Segment-oriented anatomic liver resections

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Chapter 92 Segment-oriented anatomic liver resections

Charbel Sandroussi, Paul D. Greig

Overview

Decreased intraoperative blood loss and preservation of parenchyma are key contributors in recent advances in liver surgery that have resulted in reduced morbidity and mortality in liver resection. The understanding of the segmental anatomy of the liver has been pivotal in the evolution of a safe liver surgery (Scheele et al, 1995). Segmental liver resection offers maximum preservation of liver parenchyma with minimal blood loss and without compromising oncologic safety (Agrawal & Belghiti, 2011; Billingsley et al, 1998; Bismuth et al, 1988; Machado et al, 2003; Polk et al, 1995). The ability to resect one or more segments, rather than the entire lobe, allows parenchymal preservation in patients with diseased parenchyma or in re-resection patients with limited residual volume. Segmental vascular inflow control facilitates the resection by precisely mapping the transection plane. In addition, anatomic resections that involve the removal of a hepatic segment confined by tumor-bearing portal tributaries for the eradication of intrahepatic metastases in the vicinity of the primary tumor represent an oncologic approach to liver resection for some malignant tumors (Agrawal & Belghiti, 2011; Liau et al, 2004).

Anatomy and Terminology

The current understanding of the segmental anatomy of the liver has come from the original 1952 descriptions of Claude Couinaud (1952a, 1952b, 1956). Based on his analysis of vascular and biliary casts of the liver, Couinaud determined that the human liver consists of eight segments, each with its own portal triad—vein, hepatic artery, and hepatic duct—and hepatic venous outflow. Subsequently it has been shown that each segment can be resected independently (Bismuth et al, 1982). These segments have evolved to become the standard for hepatic nomenclature. This so-called Brisbane terminology (Pang, 2002) eliminates confusing lobes and sectors used in the American, European, and Japanese descriptions of liver anatomy. The terms hemiliver (first-order division), section (second-order division), and segment (third-order division) are not interchangeable; these provide universal terminology for better communication among liver surgeons.

The first-order divisions are right liver (segments V through VIII) and left liver (segments I through IV), or hemiliver, the boundary of which lies along the Cantlie line marked by the path of the middle hepatic vein (MHV), from the middle of the gallbladder fossa to its termination in the inferior vena cava (IVC) (Fig. 92.1). The second-order division into liver sections is based upon hepatic arterial supply and biliary drainage. The sections are derived from the primary divisions of the major right and left portal triads. The right hemiliver is divided into sections known as the right anterior (segments V and VIII) and right posterior (segments VI and VII), separated by the right hepatic vein (RHV). The left hemiliver is divided into left lateral (segments II and III) and left medial (segments IVa and IVb) sections by the umbilical fissure and falciform ligament. Together segments II and III are often erroneously referred to as the left lateral segment.

FIGURE 92.1 Diagram depicting the relationships of the eight liver segments with the major hepatic veins and portal veins of the idealized liver.

The third-order division, segments I through VIII, is defined by hepatic arterial supply and biliary drainage. The axial plane is at the level of the intersection of the hepatic veins and the axial plane of the bifurcation of the portal vein (Table 92.1 and Fig. 92.2). When considering a segmental resection, it is important to identify the common anomalies that may determine resectability. The biliary and arterial anomalies are the most common: about 30% of patients have a major arterial anomaly, and up to 50% have nonstandard biliary anatomy.

Table 92.1 Description of the Anatomic Boundaries of Each Segment

FIGURE 92.2 A, Axial computed tomographic (CT) scan image through the upper liver, demonstrating the anatomic boundaries of segments I, II, IVa, VIII, and VII. B, Axial CT scan image through the lower liver, demonstrating the anatomic boundaries of segments I, III, IVb, V, and VI. LHV, left hepatic vein; MHV, middle hepatic vein; RHV, right hepatic vein; RPV, right portal vein.

Patient Selection

A liver resection based on the segmental anatomy should be the first consideration for any liver resection. Excluding the fenestration of liver cysts or small “wedge excisions” of superficial lesions, an understanding of the patient’s segmental liver anatomy is essential to a safe, controlled resection. This technique is applicable for all types of livers and indications for resection (Hasegawa et al, 2005).

