Teaching Case

Surgical liver anatomy.A color and power Doppler ultrasonographic approach.

We examined a 29-year-old normal female subject with no liver congenital anomalies. Her past medical history was negative. There was no history of drug ingestion. All her liver laboratory tests revealed normal results. For the ultrasonographic examination we used a General Electric 700MR unit.

During the last decade liver resection gained widespread acceptance as operative mortality and morbidity have been remarkably reduced and prognosis after adequate tumor removal has been improved. Segmentectomies are based on subdivision of liver parenchyma according to the distribution of portal vein and hepatic artery, using as helpful landmarks the hepatic veins’ position. In the past , liver resections were made according to what could be told liver segment anatomy from the surface view. Today’s surgically relevant segmental anatomy of the liver is based on Couinaud’s three dimensional concept based on both the distribution of portal veins’ branches and the three hepatic veins. This classification divides the liver into eight functional segments, each with it is own vascular inflow, outflow and biliary drainage. The numbering system of these segments has become widely accepted in most countries. As illustrated by the French surgeon Claude Couinaud the middle hepatic vein divides the liver into right and left hemilivers, also separated by main portal vein fissure (passing through inferior vena cava and the long axis of the gallbladder).The left hemiliver is further divided by the left hepatic vein into medial and lateral sections, and the right hemiliver is further divided by the right hepatic vein into anterior and posterior sections. These sectors are divided into eight segments. The eight segments are numbered clockwise on a frontal view. Each segment is therefore a functional unit supplied by a branch of the portal vein coupled by a hepatic artery branch and is bordered by a hepatic vein. Segment I is the caudate lobe. This lobe is unique because it derives its blood from several branches of the right and left portal vein and hepatic artery. It drains directly into the vena cava through a main caudate vein and minor hepatic veins. Segments II and III are the superior and inferior portions of the left lateral sector. Segment IV (the former qaudrate lobe) is the left medial sector. Segments V and VIII are the inferior and superior portions of the right anterior sector. Finally segments VI and VII are the inferior and superior portions of the right posterior sector. With improvement of ultrasonograhic technology including color Doppler flow imaging, u/s examination can now produce real-time mapping of hepatic vessels in relation to the architecture of the liver. The portal branches of four segments of each lobe are seen as letter H (described by Lafortune) when the transducer is placed in an oblique upwardly tilted subxiphoid position for the left lobe and in a sagittal or oblique midaxillary intercostal position for the right lobe. The three hepatic veins form a letter W with an oblique transverse view. As a conclusion we believe that all radiologists and radiographers must adapt the Couinaud’s classification for localizing precisely any liver lesion in preoperative studies and for follow-up examinations if the segmental location of each lesion has already been defined. Such information is critical for the treatment options.