Veins are blood vessels in the circulatory system of humans and most other animals that carry blood toward the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are those of the pulmonary and fetal circulations which carry oxygenated blood to the heart. In the systemic circulation arteries carry oxygenated blood away from the heart, and veins return deoxygenated blood to the heart, in the deep veins.
The portal vein or hepatic portal vein (HPV) is a blood vessel that carries blood from the gastrointestinal tract, gallbladder, pancreas and spleen to the liver. This blood contains nutrients and toxins extracted from digested contents. Approximately 75% of total liver blood flow is through the portal vein, with the remainder coming from the hepatic artery proper. The blood leaves the liver to the heart in the hepatic veins.
An anastomosis is a connection or opening between two things that are normally diverging or branching, such as between blood vessels, leaf veins, or streams. Such a connection may be normal or abnormal ; it may be acquired or innate ; and it may be natural or artificial. The reestablishment of an anastomosis that had become blocked is called a reanastomosis. Anastomoses that are abnormal, whether congenital or acquired, are often called fistulas.
Budd–Chiari syndrome is a very rare condition, affecting one in a million adults. The condition is caused by occlusion of the hepatic veins that drain the liver. The symptoms are non-specific and vary widely, but it may present with the classical triad of abdominal pain, ascites, and liver enlargement. It is usually seen in younger adults, with the median age at diagnosis between the ages of 35 and 40, and it has a similar incidence in males and females. The syndrome can be fulminant, acute, chronic, or asymptomatic. Subacute presentation is the most common form.
Esophageal varices are extremely dilated sub-mucosal veins in the lower third of the esophagus. They are most often a consequence of portal hypertension, commonly due to cirrhosis. People with esophageal varices have a strong tendency to develop severe bleeding which left untreated can be fatal. Esophageal varices are typically diagnosed through an esophagogastroduodenoscopy.
Portal hypertension is abnormally increased portal venous pressure – blood pressure in the portal vein and its branches, that drain from most of the intestine to the liver. Portal hypertension is defined as a hepatic venous pressure gradient greater than 5 mmHg. Cirrhosis is the most common cause of portal hypertension; other, less frequent causes are therefore grouped as non-cirrhotic portal hypertension. When it becomes severe enough to cause symptoms or complications, treatment may be given to decrease portal hypertension itself or to manage its complications.
Transjugular intrahepatic portosystemic shunt is an artificial channel within the liver that establishes communication between the inflow portal vein and the outflow hepatic vein. It is used to treat portal hypertension which frequently leads to intestinal bleeding, life-threatening esophageal bleeding and the buildup of fluid within the abdomen (ascites).
Portal vein thrombosis (PVT) is a vascular disease of the liver that occurs when a blood clot occurs in the hepatic portal vein, which can lead to increased pressure in the portal vein system and reduced blood supply to the liver. The mortality rate is approximately 1 in 10.
A portosystemic shunt or portasystemic shunt, also known as a liver shunt, is a bypass of the liver by the body's circulatory system. It can be either a congenital or acquired condition and occurs in humans as well as in other species of animals. Congenital PSS are extremely rare in humans but are relatively common in dogs. Improvements in imaging and awareness have contributed to an increase in cases.Thus a large part of medical and scientific literature on the subject is grounded in veterinary medicine.
In human anatomy, the hepatic portal system or portal venous system is the system of veins comprising the portal vein and its tributaries. The other portal venous systems in the body are the renal portal system, and the hypophyseal portal system.
The rectal venous plexus is the venous plexus surrounding the rectum. It consists of an internal and an external rectal plexus. It is drained by the superior, middle, and inferior rectal veins. It forms a portosystemic (portocaval) anastomosis. This allows rectally administered medications to bypassing first pass metabolism.
Collateral circulation is the alternate circulation around a blocked artery or vein via another path, such as nearby minor vessels. It may occur via preexisting vascular redundancy, as in the circle of Willis in the brain, or it may occur via new branches formed between adjacent blood vessels (neovascularization), as in the eye after a retinal embolism or in the brain when an instance of arterial constriction occurs due to Moyamoya disease. Its formation may be related by pathological conditions such as high vascular resistance or ischaemia. It is occasionally also known as accessory circulation, auxiliary circulation, or secondary circulation. It has surgically created analogues in which shunts or anastomoses are constructed to bypass circulatory problems.
A circulatory anastomosis is a connection between two blood vessels, such as between arteries, between veins or between an artery and a vein. Anastomoses between arteries and between veins result in a multitude of arteries and veins, respectively, serving the same volume of tissue. Such anastomoses occur normally in the body in the circulatory system, serving as back-up routes in a collateral circulation that allow blood to flow if one link is blocked or otherwise compromised, but may also occur pathologically.
The thoracoepigastric vein runs along the lateral aspect of the trunk between the superficial epigastric vein below and the lateral thoracic vein above and establishes an important communication between the femoral vein and axillary vein. This is an especially important vein when the inferior vena cava (IVC) becomes obstructed, by providing a means of collateral venous return. It creates a cavocaval anastomosis by connecting with superficial epigastric veins arising from femoral vein just below inguinal ligament.
In the course of the round ligament of the liver, small paraumbilical veins are found which establish an anastomosis between the veins of the anterior abdominal wall and the portal vein, hypogastric, and iliac veins. These veins include Burrow's veins, and the veins of Sappey – superior veins of Sappey and the inferior veins of Sappey.
The left gastric vein is a vein that derives from tributaries draining the lesser curvature of the stomach.
The esophageal veins drain blood from the esophagus to the azygos vein, in the thorax, and to the inferior thyroid vein in the neck. It also drains, although with less significance, to the hemiazygos vein, posterior intercostal vein and bronchial veins.
A portacaval shunt, portocaval shunt, or portal-caval shunt is a treatment for portal hypertension. A connection is made between the portal vein, which supplies 75% of the liver's blood, and the inferior vena cava, the vein that drains blood from the lower two-thirds of the body. The most common causes of liver disease resulting in portal hypertension are Budd–Chiari syndrome or cirrhosis. Budd–Chiari syndrome should not be mistaken for cirrhosis.
Anorectal varices are the dilation of collateral submucosal vessels due to backflow in the veins of the rectum. Typically this occurs due to portal hypertension which shunts venous blood from the portal system through the portosystemic anastomosis present at this site into the systemic venous system. This can also occur in the esophagus, causing esophageal varices, and at the level of the umbilicus, causing caput medusae. Between 44% and 78% of patients with portal hypertension get anorectal varices.
The Sugiura procedure is a surgical technique that involves the removal and transection of the blood vessels that supply the upper portion of the stomach and the esophagus. The procedure also involves a splenectomy. The operation was originally developed to treat bleeding esophageal varices that were untreatable by other conventional methods. It was originally developed as a two-step operation, but has been modified numerous times by many surgeons since its original creation.
