Quadrate lobe

The quadrate lobe of liver is typically found between the left medial and right medial lobes (or their equivalents), ventral to the porta hepatis and dorsal to the gallbladder (if present). Its shape and size are influenced by the position and size of the gallbladder and the liver lobulation pattern of the species.

Species specifics:

• In dogs and cats, the quadrate lobe is distinct and lies between the right medial and left medial lobes. It is a small, flat lobe situated ventral to the porta hepatis and usually houses the fossa for the gallbladder on its right margin. This is consistent with a more lobulated liver seen in carnivores.

• In horses, the quadrate lobe is well developed and located between the left and right lobes. It forms a significant portion of the ventral liver surface and contributes to the left boundary of the gallbladder fossa (even though horses do not have a gallbladder). It is demarcated dorsally by the porta hepatis.

• In ruminants, the liver is less lobulated. The quadrate lobe is smaller and less distinct than in dogs or horses. It is found between the left lobe and the right lobe and contributes to the formation of the gallbladder fossa. It is usually triangular and is located ventrally to the porta hepatis.

• In pigs, the quadrate lobe is well developed and prominent. It is located ventrally and to the left of the gallbladder, between the left medial and right medial lobes. The gallbladder often lies partially embedded in the quadrate lobe.

Vascular and Biliary Relations The quadrate lobe receives vascular and biliary branches from both the left and right hepatic systems, particularly from the left medial and right medial branches of the portal vein and hepatic artery. Its bile ducts usually drain into the left hepatic duct or common hepatic duct, again depending on the species.