Surgical Anatomy of the Caudate Lobe

Knowledge of anatomy of the caudate lobe and its relationship with the porta hepatis area are mandatory for a correct surgical approach to hilar cholangiocar-cinoma. In fact, the surgical treatment of this disease requires en-bloc resection of the caudate lobe.

Currently the caudate lobe is divided into three parts, according to Couinaud's definition [6]:

- Segment 1 (S1), or caudate lobe, in the strict sense of the word, which corresponds to the portion with left development

- Segment 9 (S9), corresponding according to Couinaud [7] to the portion with right development

- Caudate process, a small portion of parenchyma which represents the infer-omedian extension of segment 9

Nimura [8] has proposed naming Segment 1 on the left: S1l; segment 9 on the right: S1r; caudate process: S1c (Fig. 8). The right and left caudate lobe are separated by the Arantius canal or ligamentum venosum, an embryonic vein coming from the base of the umbilical portion that enters the left hepatic vein, or the common trunk of the left and middle hepatic vein or directly into the inferior vena cava. The right lateral margin of S1r is on the left site of the right posterior portal vein, and the superior margin extends up towards the diaphragm, crossing middle and right hepatic veins.

The biliary branches of the caudate lobe are very variable. They join the left and right hepatic ducts and their confluence. According to Nimura [8], these branches are classified in four groups:

- B1ls, branches that come from the superior part of segment 1 and enter into left hepatic duct

- B1li, biliary branches coming from the inferior part of segment 1 and open into right posterior biliary duct

- B1r, biliary branches coming from segment 9 of Couinaud and open into both the right posterior segmental and the left ducts

- B1c: small biliary branches of the caudate process that join the right posterior duct (Fig. 9)

The small arteries for the caudate lobe originate directly from the right and left hepatic artery.

The portal component is variable: from two to six vessels come from the left portal vein, two or three small vessels come from the right portal vein, finally one or two vessels arise from the main trunk or portal bifurcation.

Venous drainage consists of short hepatic veins, variable in number and size (1-6 mm), that open into the vena cava, with a very short course of a few millimeters. Lastly, some small venous rami (two or three) coming from the right caudate lobe (S1r) directly join the middle hepatic vein.

Middle Hepatic Vein
Fig. 8 Caudate lobe anatomy. The lobe is divided in three parts: left part (Sil); right part, or segment 9 according to Coinaud (Sir); caudate process (S1c). HV, Hepatic veins; U, umbilical portion
Caudate Lobe Liver Diagrams

Fig. 9 Surgical anatomy of the caudate lobe with bile duct, portal vein and hepatic veins. IVC, Inferior vena cava; RHV, right hepatic vein; MHV, middle hepatic vein; LHV, left hepatic vein; CBD, common bile duct; PV, portal vein; 1 r, biliary branch of the right caudate lobe; 1 Is, superior biliary branch of the left caudate lobe; 1 li, inferior biliary branch of the left caudate lobe; 1 c, biliary branch of caudate process. Numerals refer to Couinaud's segmental anatomy

Fig. 9 Surgical anatomy of the caudate lobe with bile duct, portal vein and hepatic veins. IVC, Inferior vena cava; RHV, right hepatic vein; MHV, middle hepatic vein; LHV, left hepatic vein; CBD, common bile duct; PV, portal vein; 1 r, biliary branch of the right caudate lobe; 1 Is, superior biliary branch of the left caudate lobe; 1 li, inferior biliary branch of the left caudate lobe; 1 c, biliary branch of caudate process. Numerals refer to Couinaud's segmental anatomy

+2 0

Post a comment