The caudate lobe, also known as segment I according to Kumon’s classification, is the portion of the liver that lies between the vascular structures: the hilar plate, hepatic veins, and the IVC. Kumon divides the segment I into 3 parts: the Spigel lobe, also known as S1l, which lies below the lesser omentum and extends to the left posterior hepatic part of vena cava; the anterior venous part is the part located in front of the vena cava and to the right of the Spigel lobe, also known as S1r, which is closely associated with the right hepatic vein and the middle hepatic vein; the caudate process is the right portion of the anterior venous part also known as S1c 1.
According to Takasaki, the liver was divided into 4 segments: the right segment, the middle segment, the left segment, and the caudal region. The caudal region occupies about 10% of liver volume and supplied by several small Glissonean pedicles directly from the first branch at the hepatic hilum. This is the region of the liver located in front of the vena cava, and its veins drain directly into the vena cava. However, this part of the liver is only adjacent but not attached to the vena cava. The boundaries of the three lobes of the liver with the caudal region are delimited by triangles as shown in the figure. The anterior triangle of the vena cava separates the left and caudal lobes, and the lateral triangle of the vena cava separates the caudal lobe from the right lobe 9.
Our approach to the caudate lobe is based on these above two anatomical perspectives. In order to find and ligate the caudate lobe pedicles from the hilar plate, we detached the hilum plate, and isolate the right and left Glissonean pedicle. Then we could find and the ligate the pedicle to the caudate lobe, and also created more space for dissection in this hard-to-reached area. The lateral and anterior triangle segment of the vena cava in the figure ? shows us the left and right liver demarcation to separate the caudate lobe from the right and left liver. When approacg to the left side, we can rely on an anatomical landmark is the ligamentum venosum. The liver parenchymal transection line must be close to this ligament to avoid injury to the middle and left hepatic vein. Kumon's Classification allows a 3-way parenchymal resection approach according to our technique from the left side (Spigel lobe), from below (the caudal process) and from the right side (the paracaval portion).
For a successful ICL, in addition to the knowledge of surgical anatomy, the way to approach liver tumor also plays a very important role. Depending on the location and pathology of tumor and the liver function, an appropriate approach and method should be selected to ensure the radical oncology and to limit complications, especially liver failure after an extended liver resection. Regarding the location for a rational approach, Hasegawa et al. 10 classified liver tumors originating from the caudate lobe into 5 types:
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Type 1: Lesions in the Spigel lobe’s upper part
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Type 2: Lesions in the Spigel lobe’s lower part
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Type 3: Lesions around the vena cava (paracaval portion)
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Type 4: Lesions in the caudate process
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Type 5: Diffuse lesions of the entire caudate lobe
Our first patient is a case of HCC, a tumor of type 5 according to Hasegawa’s classification, although the tumor located close to the right hepatic vein, the caudate lobectomy with right hepatectomy could be more radical, but because of cirrhosis and the remaining liver volume was not enough. In the second case, the tumor completely occupied the anterior vena cava of the subsegment I and pushed to the Spigel lobe and could be classified between type 3 and 5. After we removed the entire caudate lobe an frozen section result was a benign lesion. Thus, our choice of ICL in both cases is reasonable in different circumstances.
During isolated caudate lobectomy, there are four main approaches: left-sided approach, right-sided approach, anterior approach, and right and left combined approach. For tumors in the left region (Spigel lobe), the left approach is sufficient, but for large tumors or tumors in the anterior area of vena cava, it is often necessary to combine with the right approach or use the anterior parenchymal opening. Anterior parenchymal opening approach provides good visibility and access for subsegment I resection, especially for large tumors and closely related to the hepatic veins 11,12 but it increases the risk of bleeding and prolongs the surgical time 13,14. A combined left and right approach is recommended for most tumors of caudate lobe 4,15, especially for tumors larger than 4 cm in diameter, which are of primary origin from the paracaval portion or in the entire caudate lobe, or those that are thought to be malignancies, require total caudate lobectomy to remove the tumor.
The exposure and ligation of the short hepatic veins is a difficult task in ICL 4. Ligation and resection of the short hepatic veins release the entire caudate lobe from the IVC and facilitate management of the hepatic veins and control of hemostasis during parenchymal resection. We found that the process of controlling the short hepatic veins was not too difficult after fully mobilized the right and left liver, when combining from both the right and left sides together with fine dissection.
We found that we sould isolate and tape the hepatic veins before performing parenchymal transection because the caudate lobe parenchyma is in contact with the posterior surface of the hepatic veins. So, we could reduce the risk of injuring these veins. The transection of the ligamentum venosum will help control the left and middle hepatic veins easier, but we did not divide this ligament. We blunt dissected and pushed it from the liver for the purpose of using this ligament as a landmark to start transecting the liver parenchyma from the left side.
Resection of liver parenchyma is the most challenging stage, we transected the liver parenchyma and had to ensures not to rupture the tumor, not to damage to the hepatic veins, especially the middle hepatic vein. Because the resection location deep, and close to the hepatic veins, it is easy to damage the hepatic veins. We found that, it is very difficult to control and manage the ịnured vein during this stage. Other authors have used many ways to safely and effectively cut the liver parenchyma such as using hanging maneuver procedure 16, or using dye agents to define the hepatectomy demarcation 3, or using anterior parenchyma resection provides better visibility, but anterior parenchymal resection increases operative time and increases the risk of bleeding 13,14. To secure the parenchymal resection, we suggest the following tactics: first, after a three-pronged approach described above, detachment of the hilum plate and ligation of the pedicles of caudate lobe help to create space for dissection as well as recognize parenchymal ischemic area. The second is selective clamp the right and left glissonean pedicles, respectively when transection parenchyma from both sides and only did the Pringle maneuver if there was severe bleeding; and finally, we note the landmarks of parenchymal demarcation on both sides, on the left is just below the ligamentum venosum and on the right is from the origin following the inferior border of the right hepatic vein, to ensure the best transetion area, and avoid damaging the hepatic veins.