obvious early abnormality is the明显扩张而迂曲的薄壁血管in the submucosa, the vast majority of which only have an endothelial cell layer, and occasionally a small amount of smooth muscle, which is structurally similar to dilated veins. In patients with advanced stages, vascular nodules composed of limited veins or dilated capillaries can be seen in the submucosa. In more extensive lesions, the number of dilated veins under the mucosa increases, deforms, and the blood vessels pass through the muscular layer of the mucosa and invade the mucosa. In severe cases, the mucosa can be replaced by tortuous and dilated vascular nodules.

　　There are two commonly used methods for the special treatment of specimens, one is to use barium gel injection; the other is to use silicone rubber injection. After the specimen is excised, the blood in the specimen vessels is cleaned with heparin saline, and any of the above substances is injected. After the injected material solidifies, the mucosal surface of the specimen can be observed, and tissue sections can be observed to see the cross-section of the tissue, which can easily see the dilated vascular丛.

　　2、发病机制

　　The pathogenesis of type I colonic angiectasia is related to postnatal factors causing obstruction of colonic venous return and submucosal arteriovenous shunts, including two causes: obstruction of submucosal venous return and portal venous return obstruction.

　　It is generally believed that the occurrence of type II and III colonic angiectasia is related to congenital developmental defects of the intestinal wall and vascular wall. Bolev believes that the occurrence of colonic angiectasia is related to the frequent and repeated increase in intracolonic pressure. The increase in intracolonic pressure or the contraction state of the intestinal wall smooth muscle compresses the vascular wall crossing the smooth muscle, obstructs the submucosal venous return, increases venous pressure. In addition, the inherent lesions and weaknesses of the venous wall lead to tortuous and dilated veins. At the same time, due to the venous dilation, the function of the precapillary sphincter is incomplete, leading to the formation of small arteriovenous fistulas, further increasing venous pressure and aggravating vascular dilation. According to the Laplace physical law: the pressure on the wall of a spherical cavity is proportional to the square of the radius of the sphere and the product of the pressure inside the cavity, that is, the pressure on the wall is proportional to the square of the radius of the sphere. The cecum and the proximal ascending colon are the largest parts of the entire colon in diameter. When a certain cause increases the intracolonic pressure, the pressure on the wall of the cecum and the proximal ascending colon is the greatest. This explains why colonic angiectasia is prone to occur in the proximal right colon.

　　Patients with massive bleeding in a short period may develop hemorrhagic shock; patients with chronic and recurrent small amounts of bleeding mainly develop iron deficiency anemia.

　　Massive blood loss causing shock is called hemorrhagic shock and is common in bleeding caused by trauma, peptic ulcer bleeding, esophageal variceal rupture, and bleeding caused by gynecological and obstetric diseases. Whether a patient develops shock after bleeding not only depends on the amount of bleeding but also on the speed of bleeding. Shock often occurs in cases of rapid and massive (more than 30-35% of total blood volume) bleeding without timely supplementation.

　　Colonic diverticulum varicose veins anemia iron deficiency anemia shock sclerosis

　　The majority of patients with colonic angiectasia have no clinical symptoms, only a few patients present with sudden, intermittent, or recurrent painless lower gastrointestinal bleeding as the clinical feature. Welch reported that among 72 patients with lower gastrointestinal bleeding, 43 were caused by colonic angiectasia, and Boley reported 32 cases of lower gastrointestinal bleeding caused by colonic angiectasia, including 23 cases with more than two episodes. Due to the differences in the amount of bleeding, bleeding rate, and lesion location, the clinical manifestations also show significant differences. Lesions located in the proximal colon, patients with more bleeding often have chestnut-like or tarry stools; lesions located in the left half of the colon, patients with more bleeding may have bright red stools; a few patients with massive bleeding in a short period may develop hemorrhagic shock due to acute massive bleeding; patients with chronic and recurrent small amounts of bleeding mainly manifest as chronic iron deficiency anemia.

　　In lower gastrointestinal bleeding caused by colonic angiectasia, most patients have a small amount of bleeding during each attack, which is self-limiting. More than 80% to 90% of the bleeding can stop spontaneously without special treatment, but it can recur frequently afterwards.

　　Nearly half of the lower gastrointestinal bleeding patients caused by colonic angiectasia have a history of coronary heart disease or aortic stenosis, and about 1/3 of the patients have colonic diverticulitis. On the one hand, this reflects that colonic angiectasia is a disease of the elderly, and on the other hand, it suggests that the occurrence of bleeding may be related to cardiovascular diseases, arterial hypertension, and local colonic inflammation around the expanded blood vessels.

　　For patients with recurrent lower gastrointestinal bleeding or a history of chronic iron deficiency anemia, after excluding common causes of gastrointestinal bleeding such as gastrointestinal tumors, esophageal varices, gastric mucosal bleeding, colonic diverticulitis, and colonic hemangioma through various examinations, it should be considered that there may be colonic angiectasia, especially for middle-aged and elderly patients over 60 years old and those with liver cirrhosis and portal hypertension.

