Surgical treatment of perihilar cholangiocarcinoma (PHC) is one of the main challenges in hepatobiliary surgery, whereas the type and extent of the resection to be performed is still a matter of debate. There is agreement on the importance of achieving complete resection (R0-resection) as oncologically adequate therapy, in respect with the ductal margins as well as the circumferential margins.1–3 Resectability is usually assessed using the Bismuth-Corlette-classification by which tumor extension into the right and left biliary tree is taken into account. The predominant side of the tumor usually determines whether a right or left resection is planned. However, like any other solid tumor, the growth of PHC should not only be considered in 2 dimensions, but in 3 dimensions, revealing that anterior extension into segment 4 and posterior extension into segment 1 is equally important.4 Hence, for complete excision, the goal is to achieve locoregional clearance of the tumor along the laterolateral axis as well as the antero-posterior axis implying that segment 1 and segment 4 should be part of the resection.,5 This suggests that left hemihepatectomy (removal of liver segments 1–4, classified as H1234 according to the most recently suggested “New World” terminology) has an advantage because segment 4 is anatomically part of the left liver lobe.6 In contrast, in a right-sided resection, segment 4 and 1 have to be added to the functional right liver lobe (segment 5–8), requiring extended right hemihepatectomy (right trisectionectomy according to Brisbane classification or H45678 according to New World terminology) rather than standard right hemihepatectomy (H5678).6 This obviously translates into a smaller liver remnant, typically only retaining the left lateral segments. The 3-dimensional growth pattern of PHC also applies to the tissues and stuctures surrounding the tumor, that is, the liver parenchyma and the vascular structures at the porta hepatis which determine the circumferential margins1–5 Consequently, complete removal of PHC whether undertaken from the right or left side, will require:
- - resection of the hilar biliary confluence
- - en-bloc with partial liver resection including segments 1 and 4
- - parts of the portal vein and/or hepatic artery branches when involved
- - locoregional lymphadenectomy.
The criteria for choosing right or left-sided resection are based on the predominant side of the tumor mass, the hilar biliary anatomy, vascular involvement, and the proximal level of transection of the bile duct.2,4 These decision criteria may be questioned or even overruled by the need to preserve sufficient future liver remnant (FLR) volume and function, to prevent posthepatectomy liver failure.
Another issue that has been argued when defining surgical strategy is the length of the hepatic duct on the left versus the right side, influencing oncological radicality of the resection. There are corresponding data of anatomical and radiological studies showing that the extrahepatic portion of the hepatic duct on the left side is longer than that on the right side.7 Hence, extended right hemihepatectomy dividing the bile duct just until the umbilical fissure or even extending transection to the segmental ducts (B2 and B3) left of the umbilical fissure, may provide the longest ductal margin.8 The attractiveness of this approach is – next to having a high likelihood of achieving a R0-resection – a technically straightforward and anatomically correct resection with a small transection plane on the liver side. In contrast, the left approach entailing left extended hemihepatectomy is demanding and not at all a routine procedure.9 Due to the great variation of the intrahepatic vascular and biliary branching patterns as well as missing anatomical landmarks on the liver surface, intraoperative orientation may be difficult in left extended resection even under ultrasound guidance. Thus, vascular supply of the remnant liver (segments 6 and 7) may be compromised with an increased risk for areas of ischemic necrosis and impaired biliary drainage. After left extended hemihepatectomy, the number of bile ducts to be anastomosed is usually higher (it may reach up to even eight or nine) than after right extended resection where, depending on the level of transection usually only 1 or 2 bile ducts (ie, B2 and B3) need to be reconstructed using a Roux-en-Y loop.
