The hepatoduodenal ligament is a double-layered tubular role of peritoneum that constitutes part of the lesser omentum. It stretches between the porta hepatis of the liver and the proximal portion of the duodenum. Its main function is to encompass and accompany the portal triad which are three structures running in close proximity, including the hepatic artery proper, the hepatic portal vein and the common bile duct.
The hepatic artery proper is a large branch of the common hepatic artery, making up the first of the three structures in the portal triad. Its first branch is the small supraduodenal artery that supplies the duodenal bulb, before the vessel continues on and branches again into the right gastric artery that can be found running along the lesser gastric curvature. It anastomoses with the left gastric artery that branches directly from the celiac trunk. At this point, the artery finally bifurcates into the right and left hepatic arteries, however there are some common anatomical variations of this part of the vessel. The superior mesenteric artery may replace the right hepatic artery and the left gastric artery may replace the left hepatic artery. If the right hepatic artery is present, it will give a terminal branch known as the cystic artery.
The hepatic portal vein, the second structure of the triad, is a large blood vessel that collects the deoxygenated blood from the spleen and the gastrointestinal tract and returns it to the liver. Once inside the liver, the nutrients contained within the blood after their absorption from the intestines are processed and any toxins present are filtered. As much as 75% of the blood the liver receives comes directly from the hepatic portal vein, with the remaining 25% flowing in from the hepatic artery proper. The hepatic veins are responsible for passing the filtered blood on to the inferior vena cava and back to the heart. This vein if formed by the convergence of the superior and inferior mesenteric veins, the splenic veins, the gastric veins and the cystic veins.
The common bile duct is the third and final structure in the portal triad. It is a tube like anatomical structure formed by the convergence of the common hepatic duct and the cystic duct of the gallbladder. The pancreatic duct also merges with it as it nears the pancreas and the point where the two ducts join is known as the ampulla of vater and is surrounded by a muscular sphincter known as the sphincter of oddi, which controls the release of bile from the gallbladder as it opens and closes. The common bile duct drains into the proximal portion of the duodenum and is stimulated by the hormone cholecystokinin which is secreted due to the ingestion of a fatty meal.
Portal hypertension is a serious disorder that affects the hepatic portal vein. An increase in the blood pressure is usually secondary to liver cirrhosis. The most common clinical signs of portal hypertension include ascites, spider nevi, esophageal varices, caput medusae and palmar erythema.
Choledocholithiasis is a disorder of the common bile duct in which it becomes partially or completely blocked. Gallstones are usually the culprits and if left untreated, they leave the gallbladder at greater risk of infection.