　　Selective mesenteric angiography is an effective and accurate clinical diagnostic method, with an accuracy rate of 75% to 90%. However, due to the invasive nature of this examination, it poses certain risks to elderly patients. In addition, with the popularization and application of colonoscopy in recent years and the accumulation of experience, more clinical doctors tend to determine the diagnosis through colonoscopy. For lesions with active lower gastrointestinal bleeding, and bleeding speed above 0.1ml per minute, radionuclide scanning is also an effective examination method. Colonic barium double contrast examination can help exclude bleeding caused by colon tumors, colonic diverticulitis, and other factors.

　　The incidence of rebleeding after surgery for colonic vascular ectasia is about 4%, mainly due to the missed lesions, especially those located at the end of the ileum or other parts of the colon.

　　1. Develop good living habits, quit smoking and limit alcohol. Smoking, according to the World Health Organization's prediction, if people stop smoking, the world's cancer will decrease by 1/3 after 5 years; secondly, do not drink heavily. Cigarettes and alcohol are extremely acidic substances, and people who smoke and drink for a long time are prone to acidic体质.

　　2. Do not eat too much salty and spicy food, do not eat overheated, cold, expired, and deteriorated food; for the elderly, weak, or those with certain disease genetic genes, eat some cancer-preventive foods and alkaline foods with high alkalinity according to circumstances, and maintain a good mental state.

　　1. Routine blood test

　　There may be symptoms of iron deficiency anemia.

　　2. Blood biochemistry

　　The changes in indicators are related to the primary disease, such as abnormal lipid metabolism in patients with arteriosclerosis; abnormal blood glucose metabolism in patients with diabetes; abnormal plasma protein metabolism in patients with portal hypertension and liver disease in the late stage, and so on.

　　3. Liver and lung function

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

　　4. Double-contrast barium enema

　　Since the lesions of colonic angiectasis are localized submucosally and usually less than 1 cm in size, only about 15% of patients can see scattered small colonic mucosal erosion lesions or small ulcers during the double-contrast barium enema examination. Most patients do not show any abnormalities. The main purpose of double-contrast barium enema is to exclude other gastrointestinal lesions, such as colon tumors and diverticula.

　　5. Mesenteric angiography

　　The typical manifestation of colonic angiectasis during mesenteric angiography is the delayed venous emptying of contrast medium at the lesion site and the visible oval vascular clusters. The vascular clusters are most obvious in the arterial phase of angiography, mostly located at the terminal branches of the ileocolic artery, showing as oval clusters of vascular clusters. The contrast medium in the vessels is emptied slowly, and the venous phase still shows tortuous and dilated veins within the colonic wall, suggesting the presence of dilated venous plexuses submucosally. In cases with arteriovenous malformations or fistulae, due to the formation of arteriovenous shunts, venous engorgement can be seen early (within 4-5 seconds).

　　In patients with colonic angiectasis accompanied by acute bleeding, in addition to the above manifestations, contrast medium leakage into the intestinal lumen can also be observed at the lesion site, showing as persistent localized indistinct shadows around the vascular clusters.

　　6. Colonoscopy

　　In recent years, colonoscopy has been increasingly used in the diagnosis of colonic angiectasis. This method can not only confirm the results of mesenteric angiography and exclude bleeding caused by other causes, such as gastrointestinal tumors, but can also be used for biopsy and treatment of the lesions. Salem et al. compared the results of mesenteric angiography and colonoscopy in 56 patients with colonic angiectasis and found that 88% of the results were consistent. In addition, colonoscopy can often detect multiple small lesions that are difficult to find with mesenteric angiography. However, colonoscopy has high requirements for the cleanliness of bowel preparation and the experience level of the examiner.

　　The endoscopic manifestations of colonic angiectasis are closely related to the degree of the lesion. Since the usual lesions are located submucosally and the range of the lesions is small, in most mild cases, the mucosal manifestations are not obvious, and it is difficult to find obvious vascular lesions through endoscopy. When the dilated vessels invade the mucosal layer, typical flat or slightly raised red vascular spots can be seen at the lesion site, with a spider web-like or coral-like distribution of vascular networks within the spots. The local mucosa is congested and prone to bleeding. In patients with active bleeding, bleeding spots can be seen at the bleeding site during colonoscopy, with expanded vascular spots around them.

　　Although biopsy of the lesion can be performed through colonoscopy, there is a possibility of bleeding, so a cautious attitude should be maintained. In addition, it should be noted that the results of colonoscopy often show a high rate of false positives, and the interpretation of the results needs to be combined with the history of recent gastrointestinal bleeding and the results of mesenteric angiography.

　　7. 99mTc-labeled red blood cell scan

　　Compared with fiberoptic colonoscopy and mesenteric angiography, 99mTc-labeled red blood cell scanning has greater advantages in the diagnosis of colonic angiectasia bleeding. The examination is rapid, non-invasive, does not require any intestinal preparation, and has lower requirements for bleeding speed. The diagnosis of gastrointestinal bleeding by mesenteric angiography generally requires bleeding speed of more than 1-2ml per minute, while 99mTc-labeled red blood cell scanning only requires bleeding speed of more than 0.1ml per minute.

