Complete Caudate Lobectomy: Its Definition, Indications, and Surgical Approaches

There are three ways to approach and resect the caudate lobe of the liver, that is; and isolated caudate lobectomy, a combined resection of the liver overlying the caudate lobe, and a transhepatic anterior approach by splitting parenchyma of the liver. We had two patients with neoplasms originating in the caudate lobe who underwent a complete caudate lobectomy. Both patients have been doing well without liver dysfunction. Although after the transhepatic anterior approach we anticipated an adverse effect from splitting the parenchyma of the liver, the postoperative course was uneventful and similar to that of the right side approach.


INTRODUCTION
Although it has beert demonstrated that various hepatic resections was carried out safely [1,2], the caudate lobectomy is still a challenging problem because of its anatomical complexity [3].
The caudate lobe is easily invaded by cancer of the hilar bile ducts, so that the necessity of Surgical Anatomy The caudate lobe consists of the spigelian lobe (the left lobe, or segment I in Couinaud's classification), the paracaval portion (the right lobe, or segment IX in Couinaud's classification [6]) and the caudate process (Fig. 1). The caudate lobe has some variations of its vascular structure [3,7]. The arterial branches arise from the left *Address for reprint requests: Akinori Sasada, MD, Department of Surgery Division II, Kobe University School of Medicine, 7-5-2, Kusunoki-cho, Chuo-Ku, Kobe, 650, Japan. caval portion of the caudate lobe with or without imparied liver function.

Patients and Methods
During the last last five years, we have operated on two patients with neoplasms originating in the caudate lobe, one large hemangioma and one metastatic liver carcinoma from a rectal carcinoma.
The preoperative liver function was within normal limits in each patient, and the hepatic parenchyma in each patient was also macroscopically normal without chromic degenerative changes.
The complete caudate lobectomy for these two patients is summarized in Table I. Transphepatic anterior approach was chosen in a 36 year-old female patient complaining of continuous back pain with a large hemangioma in the caudate lobe (Fig. 2a) because the parent was young and their would be minimal loss of the remaining liver.
The laparotomy was performed through a Jshaped abdominothoracic incision with a diaphragmatic transection.
On inspection, the left portion of the spigelian lobe remained normal. The intraoperative ultra-  Thereafter the hepatic parenchyma was split in two directions; on the left side toward the resected ligamentum venosum and on the right side just behind the MHV. In order to identify the boundary between the right hepatic lobe and the right border of the paracaval portion and caudate process, 15 ml of indigotindisulfonate sodium solution was injected into the right posterior branch of the PV. The right border of the caudate lobe was thereby kept unstained and was marked along the unstained margin with an electrocautery. The complete caudate lobectomy was performed en bloc from caudally to cranially. The bleeding from the liver raw surface continued until complete removal of the hemangioma occupying the paracaval portion, because its cranial extremity was situated at the confluence of the RHV and MHV into the IVC. The operation time was 11 hours 40 minutes, and intraoperative blood transfusion was required for the blood loss of 5,600 ml. The removed hemangioma was 7.0 x 5.0 x 3.0 cm in size and histology revealed cavernous hemangioma.
Right side approach was used in a 50year-old male patient who underwent Miles' operation for rectal carcinoma three years previously, and was recently found to have metastatic lesions in the caudate lobe and segment $6 ( Fig. 3a).
A thoracoabdominal incision through the right seventh intercostal space was made. The diaphragm was diagonally transected towards the IVC.
Intraoperative ultrasonography of the whole liver revealed no other metastatic lesion. Therefore, we decided to carry out the complete caudate lobectomy concomitant with the right posterior segmentectomy by means of a right side approach.
After complete mobilization of both hepatic lobes from the abdominal wall and the diaphragm, the gallbladder was removed to expose the hepatic hilum. The mobilized lateral segment was lifted ventrally to separate the ligamentum venosum. Since the fissure for the ligamentum venosum was completely separated, the left border of the spigelian lobe was freed from the IVC. The common hepatic duct (CHD) was separated and encircled with a tape. By retracting the tape around the CHD to the left and upward, the right hepatic artery behind the CHD was encircled with a tape. The surrounding connective tissue along the right hepatic artery was dissected until its division into the anterior and posterior branches. Subsequently the right portal vein (RPV) was separated to be encircled with a tape, and was dissected along the RPV up to its bifurcation into the anterior and posterior branches. Each branch of the RPV was encircled with a tape, respectively. The vessels to the left lobe of the liver were also separated to be encircled with a tape as in the right lobe. The hilar separation of arterial and portal branches to the caudate lobe was performed. The SHVs were completely ligated and dissected from both sides of the IVC.
Next the right posterior branches of the hepatic artery and portal vein were ligated, the demarcated area appeared on the surface of the liver. We confirmed the RHV by ultrasonography, a follow-up magnetic resonance imaging (MRI) transection line on the liver, at the discolored after 6months of the operation in Patient 2 border, was marked on the surface of the liver showed the small cavity around the IVC with an electrocautery, substituting the resected caudate lobe. The A hemihepatic vascular occlusion (clamping remnant liver was well hypertrophied. No for 30minutes and declamping for 10minutes) recurrent lesions were detected on the MRI was applied to control the blood supply to the (Fig. 3b). right remnant lobe of the liver. The transection Both patients have been doing well without along the intersegmental plane of the right lobe liver dysfunction nor recurrence after 3 years was continued toward the freed ligamentum and I year respectively, after complete caudate venosum. Half way through the transection, lobectomy. each posterior segmental branch of the hepatic artery, portal vein and bile duct was ligated doubly and dissected at the hepatic hilum.