Achieving balance between parenchymal sparing and radical oncologic clearance is of the utmost importance in hepatocellular carcinoma (HCC) patients with cirrhosis. Segmental liver resection forms a bridge between major hepatectomy and nonanatomic resection to preserve maximum liver volume and prevent postoperative liver failure (Agrawal & Belghiti, 2011; Wakai et al, 2007). Replacement with nonanatomic resection should be done only when the anatomy is unsuitable, or when the residual liver would be at high risk for complications. Segmental liver resection is preferred in patients who have colorectal metastasis with multifocal lesions and are undergoing preoperative chemotherapy, which is frequently associated with steatosis and hepatic cirrhosis (DeMatteo et al, 2000).

Preoperative Planning

Variable anatomy from patient to patient confounds the preoperative planning of liver resection. Seldom does any patient have the classic vascular anatomy as depicted by the idealized diagrams. The planning of a segment-based resection must be individualized for the specific anomalies, and their relationship to the plane of transection is particularly important. The assessment of suitability of the operation requires a precise mapping with attention to vascular and biliary anomalies. Resection has been facilitated by the precision digital imaging provided by computerized tomography (CT), magnetic resonance imaging (MRI), and ultrasound (US), allowing the surgeon an interpretation of intrahepatic vascular and biliary anatomy, facilitated by the ability to manipulate the images using widely available software. With the appropriate protocol for arterial and venous enhancement, the third- and fourth-level vascular structures can be accurately defined. Furthermore, the ability to easily scroll through reconstructions in the axial, coronal, or sagittal planes allows the surgeon to analyze and define the anatomy. More advanced, three-dimensional reconstructions of the liver allow the surgeon to dynamically view the anatomy by rotating the liver along a vertical axis, centered on the IVC, or along a horizontal axis, through the bifurcation of the porta. Based on the segments involved by the disease process, their relationship with the segmental hepatic venous outflow and portal venous inflow, which is representative of the arterial and biliary triad structures, can be determined. One technique for planning is to first determine which hepatic veins require resection or preservation, and at what level for an adequate margin, and then to consider the portal triads that need to be included as a basis for the segmental resection.

For a donor right hepatectomy, the presence of single or multiple right portal veins, hepatic arteries, and hepatic ducts impacts the suitability of the donor graft. For example, the presence of the segment V and VIII portal pedicle, arising from the left portal pedicle, and the size of the hepatic veins of segments V and VIII could influence the decision to include the MHV with the graft.

Other technology is being developed, and more sophisticated software is available, that will facilitate the preoperative planning of liver resection. These easily manipulated, three-dimensional reconstructions create a virtual reproduction of the liver that can be used to determine the proposed plane of transection, taking into account the minimum resection margin and residual liver volume. Some facilities that use such technology include the University of Toronto and the University of Illinois at Chicago. The MeVIS imaging system (MeVisLab, Bremen, Germany) is widely used. Some of these systems have been extended to facilitate real-time, image-guided resection by coupling the preoperative images of the virtual liver to a real-time liver and instrument tracking system. Systems being investigated include those under development by Pathfinder Therapeutics (Nashville, TN) and the Medical University of Graz, Austria. These advances offer significant potential for increased precision of preoperative planning for segment-oriented liver resections and intraoperative application to facilitate image-guided surgery.

General Operative Principles

Preoperative Assessment and Anesthesia

The preoperative assessment and preparation of the patient for a liver resection have been described in Chapter 2. Comorbidities should be identified and optimized. Careful assessment of liver function is important, particularly in those with intrinsic liver disease. Preoperative decompression of an obstructed biliary tree should be considered for improving postoperative liver function (Belghiti & Ogata, 2005). Volumetric analysis should be performed in patients with potentially marginal residual liver size and function. Preoperative portal vein embolization (PVE) may facilitate the safety of a complex or extended liver resection by inducing regeneration of the potential contralateral remnant liver segments (Abulkhir et al, 2008). Particular attention should be paid to the reduction of the central venous pressure during transection to reduce blood loss, and measures to prevent hypothermia are also important. The appropriate prophylaxis of infections and venous thromboembolism is required.

