ABSTRACT
The caudate lobe of the liver is anatomically distinct from both the right and the left hepatic lobes. It is interposed among the inferior vena cava posteriorly, the left hepatic lobe anteriorly and superiorly, and the main portal vein inferiorly (Fig. 8) (3). The proximal horizontal portion of the left portal vein (i.e., pars transversal) courses over the anterior margin of the inferior caudate lobe, separating it from the more anteriorly positioned medial segment of the left hepatic lobe (Fig. 6B). The left anterior margin of the caudate lobe is separated from the
lateral segment of the left hepatic lobe by the fissure for the ligamentum venosum (Fig. 8). On the transverse view, the caudate lobe, between the inferior vena cava and the bifurcation of the portal vein, is contiguous with the right lobe. The right inferior margin of the caudate lobe extends in a tongue-like projection, known as the caudate process, between the inferior vena cava and the adjacent main portal vein and the medial portion of the right hepatic lobe. In most persons, the caudate process is small, permitting contact between the main portal vein and the inferior vena cava, and, thus, is not recognized sonographically. The papillary process is a small, ovoid prominence on the anteroinferior aspect of the caudate lobe. Both left and right portal triads give off portal-venous and hepatic-arterial branches to the caudate lobe and receive from it bile duct tributaries. The initial horizontal
Main lobar Separates right lobe from left lobe Cephalic portion: middle hepatic vein Caudal portion: gallbladder fossa Right intersegmental Separates anterior and posterior segments of right lobe Right hepatic vein Left intersegmental Separates medial and lateral segments of left lobe Cranial third: left hepatic vein Middle third: ascending portion of left portal vein Caudal third: ligamentum teres Falciform ligament Ligamentum teres Separates medial and lateral segments of left lobe Ligamentum teres Falciform ligament Ligamentum venosum Separates caudate lobe from lateral segment of left lobe
TABLE 2 ■ Fissures of the Liver
Fissure Usefulness Structures within the Fissure
portion of the left portal vein gives off several branches to the caudate lobe (Fig. 6B). The caudate lobe is drained by a series of small, short, venous channels that extend directly from the posterior aspect of the caudate lobe into the inferior vena cava adjacent to the posterior margin of the caudate lobe. Three major anatomic landmarks-the fissure for the ligamentum venosum, the inferior vena cava, and the pars transversa of the left portal vein-permit sonographic localization of the caudate lobe (3).
