Epidemiologic data Hemangiomas and vascular malformations are usually found on the skin of the body and extremities, while hemangiomas and vascular malformations of the gastrointestinal tract are rare and were first reported in 1839 by the British physician Philips. These lesions can occur anywhere in the GI tract; the small intestine is a common site for GI hemangiomas and vascular malformations, and about 10% of occupying lesions in the small intestine have been confirmed to be hemangiomas and vascular malformations. The incidence of colorectal hemangioma and vascular malformation may be slightly lower than that of small intestine. From the 1930s to the mid-1970s, only 200 cases were reported in foreign literature, and there are not many credible reports in China, among which the Department of Anorectal Surgery of Shanghai Changhai Hospital reported that 6 cases were admitted and treated surgically from 1994 to 2005. The literature shows that colonic and rectal lesions account for 38% of such lesions, and about half of the colorectal lesions are found in the sigmoid and rectum; of course, this may also be due to a biased sample because of the higher consultation rate due to the more obvious symptoms of sigmoid and rectal lesions. The majority of GI hemangiomas and vascular malformations are congenital and non-genetic, often with lesions present at birth. Patients are often misdiagnosed and treatment is delayed. Studies have shown that such patients are diagnosed as early as 2 months after birth and are correctly diagnosed as late as 79 years of age, with a mean age at diagnosis of 16 years; in the group of patients with bleeding as the primary symptom, the mean age at diagnosis is 5 years, suggesting that bleeding symptoms contribute to early diagnosis. Overall, these diseases tend to occur in younger age groups, with a male to female prevalence ratio of approximately 1:2.5, with a higher prevalence in women, while the male to female prevalence ratio for colorectal hemangiomas and vascular malformations is close to 1:1, which is roughly equivalent. Histopathology and classification As the name implies, there are two categories of GI hemangiomas and vascular malformations, namely hemangiomas and vascular malformations. In fact, the term “hemangioma” is widely used in clinical practice, but it is often misused, especially with specific modifications such as “strawberry hemangioma”, “cavernous hemangioma”, and “cavernous hemangioma”. The term “hemangioma” is widely used in clinical practice, but is often misused, especially when it is modified with specific terms such as “strawberry hemangioma”, “cavernous hemangioma”, and “capillary hemangioma”. In 1982, Mulliken and Glowacki established a strict classification of hemangiomas and vascular malformations based on histologic morphology and the rate of endothelial cell renewal, and this classification has been used ever since. According to the Mulliken and Glowacki classification, the characteristics that must be present in a hemangioma are an abnormally high proliferation of vascular endothelial cells; in this sense, infantile hemangiomas, rapid self-limiting congenital hemangiomas, non-rapid self-limiting congenital hemangiomas, Kaposi-type hemangioendotheliomas, and plexiform hemangiomas are all hemangiomas. All of these lesions develop at birth and most of them regress spontaneously. Glucocorticoids and interferons can accelerate this regression process and thus be used to treat these lesions. Vascular malformations are not characterized by a high degree of endothelial proliferation, and their endothelium renews at the same rate as normal endothelial cells. Vascular malformations are classified as arteriovenous malformations, venous malformations, lymphatic vascular malformations, lymphatic-venous malformations, and capillary malformations according to the site of the malformation. In 1996, the International Society for the Study of Vascular Anomalies adopted this classification. Common Vascular Malformations Although hemangiomas can occur in the gastrointestinal tract, in fact, vascular malformations of the gastrointestinal tract are more common clinically, especially the common “cavernous hemangioma” which should in fact be referred to as a “cavernous vascular malformation”. Vascular malformations originate from embryonic abnormalities at the morphogenetic stage, resulting in a lack of vascular smooth muscle in the endothelium, which causes the blood vessels to swell under the hydrostatic pressure of the blood flow, thus forming a vascular malformation, a process in which there is no vascular neovascularization, which is the essential feature that distinguishes