Exposure and Mobilization

For a segment-oriented liver resection, open operative exposure can be achieved through a variety of incisions. The most common incisions include the right subcostal with midline extension cephalad (hockey stick) or its modification (J-shaped), or a bilateral subcostal incision with midline extension cephalad (“Mercedes” incision) or without (chevron incision). For access to the infrahepatic IVC, right kidney, duodenum, and retroperitoneum, a midabdominal transverse incision to the umbilicus with midline extension offers generous exposure. A long midline incision may be used for selected liver resections; a right thoracoabdominal incision is seldom required.

One principle to consider in selecting the appropriate incision is whether exposure of the suprahepatic IVC and the origin of any of the hepatic veins is needed. If so, an incision that extends cephalad to the right of the xiphoid process to the junction with the costal margin is valuable. This can usually be achieved without resection of the xiphoid process. Adequate exposure of the liver, including the porta and suprahepatic structures, is facilitated by a retractor fixed to the operating table, which provides for substantial cephalad and somewhat anterior retraction of the costal margins, especially the right. Suitable retractors are the Omni-Tract (Omni-Tract Surgical, St. Paul, MN), the Iron Intern (Automated Medical Products, Edison, NJ), and similar retractors made by various other manufacturers, such as the Bookwalter (Codman, Raynham, MA) and Thompson retractors (Thompson Surgical Instruments, Traverse City, MI).

After the laparotomy and general inspection, the liver is mobilized by transection of the obliterated umbilical vein and division of the falciform ligament, as it triangulates onto the IVC, to identify the origins of the hepatic veins and, in particular, the right middle groove and the left middle groove, if it is extrahepatic. Mobilization of the left and/or right lobes may be performed either before or after pedicular dissection. Left liver mobilization requires division of the left triangular ligament, and a laparotomy pad or sponge placed posterior to segment II can be valuable in protecting the cardia of the stomach and spleen, especially in a patient with a very long left lateral section that wraps over the spleen.

During the division of the lesser omentum (gastrohepatic ligament), attention should be given to the presence of an anomalous left hepatic artery, arising from the left gastric artery. Right liver mobilization requires division of the right triangular (“rookie”) ligament; division of the anterior layer of the coronary ligament, as it reflects from the diaphragm onto segment VIII; and the posterior layer of the coronary ligament that reflects onto segment VI. The liver is mobilized off the right hemidiaphragm, thereby exposing the bare area of segments VI and VII. The right adrenal gland is separated from segment VI (a densely adherent adrenal gland may be divided and oversewn), and the retrohepatic IVC is identified.

Intraoperative Assessment

Intraoperative assessment of the liver requires correlation of the findings of inspection and palpation of the mobilized liver with those of the preoperative imaging. Intraoperative US has been advocated to localize the lesion and further stage the proposed remnant liver (Makuuchi et al, 1991); however, with the increased precision of preoperative imaging, intraoperative ultrasound (IOUS) seldom alters the procedure (Jarnagin et al, 2001). IOUS of the liver may be valuable to identify venous tumor thrombus and to assess the proposed plane of transection and its relationship with major hepatic veins and portal triads.

Recently, systematic segmentectomy and subsegmentectomy by IOUS-guided finger compression has been described (Torzilli et al, 2010). This technique can be applied in each segment of liver, as long as the thickness of the parenchyma and the anatomy of liver are suitable. IOUS-guided finger compression of the vascular pedicle feeding the tumor at the level closest to it results in a demarcation area, allowing oncologic resection.

Transection Techniques

There are at least two distinct philosophies of liver transection, which result in distinct surgical techniques and surgical styles. The first is that blood loss from the transected liver is minimized by speed, external compression, vascular occlusion (outflow and/or inflow) (Bismuth et al, 1989; Stephen et al, 1996), and the use of surgical interventions to stop bleeding using cautery, sutures, and tissue glues. The second is that blood loss is best minimized by prevention of injury to vascular structures, using transection techniques that dissect out structures from the surrounding parenchyma as understood and anticipated by preoperative imaging and planning. Use of the Cavitron Ultrasonic Surgical Aspirator (CUSA; Valleylab, Boulder, CO), which reduces blood loss better than the clamp-crushing technique (Fan et al, 1996), has become the standard technique of liver transection even in cirrhotic liver (Takayama et al, 2001).

