Upper Transversal Hepatectomy for Pediatric Liver Tumors Based on the Inferior Right Hepatic Vein.

INTRODUCTION: Tumors located at the hepatocaval junction with the involvement of hepatic veins conventionally warrant major liver resections. Appreciation of sizeable inferior right hepatic vein can allow preservation of uninvolved inferior segments of the liver. OPERATIVE TECHNIQUE: Preoperative and intraoperative identification of sizeable inferior right hepatic and other accessory or communicating veins in combination of intra-operative ultrasound guidance for resection to preserve inferior segments of the liver with adequate venous drainage. Application of upper transversal resections for pediatric liver tumors at the hepatocaval confluence was illustrated with description of operative technique and patient selection.
CONCLUSIONS: Parenchymal preserving surgeries are possible for pediatric liver tumors located at the hepatocaval confluence by identification of accessory draining veins to the inferior segments. This along with meticulous parenchymal dissection with ultrasound guidance to preserve all uninvolved veins is key to safe upper transversal resections. Copyright:

INTRODUCTION

Tumors located at the junction of the hepatic veins (HVs) and the inferior vena cava (IVC) are surgically challenging to resect. Such lesions invariably involve one or more HV that conventionally results in a hemihepatectomy or extended liver resections. This entails the removal of large volume of functioning liver parenchyma noncommensurate with the size of the tumor. Techniques to avoid major liver resections have been described in adult liver surgery that relies on the presence of accessory veins and communicating veins (CV) that drain the inferior segments of the liver. However, no such application in pediatric liver resections could be found in the literature. The following description contains the anatomical basis for resection of upper segments of the liver, its technical details, and applications in pediatric tumors.

DESCRIPTION OF OPERATIVE TECHNIQUE

Before any liver resection, meticulous appraisal of the radiology is mandatory. Triphasic contrast computerized tomography is our imaging modality of choice for pediatric liver tumors. A review of scans is done for the location of the lesion, proximity, and involvement of the HV and IVC [Figure 1]. More important to conservative liver resections for tumors at the hepatocaval confluence is the acknowledgment of the presence of accessory draining veins for the residual inferior segments of the liver. A large inferior right hepatic vein (IRHV) is often present, especially so when the right hepatic vein (RHV) is occluded by tumor [Figure 2]. The relative size of IRHV and RHV is accounted for when deciding the safety of RHV resection without reconstruction. Note should be made of accessory veins draining directly into the IVC, CV between major HVs and sizeable tributaries from the segments to be preserved to the HVs that would not be sacrificed. If the HVs are completely occluded by the tumor, attention should be toward areas of liver congestion if any. If the inferior segments are congested, either a major hepatectomy is warranted or HV reconstruction if inferior segments are to be preserved.

Figure 1

Computerized tomography assessment of tumor - hepatic vein relation. (a) Metastasis from Wilms tumor in segments 7/8 and 8/4a. The right hepatic vein was involved and the middle hepatic vein was in contact with the Seg8/4a lesion. (b) Hepatoblastoma involving the right hepatic vein and in close contact with the middle hepatic vein

Figure 2

Large caliber inferior right hepatic vein

A bilateral subcostal incision and a self-retaining retractor at the costal margins provide operative exposure. This is essential for working at the hepatocaval confluence. The liver is mobilized by releasing its attachments to the diaphragm and the retroperitoneum. Suprahepatic and the retrohepatic IVC are exposed without division of any veins draining into the retrohepatic portion of IVC. Hepatocaval ligament is divided when present.

Next, the tumor is assessed peroperatively for its relation with the HV by gross examination and with the aid of intraoperative ultrasound (IOUS) [Figure 3]. This should reveal also the draining veins of the inferior segments of the liver [Figure 4]. With this, the final decision is made regarding the extent of surgery, the HVs to be sacrificed, and the vertical extent of resection to encompass tumor with negative margins as well as to safeguard the drainage of the residual liver.

