Ultrasound Correlation

By positioning an ultrasound transducer appropriately, the four Couinaud segemtns of the left and right liver lobes can be identified by the portal braches leading to their centers and the hepatic veins at their periphery.

With improvement of ultrasound technology including pulse and color flow Doppler imaging, intraoperative ultrasound examination can now produce detailed views of the architecture of the liver including real-time mapping of hepatic vessels in relation to focal hepatic lesions. Thus, final assessment for resectability and determination of resection planes according to Couinaud segmental anatomy can now be made in the operating room quickly, cheaply, and with great precision. The portal branches to the four segments of each lobe are seen as letter H's described by Lafortune when the transducer is positioned in the two areas shown below. [Lafortune].

Fig 5-1 The segments of the right lobe are best seen by placing the transducer in sagittal midaxillary intercostal (A) or transverse subcostal position (B)[Lafortune].

Ultrasonographic View of Right Liver Lobe Segments

Fig 5-2 Above is the ultrasonographic view of the portal branches to the Couinaud segments 5, 6, 7, and 8 obtained when the probe is viewing sagittally from position A shown in the 3D line drawing.

The branches to segments 5 through 8 can be seen radiating from the right portal vein with the crossbar of the letter H formed by the right portal vein (rpv). The portal branches to segments 7 and 8 are superior to segments 6 and 5 respectively with segments 5 and 8 anterior to the right hepatic vein and segments 6 and 7 posterior to it.

Ultrasonographic View of Left Liver Lobe Segments

Fig 5-3Above is the ultrasonographic view of the portal vessels locating the central portions of the Couinaud segments of the left liver lobe. This view is obtained when the transducer is viewing transversely from position B in the line drawing.

The segments of the left lobe are best seen by placing the transducer inferior to the xiphoid process and aiming obliquely in a posterosuperior direction and towards the patient's left shoulder. The branches forming the sideways letter H are seen by looking clockwise from the prominent left portal vein in the lower left corner of the picture to the other three corners of the H which are the branches to segments 4, 3, and 2 respectively. The crossbar of the H corresponds to the umbilical portion of the left portal vein. Each segment may actually receive multiple portal branches (especially segment 4). Extending superficially from the umbilical portion of the left portal vein is the falciform ligament which often is seen as an echogenic line projecting between segments 3 and 4 anteriorly. The ligamentum venosum can also be seen on ultrasound as an echogenic line projecting posteriorly separating the lateral aspect of segment 1 from the medial aspect of segment 2.

Ultrasonographic View of Hepatic Vein Confluence with Inferior Vena Cava

Fig 5-4 Above is the ultrasonographic view of the confluence of the right (rhv), middle (mhv), and left (lhv) hepatic veins with the IVC.

The hepatic veins can also be seen from the subxiphoid position if the transducer held transversely is aimed in at the patient's right shoulder. From this position, they can be seen joining the inferior vena cava. The usual pattern is to have 3 hepatic veins (right, middle, and left). It is relatively common to have more than 3 hepatic veins and often the hepatic veins may have common trunks [Makuuchi, Masselot, Nakamura]. When more than 3 hepatic veins are present, the others are usually smaller than the 3 main ones and are considered accessory veins. The segmental boundaries are still determined by branches of the 3 main hepatic veins.

The views shown here are only a starting point to allow the sonographer to locate all of the segments. After finding the center of each lobe by identifying the portal vein, the examiner must define the location of masses in each segment by turning the probe perpendicular to the portal vein and exploring the periphery of the segment defined by the hepatic veins that drain that segment. In this way, the precise location of liver lesions can be imaged and resectability can be determined.

Last modified: Wed Jun 2 11:50:08 CDT