More recently, a third technique has been described that reflects a philosophy of prevention of bleeding that uses destructive hemostatic control of the parenchyma before transection (Ayav et al, 2007; Curro et al, 2008). We prefer the second approach, although clamp crushing, the conventional method of liver transection, is still used in some centers (Imamura et al, 2003; Jarnagin et al, 2002; Lin, 1974). Surgical techniques that facilitate a precise, controlled transection of liver parenchyma and allow the dissection of intrahepatic structures are the Helix Hydro-Jet dissector (ERBE USA, Marietta, GA) (Baer et al, 1991) and the CUSA dissector (Little & Hollands, 1991). Each provides selective destruction of liver parenchyma with relative sparing of denser fibrotic tissue, such as hepatic veins and portal triads. Inflow and outflow vascular occlusion may be added to these techniques for better hemostasis. Because no evidence clearly supports the superiority of any one technique (Clavien et al, 2003), the transection method for any particular operation should be dependent on local expertise.

Techniques that achieve destructive control of the parenchyma and any crossing structures before division include linear cutting staplers, in-line radiofrequency ablation (Habib; Angiodynamics, Latham, NY), and bipolar cautery (Gyrus, Gyrus ACMI, Southborough, MA; and LigaSure, Covidien, Boulder, CO). In-line radiofrequency ablation (RFA) allows surgeons to perform minor and major hepatectomies with minimal blood loss, low blood transfusion requirement, and reduced mortality and morbidity (Ayav et al, 2008); however, this device is seldom used in tertiary reference centers because of concerns about the preservation of venous drainage of the remnant liver and the risk of postoperative bile leak and necrosis (Kim et al, 2003; Lupo et al, 2007). The role of this technology is probably limited to segmental or wedge excision because of the potential risk of bile duct injury, when using this instrument near the liver hilum, and its inability to control bleeding from large venous branches.

Pretransection vascular control is used by many surgeons with oncologic, anatomic delimitation and hemostasis (Bismuth et al, 1989; Stephen et al, 1996). Early occlusion of the hepatic venous outflow of any resected segments may reduce the risk of venous tumor emboli. Occlusion of the hepatic artery (HA) and portal vein (PV) to those segments being resected facilitates the procedure by defining the line of division between ischemic segments to be removed and the well-perfused remnant liver for reduction of blood loss. Pretransection occlusion of the inflow of the segments to be resected before outflow results in better hemostasis. Occlusion of the inflow to sectors of the right hemiliver (VI and VII and V and VIII) or to the segments of the left lobe (II, III, IVa, and IVb) can be performed either by dissection and division of the artery and vein outside the liver, leaving the transection of the hepatic duct and remaining hilar plate for later in the procedure (Figueras et al, 2003), or by the glissonian technique (Launois & Jamieson, 1992), in which the sectoral or segmental pedicle is encircled, using either an anterior or posterior intrahepatic approach; this is done by incising the reflection of the Glisson capsule onto the portal structures to drop the hilar plate off the liver parenchyma, thereby encircling the pedicle. The duct, artery, and vein can be transected en masse either by suture or with a linear stapler.

Procedures

Monosegment and Bisegment Resections

Segment III or III Resection

Given the discrepancy between portal venous supply and biliary drainage, and also given the difficulty of preserving left hepatic venous drainage, the combined segment II and III resection (left lateral sectionectomy; Fig. 92.3) is safer and more feasible than isolated resection of segments II or III. When either of these segmentectomies is being planned, the plane of resection is by either side of the LHV (left and posterior for segment II resection, right and anterior for segment III). The inflow is approached on the left side of the falciform ligament by incising the peritoneal reflection onto the liver and identifying either the segment II or III portal pedicles. Once the inflow is divided, the line of parenchymal transection becomes prominent between the ischemic segment to be resected and the normally perfused residual segment.

FIGURE 92.3 Diagram of the planes of transection for resection of segments II and III or segments IV, V, VI, VII, VIII (extended right hepatectomy).

