Introduction

The hepatoduodenal ligament is a thick anatomical structure wrapped in the peritoneum that constitutes part of the lesser omentum. The hepatoduodenal ligament runs from the porta hepatis to the proximal 2 cm of the duodenum. The hepatic artery proper, common bile duct, and portal vein run through the ligament near its free edge to reach the liver. These three structures are often referred to as the portal triad.[1] The hepatic artery proper is a branch of the common hepatic artery, originating from the celiac trunk. The hepatic portal vein is the main drainage site of the spleen and the small and large intestines. It brings in nutrient-rich but oxygen-poor blood from these organs via the splenic vein, superior mesenteric vein, and inferior mesenteric vein. The common bile duct is a tube-like structure that helps carry bile from the gallbladder to the lumen of the duodenum. It forms from the unification of the cystic duct from the gallbladder and the common hepatic duct. These three important structures exist within the hepatoduodenal ligament. Understanding the location, content, and function of the hepatoduodenal ligament is important when pathology arises or performing surgery in surrounding structures.[2][1][3][4] See image. Abdominal Cavity Organs.

Structure and Function

The hepatoduodenal ligament is a double-layered tubular structure composed of peritoneum that encloses the portal triad. The opening behind the free edge of the hepatoduodenal ligament is the omental foramen (foramen of Winslow), the only opening of the lesser sac, and the sole connection between the lesser sac and the greater peritoneal cavity.[5] To locate the hepatoduodenal ligament, one may start from the hepatogastric ligament and follow the lesser curvature of the stomach inferiorly towards the pylorus. The hepatoduodenal ligament will be felt or seen connected to the proximal portion of the duodenum. The primary function of this ligament is to protect and encompass the three important structures known as the portal triad, which provides adequate blood supply to the liver and promotes bile flow into the lumen of the duodenum. About 75% of the liver's blood supply comes from the portal vein, and the remaining 25% comes from the hepatic artery.[6] The hepatoduodenal ligament can also serve as a landmark during certain surgical procedures such as the Pringle maneuver.[4]

Embryology

During the embryological formation of the gastrointestinal tract, the foregut is suspended from the abdominal wall by a double layer of peritoneum called the mesentery. The hepatoduodenal ligament derives from the ventral mesentery between the liver and the stomach as part of the lesser omentum. After the stomach migrates to its final location, the space posterior to it becomes the lesser sac, and the opening to this sac appears at the distal edge of the hepatoduodenal ligament. This opening is called the foramen of Winslow.[5]

Blood Supply and Lymphatics

Various vessels surround the hepatoduodenal ligament that may contribute to the blood supply of this ligament. Aside from the hepatic artery proper and the portal vein that runs through the ligament, other vessels are adjacent to this structure. The right gastric artery, which derives from the left hepatic artery, the common hepatic artery, and part of the gastroduodenal artery seems to be associated with the blood supply of the hepatoduodenal ligament, and blood is typically drained by the right gastric vein.[7] The hepatoduodenal ligament has lymphatic pathways, which will flow into the Pecquet cistern at a sub-diaphragmatic level. It also has the name "pars tensa" of the small omentum; its thickness contains the portal triad, that is, the portal vein, the hepatic artery, and the common bile duct.

Nerves

The nerve supply of the hepatoduodenal ligament remains undetermined, but postsynaptic sympathetic nerve fibers may be associated with the vascular structure. The vagus nerve divides into both anterior and posterior branches as it enters the abdominal region. The anterior branch further divides into smaller branches, which travels through the lesser omentum. The vagus nerve also runs through the portal triad, and it may play a role in the parasympathetic nerve supply of the ligament.[8]

Muscles

No clinically significant skeletal or smooth muscle fibers have associations with the hepatoduodenal ligament. 

Physiologic Variants

Although anatomic variations of the hepatoduodenal ligament are rare, the content of the ligament may differ in the general population. Variation of the hepatic artery is common and is clinically important to identify before any surgery in this region is performed. If a specific significant variation exists, devastating hemorrhagic complications may occur. The most common variants include the right hepatic artery arising from the superior mesenteric artery that runs behind the pancreatic head along the right posterolateral flank of the portal vein, and the left hepatic artery as it arises from the left gastric artery that runs in the lesser omentum.[9]

Surgical Considerations

When the liver is injured during surgery or penetrating trauma, the bleeding can be torrential and quickly lead to hemorrhagic shock or death. A lifesaving maneuver sometimes performed to stop the bleeding is the Pringle maneuver, which was first described in 1908 by a surgeon named James Hogarth Pringle in Glasgow, Scotland. This surgical maneuver involves compressing the hepatoduodenal ligament with a clamp. This clamping interrupts blood flow to the liver and helps control bleeding. If no clamp is available, one may use their fingers to compress the ligament. If the bleeding from the liver continues, this indicates that the inferior vena cava or the hepatic vein may have suffered an injury.[2]

Complications of the Pringle maneuver include ischemia and portal hypertension. It may also lead to a reperfusion phenomenon if the clamping time is prolonged. There are no absolute contraindications to the Pringle maneuver. However, in patients with a compromised liver function such as cirrhosis, one should not clamp for more than 10 minutes at a time.[10] Otherwise, it can lead to permanent injury to the liver. The clamp should be intermittently released at 30 to 45 minutes so that the liver is not completely without blood for an extended period to minimize complications.[2]

Clinical Significance

Viscera of the upper abdomen, pelvis, retroperitoneum, and body wall all connect via many peritoneal ligaments, including the hepatoduodenal ligament. As a result of this proximity, the hepatoduodenal ligament is an important pathway of inflammatory and neoplastic disease between the stomach, retroperitoneum, and the porta hepatis through mechanisms such as direct invasion and lymphatic extension. Lymph nodes that surround this ligament can facilitate the spread of disease.[11] For example, cancer from the pancreas and colon can spread to the nodes surrounding the superior mesenteric artery and eventually travel up the lymphatic channels in the hepatoduodenal ligament to the liver. Lymphatic fluid can also travel from the liver and biliary system to lymph nodes adjacent to the duodenum and pancreas, promoting the spread of disease to the retroperitoneum. Direct invasion can occur with certain inflammatory diseases such as pancreatitis and inflammation from the biliary system. A disease that originates from the lesser curvature of the stomach, such as gastric cancer, can also spread to lymph nodes via direct invasion.[12] The hematologic spread of disease can occur through the portal vein and carry disease from the gastrointestinal tract to the liver.[11] On rare occasions, vascular complications may occur when disease travels through the hepatoduodenal ligament, such as in hepatic arterial pseudoaneurysms and portal vein thrombosis.[13][4][14]

Other Issues

The tools for assessing the hepatoduodenal ligament are different:

• Ultrasonography (US) is the simplest and most informative tool about blood flow.
• Multidetector computed tomography (MDCT) can provide a general evaluation.
• Magnetic resonance imaging (MRI) has a higher resolution for soft tissues.
• Magnetic resonance (MR) cholangiography is useful to understand the clinical situation of the biliary tract.
• Endoscopic retrograde cholangiopancreatography (ERCP) is used for an initial and general evaluation.
• Fludeoxyglucose positron emission tomography-computed tomography (PET / CT) is used when there is a need to evaluate the presence of tumors.
• Endoscopic ultrasonography (EUS) and intraductal ultrasonography are more effective for some authors as an assessment tool for the biliary area.[15]