Additionally, involvement of vascular structures is more critical on the right side as the right hepatic artery (RHA) and its bifurcation to anterior and posterior branches are typically located directly behind the tumor bearing hilar bile ducts but in front of the portal vein.10,11 The left hepatic artery, however, usually runs along the medial rim of the hepatoduodenal ligament, distant to the tumor, whereas in case of a replaced LHA arising from the left gastric artery, tumor involvement is unlikely. From a surgical point of view, arterial reconstruction of the RHA is challenging as after excision of the bifurcation of the right posterior and anterior branches, the main stem of the RHA has to be anastomosed directly to the much smaller, right posterior branch supplying segments 6/7. Therefore, concomitant resection of the right arterial complex with right hepatectomy offers an advantage.
Right-sided resection also has an advantage regarding the portal vein because the left trunc of the portal vein is much longer than the right, facilitating reconstruction when the portal vein bifurcation needs to be resected.11 A mismatch of the diameter of the umbilical portion of the left portal vein with the main portal stem is easily dealt with by creating a bevelled anastomis. The right portal vein is much shorter or may even be missing in case of the main stem ending in a trifurcation, resulting in tumor infiltration directly into the right posterior branch, requiring intrahepatic dissection of the posterior branch until a free margin has been achieved. Reconstruction is more cumbersome as the posterior branch in turn may bifurcate intrahepatically to segments 6 and 7, whereas the portal vessel walls are often much thinner in that location.
Provided there is a sufficient FLR, then an extended right resection should be preferred because this is a technically straightforward procedure and the likelihood to achieve negative margins is higher owing to the longer left hepatic duct. In PHC in which livers have usually sustained cholestatic damage, a larger volume of the FRL, preferably >40%, is required to forestall postresectional liver failure.12 A volume deficit of the left liver remnant can readily be compensated with the use of volume modulating techniques such as portal vein embolization (PVE).13 In a large series in Asia, PVE was used in 60% of patients with a 90-day mortality of 2% suggesting a benefit of a liberal use of PVE to increase volume and function of the liver remnant.14
So far there are no clinical studies on the necessary width of the ductal safety margin, whereas in literature there is only differentiation between R1 or R0. Margin positive resections (R1) are associated with a higher rate and a different pattern of recurrence showing an up to threefold higher incidence of locoregional relapse. Yet also after R0 resections, early local tumor recurrence has been reported in up to 25% of patients and, although less frequently, a considerable number of local recurrences are noted even years after resection.15
These recurrences may be explained by the discontinuous ductal growth of PHC leaving skip lesions in the remaining bile duct after resection.16 It has been shown that deposits of invasive carcinoma, mainly responsible for early recurrence, may be found in up to 10 mm beyond the macroscopic margin of PHC. These findings suggest a ductal safety margin of ideally, at least 10 mm. Although this will be difficult to attain in most cases, the greater length of the left hepatic duct will increase the chance to achieve a larger ductal safety margin favoring a right-sided approach.
Published outcome data, mainly based on retrospective analyses, showed a tendency toward a better survival after right liver resection. But this advantage vanished when 90-day mortality is not excluded and data of the entire group of patients are considered.17,18 Hence, the supposed better results in right resection are most likely due to the somewhat higher probability to achieve an R0 resection rather than because of a true oncological superiority of this approach per se.
In conclusion, the choice of either right- or left-sided liver resection is determined by the predominant anatomic location of the tumor mass in conjunction with vascular involvement and individual biliary anatomy at the liver hilum. With extended right hemihepatectomy, the longer extrahepatic left hepatic duct provides a greater chance to achieve a tumor free, proximal ductal margin. Although the left hepatic artery usually remains free, the RHA and its branches carry a higher risk of tumor involvement and as reconstruction is more demanding, removal with right-sided resection offers an advantage. Reconstruction of the left portal vein after excision of the portal vein bifurcation is also more simple with right-sided hemihepatectomy than anastomosing the shorter right portal vein when coming from the left side. Extended right hemihepatectomy is more or less a routine procedure and in particular, biliary reconstruction is technically more straightforward than after left hepatectomy. Hence, provided there is a sufficient FLR – the liberal use of PVE is recommended when FLR is <40% – extended right hemihepatectomy is preferred over left-sided hepatectomy.
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