it from a flow tubular tumor. Capillary malformations often develop in the skin of the anal canal or perianal skin, in the small intestine, and in the appendix, and are often solitary, lacking well-defined lesion margins; about half of capillary malformations are associated with mucosal ulcers and are accompanied by inflammatory edema of the ulcerated surface. The pathology of capillary malformations is characterized by dilated thin-walled capillaries with a single layer of smooth muscle in the vessel wall. Approximately 80% of rectosigmoid vascular malformations have been reported to be cavernous vascular malformations, which differ from capillary malformations in that the vessel wall may consist of one or more layers of vascular endothelium. Focal cavernous vascular malformations can manifest in the form of polyps, which can cause obstruction, abdominal pain, diarrhea, and other corresponding symptoms in addition to bleeding, while multiple cavernous vascular malformations, which can involve the digestive tract up to 750 px, have a multifocal onset. Spongiform vascular malformations may exhibit circumferential growth with a potential risk of local invasion of adjacent tissues; rectal invasion occurs in 70% of cases. Most vascular malformations present as intraluminal lesions, but in a few cases of cavernous vascular malformations, the vascular malformation breaks through the submucosa and invades further and thus invades adjacent structures, forming multifocal clusters of lesions from a single focal lesion. Some GI vascular malformations co-exist with vascular malformations of the skin, brain, and spinal cord and specific clinical manifestations such as limb and bone hypertrophy, varicose veins, and arteriovenous fistulas, constituting specific syndromes such as Blue rubber bleb nevus syndrome, klippel-Trenaunay-Weber syndrome, etc. Although gastrointestinal vascular malformations are often associated with cutaneous vascular malformations, only 1.8% of cutaneous vascular malformations are associated with gastrointestinal vascular malformations. Pathophysiology According to Mulliken and Glowacki classification, the essential difference between hemangiomas and vascular malformations is the presence or absence of vascular smooth muscle hyperplasia. This abnormality occurs mainly during the morphogenetic stage of the embryo and is associated with intrinsic defects in the endothelium and the secretion of growth factors. Because of the 1:2.5 ratio of male to female incidence of GI hemangiomas and vascular malformations, it has been suggested that this abnormal lesion may be related to hormonal abnormalities. Vascular abnormalities occur at different stages in different lesion types, such as cavernous vascular malformations, which occur during stem cell division, and capillary malformations, which occur at an earlier stage of embryonic formation. In Kasabach-Merritt syndrome (a syndrome associated with gastrointestinal vascular malformations), the depletion of fibrinogen, coagulation factors V and VIII often results in severe coagulation abnormalities similar to DIC, leading to uncontrolled hemorrhage with a mortality rate of 35%. . Prolonged hemodynamic abnormalities often result in localized calcification of the vessel wall and the formation of venoliths, which are seen in more than 50% of cases. Vascular malformations of the GI tract are often associated with anemia, with intraluminal hemorrhage due to vascular erosion and rupture of the malformed vessels being the main cause of anemia, and the massive destruction of reticulocytes due to thrombosis within the malformed vessels also exacerbating the anemic state. This abnormal coagulation state and thrombosis often lead to focal or segmental ischemia of the diseased intestinal canal. Cases of invasion of the surrounding organs by malformed vessels have been reported in the literature, with sigmoid vascular malformations being the most common and the organs invaded being mainly the sacrum, bladder and uterus; despite the invasive capacity of the vascular malformation, few cases with associated malignancy have been reported. The patient’s history is often accompanied by a history of previous misdiagnosis, with more than 80% of such patients having undergone incorrect surgical treatment, including hemorrhoidectomy, prior to diagnosis. According to previous studies, most cases of gastrointestinal hemangiomas and vascular malformations, especially colorectal lesions, are often misdiagnosed as mixed hemorrhoids, internal hemorrhoids, ulcerative colitis, colonic polyps, and tumors. About 80% of the cases show symptoms, mainly painless bleeding from the intestinal