Combined Resection of Segments II and III: Left Lateral Sectionectomy

The left lateral section is mobilized by division of the falciform ligament and the left triangular ligament (Fig. 92.4). The extrahepatic portion of the left hepatic vein can be lengthened by dividing the fibrous tissue to the left of the IVC down to the level of the fissure for the ligamentum venosum, which is then ligated and divided as it enters the posterior aspect of the LHV; this allows encircling of this vein if the joining with the MHV is not intraparenchymal. Otherwise, the isolation of the LHV is delayed until completion of the parenchymal transection.

FIGURE 92.4 Diagram of the planes of transection for a right or left hepatectomy (hemihepatectomy).

The inflow to segments II and III is usually isolated during transection of the parenchyma to the left of the falciform ligament. Occasionally, pedicles to segments II and III could be identified and encircled outside the liver in the left side of the portoumbilical fissure. The plane of parenchymal transection follows the falciform ligament. As the liver is divided, the portal structures to segments II and III will become apparent, and these can be electively ligated and divided. Once this is done, and the parenchyma surrounding the LHV has been dissected, the vein can also be ligated and divided.

The transection is completed by dividing the parenchyma anterior to the caudate lobe, in the fissure for the ligamentum venosum. The blood supply to the caudate emerges from the PV and left HA at the level of the portoumbilical fissure, and these should be identified and preserved before the parenchymal transection.

Segment IV Resection

Isolated resection of segment IV or IVa alone is very uncommon. This segment is limited posteriorly by the hilar plate and IVC, on the right by the falciform ligament and the left PV, and on the left by the MHV. Inflow and biliary drainage to segment IV comes from left to right from the left-sided portal structures in the base of the falciform ligament (the “comeback” branches from the left portal vein). Sometimes, aberrant right anterior and posterior sectoral ducts cross in this position; these should be avoided during resection. Outflow from segment IV is predominantly to the MHV, but occasionally a separate draining vein (scissural vein) goes directly to the suprahepatic IVC or to the terminal part of the LHV or MHV.

Once the falciform ligament has been divided, with identification of the termination of the HVs, the arterial and venous inflow can be divided. By incising the peritoneal reflection on the right of the falciform ligament, the segment IVa and IVb pedicles can be isolated, encircled, and divided; the lines of transection become demarcated on the surface of the liver along the Cantlie line.

The resection continues at the base of segment IV off the anterior surface of the hilar plate. Care must be taken to avoid excessive use of cautery in the hilar plate, as the bile duct bifurcation and left hepatic duct lie immediately behind this area. Parenchymal transection commences on the right side of the falciform ligament with identification of portal pedicles to segments IVa and IVb. These may arise from a common trunk, and occasionally there are more than two, which is usually appreciable on preoperative imaging.

Transection continues superiorly to the level of the suprahepatic IVC to the junction of the LHV and MHV. The LHV and MHV commonly join within the liver at this point prior to insertion into the IVC, and in this case, the dissection terminates inferior to this point. Care should be taken to identify significant venous tributaries from segment IV into the left hepatic vein, which may not be appreciated on preoperative imaging. The dissection of the right side is along the Cantlie line to the left of the MHV. Several tributaries to the middle hepatic vein, the IVa and IVb veins, will need to be identified and ligated. Once the medial border of the hilar dissection has been reached, the parenchymal transection is done in a transverse plane to complete the separation of segment IV.

Segment V or VIII Resection

These two segments compose the right anterior sector. The bifurcation of the right portal pedicle into anterior and posterior pedicles is intrahepatic, and primary ligation of these pedicles is difficult, especially for segment VIII; therefore some parenchymal transection along the Cantlie line toward the pedicle is required before its division to allow demarcation of either segment V or VIII. The segment V pedicle emerges anteriorly and runs anteroinferiorly, and the segment VIII pedicle emerges posteriorly and runs superiorly. The horizontal plane of transection for an isolated segment V or VIII resection runs through the liver at the level of the bifurcation of the portal vein, with segment V below and segment VIII above this line. The medial and lateral limits of the resection are the middle and right hepatic veins, respectively.