Figure 3

Intraoperative tumor location at the caval confluence. (a) Wilms tumor metastasis in S7/S8 (white ring) and S8/S4a (black ring). (b) Hepatoblastoma involving right hepatic vein at the hepatocaval confluence

Figure 4

Intraoperative demonstration of right hepatic vein and large nferior right hepatic vein after the division of hepatocaval ligament

Parenchymal transection is done using a combination of Kelly-Clysis, bipolar vessel sealers, and ultrasonic cavitation devices. We do not routinely use the Pringle maneuver. Real-time IOUS guidance is essential in delineating tumor-vein relations and the horizontal and vertical extent of resection. Unlike vertical hepatic resections, visualization during deeper parts of transection becomes difficult and the parenchyma does not open up like a book as dissection proceeds. Multiple traction sutures across the proposed line of division facilitate exposure at the depths of resection with traction given selectively at the point of dissection. The second technique that greatly helps is simultaneous division along the entire length of the transection line rather than continuing at a single point. All uninvolved veins irrespective of their caliber are preserved. This translates into the fact that the deep margin of resection may not be the IVC and retroperitoneum in all cases and may indeed be the partially transected segments of the liver to safeguard outflow of the remaining segments. Again using IOUS, the depth of resection is kept close to the tumor to prevent damage to small CVs within the uninvolved parenchyma that may have not been appreciated.

At the end of transection, the specimen is oriented and the attention is turned toward checking for bile leaks by infusing saline after cannulation of the divided cystic duct and clamping of the bile duct distally. The residual liver is checked for the presence of congestion [Figure 5]. A single soft drain is placed at the end of the procedure.

Figure 5

Completed upper transversal hepatectomy. (a) Preservation of inferior segments – S6, S5, and S4b without congestion. (b) Preserved middle hepatic vein and tributaries of the left hepatic vein while resecting part of S4a

As an illustrative example of this technique, a 2-year-old girl with metastatic liver lesions in S7/S8 and S8/S4a from Wilms tumor was operated after a favorable response to chemotherapy. The lesions involved the RHV and were in close contact with the middle hepatic vein (MHV) [Figure 1a] with a thick uninvolved IRHV [Figure 2]. After intraoperative confirmation of tumor location and its relation to the HVs [Figure 3a], IOUS-guided resection was done sacrificing the RHV and lifting the Tumor off the MHV. S4a tributary of left hepatic vein (LHV) was encountered which was divided [Figure 5b]. Care was taken to preserve the IRHV [Figure 4] and other short HV by keeping the Horizontal part of transection above the plane of IRHV. S7, S8, and part of S4a were excised and no congestion was seen in the residual inferior segments [Figure 5a]. The surgery lasted 150 min with a blood loss of 120 ml. The child was discharged on postoperative day 6 uneventfully. Histopathology revealed no residual viable disease. Conventionally, this patient would have required an extended right hepatectomy leaving a future liver remnant (FLR) of 22%, while an upper transversal resection provided a FLR of 72%.

DISCUSSION

Tumors at the hepatocaval confluence are defined as those in contact with the terminal 4 cm of the HV before its drainage into the IVC.[1] However, this was defined for adult livers and no such descriptions are available for pediatric livers. Tumors at the hepatocaval confluence conventionally require extensive liver resection due to the involvement of one or more HVs. It is a common belief that unless standard “vertical” liver resections are performed for these tumors with HV involvement, it would lead to congestion of inferior segments. Vascularized but congested liver segments lead to transection surface bleeding and potentially liver failure.

Conventionally, HV reconstruction was performed when inferior segments are preserved while resecting the HVs. With the demonstration of alternate drainage paths, one can avoid reconstructing the HV as well. In a single-institution study, 29 conservative liver resections were performed resecting one or more HVs without reconstruction.[1] Communicating or accessory draining veins were demonstrated on preoperative imaging and/or IOUS. They displayed no increase in morbidity of these procedures while avoiding major hepatectomies or staged resection on account of inadequate FLR. At the same time, oncological outcomes were also similar.

Most important among the accessory veins is the IRHV. Large IRHVs are found in 10%–28% of the livers and in much higher frequency when the RHV is involved by the tumor.[23] To increase the safety of such resections in the absence of sizeable IRHV, preoperative RHV embolization can be carried out. Nagino et al. performed an extended left hepatectomy with RHV resection after preoperative portal vein and RHV embolization when the IRHV was not large enough, to increase the safety of resection with successful results.[4] This decision can be based on the pattern of RHV as classified by Nakamura and Tsuzuki.[5] Here, the relative sizes of RHV and IRHV are used to define the primary drainage of the posterior section of the right liver. We considered it safe to preserve inferior segments based on the IRHV if its caliber was same or larger than the RHV. However, when the IRHV was smaller than the RHV, reconstruction of RHV or a more extensive resection is resorted to if congestion of residual segments develops after RHV clamping. Alternatively, if portal flows of the segments to be preserved reverse after clamping the HVs to be resected, the outflow is deemed to be insufficient and HV reconstruction is mandated.