　　What kind of food is good for colonic angiectasia patients to eat:

　　Supplement protein and vitamins. The diet should choose easily digestible high-quality protein foods, as the digestive and absorption function is poor, easy to digest semi-liquid diet with less residue should be adopted, eat small and frequent meals to increase nutrition and improve symptoms.

　　First, treatment

　　Since most patients with colonic angiectasia are elderly, a considerable number of them have cardiovascular diseases, and most of the bleeding can stop spontaneously, therefore, for patients with less bleeding and confirmed by mesenteric angiography or fiberoptic colonoscopy, a more conservative treatment method can be initially adopted. However, it should be explained to the patients clearly that there is a possibility of recurrent bleeding.

　　1. Treatment by angiographic catheter

　　For lesions diagnosed by mesenteric angiography with active bleeding, local catheter placement and infusion of vasoconstrictors and hemostatic agents can be used for treatment. Vasopressin can be infused at a dose of 2U/min, and the medication should be continued for 12 hours. However, it should be noted that there is a possibility of intestinal ischemia, and the catheter may also displace. In addition, there is a possibility of recurrent bleeding after catheter removal. Athanasoulis and others reported that the efficacy of controlling bleeding with vasoconstrictor injection can reach 92%, but about 21% of patients experience recurrent bleeding. Although this method can be used repeatedly multiple times, it is more traumatic and poses certain risks to elderly patients. Absorbable gelatin sponge栓塞 through the mesenteric angiography catheter may cause intestinal infarction, with greater risk, and should not be used.

　　2. Treatment by fiberoptic colonoscopy

　　In recent years, hemostasis by fiberoptic colonoscopy has been increasingly adopted. Its advantages are safety, effectiveness, and the ability to be repeated. For small bleeding points, electrocoagulation can be used for hemostasis, that is, using a biopsy forceps to clamp the lesion, and applying low current (10-15W) for 1-3 seconds. For larger lesions, Nd-YAG laser hemostasis can be used. Hemostasis by fiberoptic colonoscopy can be both preventive and therapeutic. For patients with a history of lower gastrointestinal bleeding, and where fiberoptic colonoscopy suggests a previous bleeding site, preventive hemostasis can be performed. For areas where the effect of electrocoagulation is not certain, it can be performed multiple times. Attention should be paid to the appropriate depth of clamping during electrocoagulation to prevent perforation of the colon. In addition, it should be avoided to use mannitol for intestinal preparation before fiberoptic colonoscopy, as mannitol, after being metabolized in the intestines, can produce flammable gases, which are prone to cause intestinal cavity gas explosions during electrocoagulation. The effective rate of hemostasis by fiberoptic colonoscopy reported in literature is between 68% and 88%, and the incidence of recurrent bleeding is between 0% and 34%.

　　3. Surgical Treatment

　　Surgical treatment should be strictly controlled, and the choice of surgery should be limited to:

　　(1) Patients with recurrent lower gastrointestinal bleeding or chronic anemia, confirmed by mesenteric angiography to be caused by colonic vascular ectasia, with clear lesion site, non-surgical treatment is ineffective or recurrent rebleeding;

　　(2) Patients with a history of recurrent lower gastrointestinal bleeding or chronic iron deficiency anemia, but all examination results are normal, can exclude bleeding caused by tumors, diverticulitis, and so on. Angiography or colonoscopy shows limited colonic vascular ectasia, and highly suspects that this vascular ectasia is the source of bleeding. For such patients, the choice of surgery should be particularly cautious, and it is best to wait until the bleeding site is clearly identified before surgery;

　　(3) For patients with uncontrollable lower gastrointestinal bleeding, confirmed by angiography or colonoscopy to be caused by vascular ectasia, emergency surgery should be performed. The basic principle of surgery is to completely resect the diseased intestinal segment to prevent missed lesions, otherwise rebleeding may occur. The extent of surgery can be determined based on the range of lesions found by preoperative angiography and colonoscopy. During the operation, a comprehensive and careful examination of the mesenteric blood vessels should be conducted, and for segments with tortuous or dilated mesenteric blood vessels, the focus should be on checking for intramural vascular malformations or vascular ectasia clusters through the light transmission method.

　　In addition, all surgical patients should undergo adequate bowel preparation before surgery, and the lithotomy position should be adopted as much as possible during surgery. For patients suspected of having multiple lesions or where the lesion site is difficult to determine during surgery, intraoperative colonoscopy should be considered in hospitals with conditions. After the colon is inflated, the light from the colonoscope passing through the intestinal wall can be seen as a dense area of spider-like blood vessels at the lesion site. This method is simple and easy to perform, and can effectively improve the success rate of surgery.

　　II. Prognosis

　　The incidence of rebleeding after surgery for colonic vascular ectasia is about 4%, mainly due to the missed lesions, especially those located at the end of the ileum or other parts of the colon.