Hepatic Vein System
In general, the hepatic veins drain the liver through suprahepatic segmentation. As described by Couinaud, suprahepatic segmentation is exactly reflected by the external anatomical morphology of the liver. Consequently, the left hepatic vein drains the an
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Hepatic Vein System
In general, the hepatic veins drain the liver through suprahepatic segmentation. As described by Couinaud, suprahepatic segmentation is exactly reflected by the external anatomical morphology of the liver. Consequently, the left hepatic vein drains the anatomic left lobe and the middle and right hepatic veins drain the right lobe, while the caudate lobe is the drainage region of short subhepatic veins. The right hepatic veins constantly drain segments VI and VII and different parts of segments V and VIII, depending on the size or diameter and on the number of right hepatic veins. In most cases, the region of right hepatic vein drainage is largest, representing 30-50% of liver volume. The middle hepatic vein always at least partly drains segments IV and V, and to a varying degree segment VIII. In about 10% of livers, the middle hepatic vein also drains segment VI. The left hepatic vein constantly drains segments II and III. In about 15% of cases, the left hepatic vein drains the anteromedian part of the left liver, i.e. segment IV. Short subhepatic veins drain segment I and partly the paracaval region (segment IX). There are anastomoses between the hepatic veins which play an important role in liver physiology and surgery. Anastomoses may help drain the neighbouring region, however it is rather time consuming for the drainage to be thoroughly established after ligation of a larger vein. Surgeons know that when a considerable part of the liver tissue is deprived of its original main venous drainage after resection, a congestion with considerable bleeding on the resection surface may result from the release of the vascular occlusion in the hepatoduodenalligarnent.
Right Hepatic Veins There is often more than one right hepatic vein. There can be up to four smaller veins draining segment VII and/or segment VI but predominantly the right paracaval region (caudate process or segment IX), while the presence of two or three rather large hepatic veins is not quite so rare and is surgically important. There have not been enough studies carried out yet describing the existence and number of right hepatic veins to reliably indicate their frequency. MRI, angiography combined with CT, and in particular intraoperative US investigation are useful tools for presenting the position and course of the hepatic veins. A complete mobilisation of the right liver is essential during an operation to expose the entrance of the right hepatic veins into the inferior vena cava.
One Right Hepatic Vein The superior right hepatic vein is set deep in the right liver and its flow axis determines the right portal fissure and the border between the right posterior and the right anterior sectors. The superior right hepatic vein has several branching patterns; the inflow angle of the main stem into the antero-lateral face of the inferior vena cava is usually about 70 degrees, although it can sometimes be sharper. There is often one strong stem of the superior right hepatic vein gathering branches from the neighbouring segments VII,
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