cavity, while nearly half of the cases are associated with the corresponding manifestations of hemorrhagic anemia, including pallor, growth retardation, dizziness, etc. Initial bleeding is often seen in early childhood, with a gradual increase in the frequency and volume of bleeding later. The bleeding is predominantly intraluminal, with a small number of cases of transmural or plasma muscle vascular malformations that may be associated with intraperitoneal and retroperitoneal bleeding. Studies have shown that lesions located in the distal intestine and larger lesions can lead to more severe bleeding. Intestinal hemangiomas and vascular malformations can also cause intestinal obstruction, although their development is uncommon. Polypoid hemangiomas and vascular malformations can lead to intussusception, and vascular malformations surrounding the intestinal wall can lead to intestinal lumen obstruction. Patients with low rectal mucosa and anal canal skin vascular malformations may complain of constipation and urgency. Abdominal and pelvic pain is also a common symptom. Physical examination Gastrointestinal hemangiomas and vascular malformations often lack specific positive signs and findings on physical examination. If the lesion is located in the distal intestine, it can be detected during anal finger examination. These lesions are often not easily recognized on palpation and are soft, compressible, and have a granular surface. When the lesion is large, it can sometimes be palpated as a nodule on abdominal palpation. The results of blood analysis often suggest acute or chronic anemia caused by chronic or acute blood loss. In cases with larger lesions and more bleeding, there is often a decrease in coagulation factors such as fibrinogen, platelets, coagulation factors V and VIII, which are demonstrated in the corresponding blood tests. Imaging abdominal plain films Blood segregation and turbulence at the site of the lesion often leads to calcium salt deposits forming phleboliths, which are seen in more than 50% of cases of gastrointestinal hemangiomas and vascular malformations. Therefore, abdominal plain radiographs showing phleboliths, when they are located in the intestinal wall, multiple and do not extend into the soft tissues, especially when they are located lateral to the trunk and away from the pelvic plexus, often suggest the presence of intestinal hemangiomas and vascular malformations. Venoliths are uncommon in the normal population, with a detection rate of less than 5% in the normal population aged less than 30 years; this suggests that the presence of venoliths has a good specificity and sensitivity for guiding the diagnosis of intestinal angiomas and vascular malformations. Intestinal angiography Angiography can suggest intestinal obstruction or polyp-like lesions due to angiomas and vascular malformations, and anterior rectal displacement and widening of the presacral space can suggest the presence of giant spongy vascular malformations of the rectum. However, polypoid angiomas and vascular malformations may rupture during the inflation phase of air-barium double imaging. Computed tomography With CT, thickening of the intestinal wall with or without phleboliths is often found in cases of intestinal hemangiomas and vascular malformations. The extent of extra-mucosal extension of the vascular lesion and the invasion of surrounding tissues can be assessed by CT scan. Magnetic resonance imaging MRI is also useful for diagnosis, especially for rectal vascular malformations. Colorectal hemangiomas and vascular malformations often appear as areas of high signal on T-2 weighted MRI images, due to lower blood flow velocities. High-signal areas are also seen in the perirectal fatty tissue of rectal hemangiomas, which contain waveform signal shadows within the high-signal areas because of the small vessels in this fatty tissue supplying the hemangioma. The above characteristic MRI imaging findings are highly specific and are not seen in other diseases. This also suggests why MRI has a greater role than CT in the diagnosis of colorectal vascular malformations and hemangiomas. Although hemorrhoids appear similar to hemangiomas and vascular malformations on MRI images, lesion site and perirectal fat high signal and waveform signal shadowing can distinguish between the two. Calcifications and vein stones do not show up significantly in MRI. Ultrasonography Ultrasonography plays an important role in the diagnosis of colorectal vascular malformations and hemangiomas because of its non-radiation, easy operation and its ability to discriminate soft tissue structures. In particular, the application of ultrasound