Segment V Resection

Isolated segment V resection begins with division of the liver on the undersurface up the center of the gallbladder fossa and anteriorly along the Cantlie line halfway up toward the IVC. Then the parenchyma is divided in a plane to the left of the RHV, which extends on the undersurface of the liver along the incisura dextra to the free edge and anteriorly halfway toward the IVC. This posterior plane is quite coronal and usually results in a large exposed area of parenchyma. The resection is completed by connecting the two vertical transection lines by division of the parenchyma horizontally from anterior to posterior immediately below the level of division of the portal vein.

Segment VIII Resection

Isolated segment VIII resection is a very challenging procedure, because no external demarcation of this segment is apparent. The initial landmark is the Cantlie line with a parenchymal transection in the right side of the MHV. The segment VIII pedicle, which corresponds to the ascending division of the right anterior sectoral pedicle, can be isolated either at this point, after division of the liver, or by dividing the liver between segments IV and V in the horizontal plane along the level of the portal bifurcation. This latter maneuver is useful, as it allows for demarcation of the right-sided resection margin, which is on the left side of the RHV. This horizontal transection should follow the coronal plane of the RHV, which requires IOUS guidance.

The parenchymal division of the right-sided resection margin continues superiorly; using the termination of the RHV as a landmark, there is often only 1 to 2 cm of liver at the upper margin of the transection between the RHV and MHV. Care must be taken during the right-sided parenchymal division to adhere to the correct transection plane, as this plane takes about a 45-degree angle from the vertical. This allows resection of all the liver in segment VIII, while avoiding injury to the RHV. The segment VIII resection is completed by separating the remaining parenchyma off the deep attachment to the IVC, although this should have been mostly completed during mobilization.

Combined Resection of Segments V and VIII

The combined resection of segments V and VIII requires the division of the right anterior sectoral portal triad with left-sided parenchymal division along the Cantlie line along the right side of the MHV; the right-sided parenchymal division is in the coronal plane of the left side of the RHV. The anterior sectoral pedicle may be encircled from outside the liver, either anteriorly or posteriorly, and it is divided en masse with a linear cutting stapler, or it may be identified during the parenchymal transection along the Cantlie line at the base. Early division of the inflow provides demarcation of the ischemic parenchyma, which facilitates identification of the planes of parenchymal transection.

Segment VI or VII Resection

The right posterior sectoral pedicle can be identified in the incisura dextra of Ganz, which corresponds to the horizontal fissure lateral to the gallbladder fossa. The segment VI/VII branch of the right HA can usually be isolated extraparenchymally; however, the segment VI/VII portal branch, which corresponds to the posterior division of the right portal branch, is more difficult to isolate. Therefore the pedicle for an isolated resection of segment VI or VII is usually approached within the liver during parenchymal transection (Fig. 92.5). A resection of segment VI or VII requires complete mobilization of the right lobe of the liver with division of the segment VI and VII hepatic veins, when present, to the IVC.

FIGURE 92.5 Diagram of the planes of transection for resection of segments VI and VII or segments II, III, IV, V, and VIII (extended left hepatectomy).

Segment VI Resection

Isolated segment VI resection (Figs. 92.5 and 92.6) commences with an oblique transection line along the incisura dextra in the inferior surface of the liver and anteriorly halfway toward the IVC, following the posterior side of the RHV. The horizontal plane of resection is at the level of the PV bifurcation. The descending branches of the right posterior sectoral portal triad are encountered about two thirds of the way through the dissection. The resection is completed by taking a horizontal transection plane through the posterior surface of the liver lateral to the right hepatic vein.

FIGURE 92.6 Diagram of the planes of transection for resection of segments V and VI.

Segment VII Resection

An isolated segment VII resection (see Fig. 92.5) commences with the horizontal transection line just above the bifurcation of the portal vein; this line is congruous with the horizontal resection line for a segment VI resection. The resection continues medially to the lateral margin of the RHV. During the horizontal resection, the ascending right posterior sectoral branches can be isolated and divided, which will allow for demarcation of the medial aspect of the resection. The vertical transection line runs obliquely through the liver lateral and posterior to the RHV.

Combined Resection of Segments VI and VII

This right posterior sectorectomy (see Fig. 92.5) is a procedure often considered as an alternative to a right hepatectomy, especially in patients with diseased parenchyma. Identification of the right posterior sectoral pedicle may be possible from outside the liver. Early division of the inflow facilitates the identification of the transection margins. Otherwise, the segment VI and VII HA and PV may be divided separately, leaving the transection of the VI and VII duct and plate for later, during the parenchymal transection. The plane of transection posterior to the RHV is coronal and results in a relatively large surface area of cut parenchyma, which requires specific attention for hemostasis and biliostasis.

