Anastomoses are connections between anatomical structures, such as those found between blood vessels, nerves, lymphatic vessels, and hollow organs, and ensure the formation of a bypass circuit when one of the connecting links is impaired. In surgery, the physician creates anastomoses artificially in some cases, and a distinction is made between end-to-end, side-to-side and end-to-side anastomoses according to the particular form of this surgical procedure. One of the most common complaints associated with anastomoses is portal vein congestion, which can cause the anastomoses in this area to have more blood flow than usual, leading to the formation of varicose veins in the esophagus or around the belly button.
What is anastomosis?
Anastomosis is the medical term for a connection between anatomical structures. Such connections occur especially between hollow organs, blood and lymph vessels, but also play a role for nerves. Blood vessels, for example, form anastomoses only with other blood vessels, and lymph vessels connect exclusively with nerves. Surgery also sometimes refers to artificially created connections as anastomoses, for example the surgically restored continuity of the gastrointestinal tract after resections of individual sections of the stomach or intestine. However, surgical restoration of nerve connections is also associated with the artificial creation of anastomoses. As a rule, natural anastomoses are distinguished by organ. Surgical anastomoses, on the other hand, are distinguished by the physician according to their form. Differentiation by organ results in subgroups such as vascular anastomoses, intestinal anastomoses, or ureteral anastomoses. Differentiation by shape gives rise to groups such as end-to-end anastomosis, end-to-side anastomosis, or side-to-side anastomosis.
Anatomy and structure
The anatomy of an anastomosis depends largely on its functions and thus differs according to the particular organ or depending on the anatomical structures that it connects. In the lymphatic system, for example, anastomoses connect lymphatic vessels at the same level. In contrast, an example of an anastomosis between blood vessels is the corona mortis, which is naturally abnormally strong and connects the inferior epigastric artery with the obturator artery. Again, the riolan anastomosis has a different structure. This inconstant vascular connection is located in the colon between the media colic artery, the superior mesenteric artery, and the sinistra colic artery. It has an even more complex structure than the corona mortis and plays a role primarily in arterial occlusions of the colon. In connection with nervous anastomoses, the anterior region of the mandible should be mentioned above all, where the nerves of each side of the jaw are connected. Artificial anastomoses can take either end-to-end, side-to-side or end-to-side form, which means their anatomy differs even more. For example, in end-to-end anastomoses, the surgeon connects two sections of a hollow organ at their open ends. In end-to-side connections, he instead sutures one hollow organ section to another section that he has opened laterally. In a side-to-side artificial anastomosis, again, two sections of a hollow organ are opened laterally to be sutured together.
Function and tasks
One of the most important functions of anastomoses is to form bypasses. This is especially true for anastomoses between vascular structures, such as the Riolan anastomosis. This connection ensures blood flow to the intestine in the event of an arterial occlusion in the colon by diverting blood flow from the occluded artery to another artery. In this way, anastomoses between arterial structures regulate blood flow and, more importantly, prevent necrosis, which would cause tissue death if blood flow were inadequate. Anastomoses between nerves also form bypass circuits under certain circumstances. In this way, they safeguard the transmission of stimuli and thus the functional processes in the nervous system. An example of such an anastomosis is the Jacobson anastomosis. In the lymphatic system, anastomoses also serve the purpose of detour. If the lymph flow in one plane is interrupted by vessels, for example, the anastomoses divert the lymph to an adjacent lymphatic vessel. In this way, the connections prevent lymphedema in the event of a flow interruption.
Diseases
High disease value may be associated with arterial anastomoses in particular. This is especially true in cases of arteriovenous malformations, which are congenital malformations of blood vessels. In the context of such malformations, arteries are sometimes directly connected to veins, which can have many threatening consequences. Frequently, in connection with pathological anastomoses, congestion of the portal vein also occurs, in the course of which the portocaval anastomoses are supplied with more blood than usual. This can lead to varicose veins in the esophagus, which are particularly risky. Less commonly, this condition also results in the formation of varicose veins in the area of the belly button. In addition, a relatively common condition is atypical anastomoses in the vessels of the placenta. This phenomenon is sometimes the cause of fetofetal transfusion syndrome, which may affect identical twins. In the case of multiple twins, hormones may be exchanged between the fetuses due to atypical anastomoses in the placenta. If the two fetuses are of different sexes, the hormonal exchange can possibly affect the development of the reproductive organs on the female fetus. Although apart from those mentioned, many other complaints can be associated with anastomoses, such as fecal incontinence in the case of ileum-pouch-anal anastomosis. Except for those mentioned, however, virtually all other anastomotic disorders tend to be rarities and therefore will not be presented in detail.