Doppler technique can suggest the course of blood flow in the diseased vessels. Angiography Used to be the main diagnostic modality for intestinal vascular tumors and vascular malformations. Mesenteric angiography often reveals characteristic areas of contrast accumulation in the intestinal wall, often in the sigmoid colon and rectum, and the presence of such areas of contrast accumulation suggests a temporary absence of active bleeding. Angiography is useful in detecting multiple coexisting lesions. Delayed visualization in the venous phase is a common type of lesion. However, the diagnostic significance of angiography for hemangiomas and vascular malformations may be reduced if thrombosis is present, when the lesion is hyperaemic or avascular. Endoscopy Colonoscopy is critical in the diagnosis of hemangiomas and vascular malformations. As mentioned in relation to dual gas-barium imaging, the inflation phase of the colon may cause rupture of polypoid hemangiomas and vascular malformations. Endoscopically, submucosal lesions are seen as blue and red variable nodules. Endoscopy may reveal pinpoint bleeding spots in the lesion area, mucosal ulcers in the lesion area, mucosal edema, nodular lesions, and vascular congestion, and these nonspecific endoscopic manifestations may lead to misdiagnosis of inflammatory bowel disease and internal hemorrhoids. Biopsy is not usually recommended during endoscopy to avoid inducing bleeding, except in cases requiring a definitive pathologic diagnosis. Treatment Pharmacologic treatment As with other etiologies of GI bleeding, the primary goal of emergency treatment is to maintain hemodynamic stability. The application of glucocorticoids has proven to be effective in cases of pathologically confirmed hemangiomas. However, most common clinical GI vascular lesions are vascular malformations, so pharmacological treatment is usually ineffective. Endoscopic treatment Ideal narrow-base polypoid vascular lesions can be treated with endoscopic ligature resection and incisional cautery, which are usually ideal. Endoscopic argon knife treatment has been reported to be more effective in severe cases of blood in the stool. For rectosigmoid vascular malformations, some studies have reported good results of endoscopic sclerotherapy, and some studies have reported one case of recurrence of hemorrhage in stool and death after 4 months after good short-term hemostasis by sclerotherapy injection. According to the current international consensus, endoscopic treatment techniques should only be used in cases that are not suitable for surgical treatment. Surgery With the exception of some conservative views, most surgeons agree that surgery is the mainstay of treatment for intestinal vascular malformations and hemangiomas. Prior to the 1970s, the recommended treatment option for rectosigmoid vascular malformations was combined abdominal perineal and distal colorectal resection. After anus-preserving surgery became the prevailing concept, low anterior rectal resection and mucosal resection are the current standard of care. Other procedures include segmental resection of the colon, low anterior rectal resection without mucosal resection, and modified Parks-transanal rectal resection with colonic and anal canal prolapse anastomosis. During the surgical operation, the distal margin of the resected portion of the diseased colon can be clearly localized by identifying structures such as subplasmic tortuous diseased vessels, stiff diseased bowel segments, and thickened mesentery of the diseased segment. During mucosal resection, a sleeve is placed in the plane between the mucosal layer and the muscular layer. The 12.5 px of mucosa proximal to the dentate line is excised. Some physicians advocate separating the resection to the level of the levator muscle, preserving 3-100 px of the anal canal or the distal bowel and performing a manual anastomosis with a routine ileostomy. For more proximal colonic lesions, segmental resection or full wedge resection of the intestinal canal is feasible. Conclusion Given the relative rarity and frequent misdiagnosis in clinical practice, the possibility of gastrointestinal vascular malformations and hemangiomas needs to be considered in the management of cases of gastrointestinal bleeding, especially in young people with recurrent painless bleeding episodes. It is reassuring to know that the diagnosis of gastrointestinal hemangiomas and vascular malformations can be based on clues at multiple levels, including historical features, clinical manifestations, and imaging examinations. As for the treatment, transabdominal colectomy remains the currently recommended standard of care.