Combined Resection of Segments V and VI

Resection of these two segments is very commonly performed. The vertical plane of transection is along the Cantlie line on the right side of the MHV from the edge of the liver to halfway up toward the IVC (see Fig. 92.6). The horizontal plane of transection is at the level of the PV. The portal pedicles to segments V and VI are usually divided during the parenchymal transection, which requires full mobilization of the right lobe of the liver from the diaphragm with division of segment VI and most, if not all, of the segment VII hepatic veins on the anterior surface of the IVC. The transection starts in the middle of the gallbladder fossa and extends along the Cantlie line up to the level of the right portal pedicle. Then with a dissection to the left, the horizontal plane of transection is developed from the top of the vertical plane. The segment V portal pedicle may be identified at the base and divided, followed by division of the segment VI pedicle posteriorly. From right to left, the horizontal dissection plane reaches the RHV.

Three or More Segmental Resections

Resection of Segments V Through VIII: Right Hepatectomy

Right hepatectomy is a very well-standardized procedure, consisting of resection of liver parenchyma on the right side of the Cantlie line in the right side of the MHV (see Fig. 92.4). The inclusion of the MHV corresponds to an extended right hepatectomy. Inflow and outflow control prior to transection may be appropriate and can be accomplished in many ways, and parenchymal resection can be performed with or without an intermittent Pringle maneuver. Mobilization commences by dividing the falciform ligament as it triangulates onto the IVC. The right middle groove, between the right hepatic and middle hepatic veins, is developed taking care not to injure a small tributary that may empty directly into the IVC from segment VIII.

Dissection of the porta hepatis commences with a cholecystectomy. A glissonian approach to the right portal pedicle may be performed by dividing the capsule that reflects onto the porta anteriorly and posteriorly, hugging the sheath as it is dropped off the parenchyma. Once encircled, the pedicle may be divided en masse with an Endo GIA (Covidien) stapler. Alternately, the inflow HA and PV may be dissected and divided individually. The peritoneum posterior and lateral to the portal structures is incised, and the RHA or its branches can be identified and divided. The peritoneum along the PV is incised, and the PV is mobilized off the back of the bile duct to clearly identify the bifurcation and origin of the left PV. The dissection continues cephalad along the anterior surface of the right PV. A small branch off the posterolateral aspect of the right PV to segment VI should be identified and divided to provide sufficient length for transection. The right PV is then encircled, taking care to divide any small branches that arise from the bifurcation, and it is divided with a vascular stapler. The liver should demarcate along the Cantlie line.

The right liver is mobilized by dividing the coronary ligament then exposing the bare area of the liver by dissecting the diaphragm and adrenal off the liver to expose the IVC. Rotation of the liver along the axis of the IVC facilitates this dissection. Division of the left triangular ligament may make this rotation easier, especially when the liver is large, or when the patient is obese. Once the IVC has been identified, the segment VI and VII hepatic veins are ligated and divided. The retrocaval fibrous bridge between segments VII and I is divided, taking care to control any significant veins that may run through it. The RHV identified is encircled by passing a Kelly hemostat up the right middle groove between it and the MHV. The RHV is then divided with a vascular stapler, and an umbilical tape is placed in the groove of the IVC behind the liver to perform the hanging maneuver.

The parenchymal transection commences at the gallbladder fossa along the line of demarcation. The first major structure to be expected is the segment V hepatic vein, as it becomes the MHV. After division of this vein, the parenchymal transection continues along a broad front, either staying to the right side of the MHV or leaving a small amount of liver parenchyma on the surface of the vein. The hilar plate containing the right hepatic duct is approached at the base of the resection plane and may be divided prior to completion of the superior aspect of the parenchymal transection. Division of the bile duct and the hilar plate allows the parenchyma of the superior aspect of the liver to be separated and consequently reduces the risk of hepatic vein injury. Uppermost parenchymal transection is facilitated by placing some upward traction on the umbilical tape, the so-called hanging maneuver, dividing any segment VIII veins that cross over to the MHV. The dissection is completed posteriorly by dividing the glissonian capsule in the caval groove.

