The anterosuperior surface is smooth and convex, almost completely adjacent to the diaphragm; the inferior or visceral surface, instead, is slightly concave and touches the underlying organs: there are three sulci or fissure, two longitudinal ones (right and left sagittal fissure) and a horizontal one, the transverse fissure. The latter represents the hilum, where we find the structures of the pedicle: portal vein and hepatic artery, hepatic ducts, lymph vessels, and nerve branches of the hepatic and biliary plexuses.

The right sagittal fissure consists of an anterior tract (containing the gallbladder, or cholecyst, and therefore named gallbladder fossa) and a posterior one, where the inferior vena cava flows (vena cava fossa). The left sagittal sulcus consists of an anterior part, where we find the round ligament, the remnant of the fetal umbilical vein, and a posterior tract, containing the ligamentum venosum, remnant of the fetal Arantius’ duct. The right lobe is further divided into the quadrate lobe (anterior to the transverse fissure and between the two sulci) and the caudate lobe of the liver (between the sulci, behind the transverse fissure) (Fig. 9.2).

For its position below the diaphragm, the liver is subject to wide respiratory movements and therefore needs a valid anchorage system represented by the peritoneal reflections, otherwise referred to as ligaments.

The right portion of the coronary ligament connects the posterior face of the liver to the posterior abdominal wall; it consists of two layers, the anterosuperior and the posteroinferior ones, separated at the level of the right lobe by the bare area, and merging on the right side, into the triangular ligament. In a similar way, the anterosuperior and posteroinferior layers of the left coronary ligament merge into the left triangular ligament which connects the liver to the relevant hemidiaphragm (Fig. 9.3).

The falciform ligament, cranial portion of the coronary ligament, is a peritoneal reflection connecting the superior face of the liver to the diaphragm, from the anterior margin to the posterior abdominal wall; it looks like an almost sagittal septum, with curved borders, a convex one for the connection to the diaphragm and a concave one on the superior surface of the liver (the name derives from its shape). The falciform ligament continues caudally into the round ligament.

Finally, we find the hepatogastric and hepatoduodenal ligaments (lesser omentum), consisting of two layers of peritoneum, attaching the lesser curvature of the stomach and the duodenum to the inferomedial surface of the liver.

The liver is a special organ: it has a dual blood supply from the hepatic artery (supplying the 20–25 %) and the portal vein (supplying the 75–80 %); the refluent blood flows into the inferior vena cava through the suprahepatic veins (Fig. 9.4). The hepatic artery may originate from the celiac trunk (normally, in 65–75 % of individuals) or the superior mesenteric artery or the left gastric artery: the origin and course of such a vessel are extremely variable. The portal vein arises in the retroperitoneum from the junction of superior mesenteric and splenic veins, behind the pancreatic neck; it enters the hepatoduodenal ligament, up to the hepatic hilum; therein, the vein ramifies into two intrahepatic branches, the right and left one.

The traditional macroscopic anatomy—dividing the liver into two main lobes (right and left) and two accessory or secondary lobes (quadrate and caudate lobe) delimited by well-visible and well-defined fissures, as widely described herein above—has been replaced, in the last decades, by a more functional segmental subdivision based on the intraparenchymal distribution of the hepatic veins and portal venous and biliary branches. The portal venous, hepatic arterial, and biliary system travel together within hepatic segments and lobes (intrasegmental). The main hepatic vein courses between segments and lobe (intersegmental). Such hepatic segmental topography, obviously more complex, is also more complete and comprehensive: it provides a three-dimensional description which is the reason why it is preferred, also considering the increasing number of liver surgeries.

The middle hepatic vein divides the liver into the right and left lobe, completely independent with regard to the portal and arterial circulation and the biliary drainage. The fissure containing the middle suprahepatic vein extends from the median portion of the bed of the gallbladder, anteriorly, to the inferior vena cava, posteriorly; therefore, if in traditional anatomy the falciform ligament is the boundary between the right and left lobe, the new surgical approach considers the fissure for the gallbladder—and more precisely the Cantlie line, a straight, imaginary line going from the fissure of the gallbladder, anteriorly, to the right margin of the inferior vena cava, posteriorly—as the boundary between the two lobes. Each lobe is further divided into four segments by the right and left hepatic veins and by the right and left branches of the portal vein (the term segments has been introduced by the British authors Goldsmith and Woodburn and then spread, with subsequent amendments, by Couinaud). The current subdivision into eight segments is more effective, because each segment has an independent system of arterial supply, and venous drainage, which is essential for surgeons during hepatectomy, lobectomy, or segmentectomy.

In short, the hepatic segments are clockwise: segment 1, functionally independent, in front of the inferior vena cava, coinciding with the caudate lobe; segments 2, 3, and 4 (left lobe); and segments 5, 6, 7, and 8 (right lobe) (Figs. 9.5 and 9.6).