In the absence of demonstrable IRHV, Torzilli et al. based conservative liver resections with HV involvement based on skillful IOUS identification of CVs between adjacent HVs.[1] However, they are small caliber veins and demand considerable expertise on the part of the sonologist to identify them and on the surgeon to preserve. Such veins in pediatric livers are very difficult to identify and preserve. CVs become prominent when HVs are occluded by disease and are present inferior to the lesion. We keep our parenchymal transection at depth, close to the tumor to prevent damage to identified and unidentified CVs. In the presence of other sizeable accessory drainage veins, one can avoid steering the resection path along the CVs. However, when no accessory drainage paths can be demonstrated, either a conventional major hepatectomy is indicated or HVs have to be reconstructed if the FLR is insufficient.

For tumors at the hepatocaval confluence, depending on the HVs involved, Torzilli et al. have described novel resections. When S7, S8, and S4a were involved, they described the upper transversal hepatectomy sacrificing both the RHV and MHV if required. The remnant inferior segments (S6, S5, and S4b) being drained by the thick IRHV and CVs between the sacrificed HVs and the LHV.[6] For tumors involving S7 and S8, mini upper transversal hepatectomy was described sacrificing only the RHV.[7] Similarly, for upper central tumors (S8 and S4a), mini mesohepatectomy was defined sparing the S5 and S4b with MHV sectioning that would have otherwise required at least a central hepatectomy.[8] These resections were termed as “radical but conservative” liver resections that are in essence more complex surgeries but preserve majority of the uninvolved liver parenchyma.

There is no mention of such transverse hepatic resections of superior segments preserving the inferior segments of the liver in pediatric patients. Conventionally, in hepatoblastoma, which is the most common primary liver tumor in children, only anatomical resections were allowed. A large recent study demonstrated the feasibility and safety of nonanatomical resections in hepatoblastoma and its purported advantages.[9] However, in this series, all nonanatomic resections were performed for inferior segments, while tumors in superior segments underwent formal anatomical liver resection. With the recognition of the role of IRHV and performance of upper transversal resections, even tumors located in superior segments can be offered parenchymal sparing procedures.

Pediatric livers have an immense capacity for regeneration and thus limited resections have not yet been popular. However, there are few situations where a limited resection would provide benefit. One scenario is a relatively small-sized tumor in the superior segments with or without the involvement of the RHV and MHV that would require an extended right hepatectomy. An upper transversal hepatectomy would provide a simpler surgical alternative with the preservation of three additional segments. Second, such resections allow for repeat resections rather than resorting to liver transplant in case of recurrences if an extended liver resection was performed.[9] The next situation is the involvement of all three HVs by a virtue of a tumor at the hepatocaval confluence. This is considered an indication for liver transplant in hepatoblastoma without thought about atypical resection or HV reconstruction.[10] Here, IRHV can be used to maintain drainage of the posterior section of the liver while sacrificing all three HVs and thus expanding the indication of resection. The other tumors for which these procedures have been applied were for metastatic liver lesions from other solid pediatric tumors. In metastasis, a margin negative resection is sufficient, and parenchymal-sparing surgery should be the aim as much as possible. The reduced morbidity of a lesser resection over an extended resection would allow the delivery of systemic therapy without delay in the metastatic setting. Two of these indications are highlighted by the choice of cases in our illustrations. In the pediatric population, an inadequate FLR is rarely encountered given the robust regenerative capacity of the liver. However, those with prior hepatic resections, knowledge of such procedures may allow resections rather than liver transplantation.

The application of upper transversal resections for pediatric liver tumors is technically feasible when a sizeable IRHV can be demonstrated and preserved. However, they are challenging surgeries due to the nonplanar surface of transection and more often than not without ischemic demarcation to guide the resection. IOUS is extremely valuable for real-time navigation around the tumor and preservation of future drainage of the liver after HV resections. Liver mobilization should be done carefully to preserve the IRHV. Since the transection plane encounters major HVs to be divided or preserved, much more meticulous dissection is demanded due to the fragile nature of these structures.

CONCLUSION

Upper transversal resections with HVs resections for tumors at the hepatocaval confluence in pediatric liver tumors are an alternative to major hepatectomy when an adequate caliber IRHV can be demonstrated. The demand for such procedures is more in adult liver tumors where FLR is a greater concern and even though anatomical resections remain standard of care in pediatric tumors, lesser resections have a role for liver metastasis with emerging evidence for hepatoblastomas as well. Careful pre-operative assessment for the presence of accessory veins, tumor – HV relation on the cross sectional scan combined with meticulous intra-operative parenchymal dissection to preserve all uninvolved veins with IOUS guidance are key to safe upper transverse resections.

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Conflicts of interest

There are no conflicts of interest.