The right hepatectomy can be extended to include the middle hepatic vein and part of segment IV. To include the MHV, the transection begins to the left of the gallbladder fossa, and the first major structure expected is the segment IVb vein as it forms the MHV. Transection is then carried out to the left of the MHV, dividing any IVa veins that cross over to it. The MHV is encircled and divided before its junction with the LHV. Alternatively, the MHV may be identified and divided outside the liver, early after division of the RHV, by mobilizing a part of the caudate lobe off the IVC and encircling the MHV. In order to include segment IV in the resection specimen, the plane of transection is 1 cm to the right of the falciform ligament. The recurrent branches of the left portal triad to segments IVa and IVb need to be divided within the liver.

Resection of Segments II to IV: Left Hepatectomy

A left hepatectomy consists of resection of segments II, III, IVa, and IVb along the the Cantlie line to the left of the MHV (see Fig. 92.4). An extended left hepatectomy includes the MHV and/or segment I (caudate lobe). Inflow and outflow control prior to transection may be appropriate and can be accomplished in many ways, and parenchymal resection can be performed with or without an intermittent Pringle maneuver. Mobilization commences by dividing the falciform ligament as it triangulates onto the IVC. The plane between the LHV and MHV may be developed anterior to the IVC; however, the LHV and MHVs may join within the substance of the liver, and the left vein may not be able to be encircled outside the liver. To encircle the LHV, the ligamentum venosum is divided within its fissure to allow access to the posterior aspect of the LHV. Alternatively, the LHV may be divided at the end of the parenchymal transection, and control of vascular inflow may be appropriate. Using the glissonian approach, the left portal pedicle is encircled, and the pedicle may be transected en masse using an Endo GIA stapler. Alternatively, the branches of the left HA and the left PV may be divided outside the liver, leaving the left hepatic duct and plate to be divided late during the parenchymal transection.

The base of segment IV is dissected off the anterior surface of the bile duct bifurcation to allow for the transection line to be defined. The branches of the left HA are identified on the left side of the porta hepatis and are ligated. An early segment IV branch is often present, and this also should be ligated. The anterior surface of the PV can be identified and mobilized to clearly identify the origin of the right PV, and the left PV is encircled after dividing one or two of the branches to the caudate lobe. The left PV can then be ligated and divided. The parenchymal transection commences along the Cantlie line beginning to the left of the gallbladder fossa. The first major vascular structure encountered is the segment IVa vein, as it becomes the MHV. When the MHV is identified, the dissection is carried in a cephalad direction on its left side.

At the base of segment IV, the parenchymal transection should be carried to the left to minimize injury to any aberrant right hepatic ducts draining into the left hepatic duct. If the plane of transection is close to the falciform ligament, leaving the medial portion of segments IVa and IVb, the segment IVa and IVb portal pedicles that return from the left portal structures are identified and divided. The hilar plate is transected using a stapler, or it is ligated and divided. As the parenchymal transection continues cephalad, the LHV will become apparent, and it should be divided proximal to its junction with the MHV, if it was not divided outside the liver. The resection is completed by separating the parenchyma of segments II and III off the caudate lobe, ending by dividing the capsule along the caudate groove.

The left hepatectomy can be extended to include the MHV and variable amounts of segments V and VIII. Left hepatectomy extended to the right parenchyma with part or all of segments V and VIII could include parenchymal transection up to the left side of the RHV. In this procedure, also called anterior hepatectomy, the plane of transection is almost parallel to the operating table. The right anterior sectoral pedicle is usually ligated within the liver during the parenchymal transection. The right anterior and posterior pedicles can be orientated in many different ways, and it is important to ensure that the correct pedicle has been isolated, before anything irreversible has been done. This can be achieved by temporary pedicle clamping with a bulldog vascular clamp, assessing the delimitation of devascularized parenchyma. The anterior surface of the RHV should be cautiously dissected.

These major resections can be combined with caudate lobe and extrahepatic biliary tree resection in some cases of hilar cholangiocarcinoma. En bloc resection requires prior mobilization of the caudate off the IVC.