DISCUSSION
As the posterior segment of the liver was retracted lateral-ventrally, the complete caudate A neoplasm originating in the caudate lobe is lobectomy together with a right posterior seg-very rate [16], so that an isolated complete mentectomy of the liver was performed as en bloc.
The operation time was 7hours 30minutes, but no blood transfusion was needed. The

POSTOPERATIVE COURSE
The postoperative courses were uneventful in both patients without any signs of liver failure. The postoperative peak levels of total bilirubin were 35.7 lamol/1 a.nd 34 tmol/1 on the first postoperative day, respectively, and then gradually returned to normal values. The anticipated adverse effect from splitting the liver parenchyma was hardly recognized in Patient 1.
Postoperative computed tomography after one month in Patient 1 demonstrated the cavity around the IVC and the free space along the split line of the liver parenchyma (Fig. 2b). The resection of the caudate lobe still remains transfusion for 5,600 ml of blood loss. However, unfamiliar to many surgeons, the postoperative liver function was smoothly Our cases were one hemangioma, and one restored to normal range in a few days without metastatic tumor from rectal carcinoma and the harmful effects from splitting the liver parenchcomplete caudate lobectomy was successfully yma in half. performed through the transhepatic anterior In spite of the demerits described above, the approach and the right side approach combined transhepatic anterior approach, providing an with a posterior segmentectomy, respectively, excellent surgical view, is safe and gives good When a tumor is too large and mainly located access to perform a complete resection of the in the paracaval portion of the liver, the caudate lobe [14,15]. This approach also transhepatic anterior approach is generally used preserves the remnant liver function well as in to perform the precise surgery [15], although our patient. this surgical procedure is more complex than The right side approach for the caudate other approaches, lobectomy is carried out to simplify the proce-The right border of the paracaval portion, dure [8,13] or to omit dissection of the unclear which lies in front and to the right of the IVC, is right caudal border. The hepatic transection in continuity with the right lobe of the liver, through the intersegmental plane along dorsal Furthermore, between the IVC and the right aspect of the RHV using hemihepatic vascular portal pedicle, the caudate lobe is united with occlusion was simpler anatomically and technithe right posterior segment of the liver by the cally than a transhepatic anterior approach. caudate process. As it is hard to recognize the Therefore, this procedure had a shorter operatlandmark indicating the boundary of the cauing time and less blood loss. However, a date lobe and the right lobe of liver, we used to preparatory or combined resection of the hepatic counterstainingmethod [17] with injection of the segment or lobe overlying the caudate lobe dye into the posterior branch of the PV. The could trigger off postoperative hepatic failure paracaval portion receives a blood supply from even in the normal liver [1,15]. All the more for many tiny vessels other than the posterior the patient with impaired liver function, a segmental branch [6]. Therefore, a counterstain-combined resection and sacrifice of hepatic ing the posterior segment of the liver is parenchyma could easily cause fatal hepatic impractical but useful clinically [15,17]. failure.
In comparison with conventional procedures, Recently some authors [10][11][12] described the transphepatic anterior approach has some novel procedures about an isolated caudate disadvantages of longer operative duration, lobectomy. However, their procedures would more blood loss and harmful effects by splitting be still critical and risky because of the anatoparenchyma of the liver. We thought that the mical complexity and a poor opportunity for resection through the caudal approach would be surgical manipulation in the limited space more dangerous in this case, because this behind the main liver lobes. Therefore, an ex approach gives a very narrow surgical field, situ operation has been occasionally recomand moreover, the hemangioma in Patient 1 mended instead of these difficult procedures occupied mainly the paracaval portion and [8,18]. caudate process, its cranial extremity reached We performed the transhepatic anterior apthe confluence of the RHV and MHV into the proach and the right side approach for the IVC. Indeed, and intraoperative hemorrhage complete caudate lobectomy in two patients. continued until complete removal of the tumor, Both approaches had excellent results without requiring intraoperatively 3,000ml of blood any troubles. Finally, we would emphasize that surgeons must give a serious consideration on a patient by patient basis including the occupied region of tumor, the remnant liver reserve, and the vascular structure surrounding tumor in order to determine the best approach to the caudate lobe. Masson., p. 127.

Re[erences
[17] Takayama, T., Makuuchi Dr Sasada and his associates are to be congratulated for publishing two complete caudate lobectomies using respectively a transhepatic anterior approach and a right side approach. This succcessful result is the result of an excellent knowledge of the segmental anatomy of the liver an an impressive mastering of liver resection. This paper contains one of the best illustration of the anatomy of the caudate lobe ever published. A good knowledge of this hidden part of the liver which is of extreme importance in liver surgery because it can be involved by tumours. The so-called dorsal sector by Couinaud consists of segment I, or the caudate lobe, and segment IX, also named the right paracaval region [1]. This dorsal sector is situated between the IVC and the large (right, middle and left) hepatic veins and the liver hilum. Japanese authors refer to this entire part simply as the caudate lobe and divide it into a left part, or Spiegel's lobe, and a right part [2]. A surgeon should know that he can see and palpate only the left part of this dorsal sector, but a large part of this region of the liver is hidden. Dr Sasadas' description of the access of the right part of the dorsal sector through a transhepatic anterior approach in one case and after complete mobilisation of the right liver should be noticed. According to our experience, further studies should determine the indication of primary resection of the left lateral segment (segment I and II) in order to facilitate the access to the dorsal sector. As experienced by the authors the situation of the dorsal sector between the IVC and the large hepatic veins may cause major bleeding. In this indication we advocate total vascular occlusion of the liver [3].
Although we dramatically restrict our indications of ex-situ procedure, we think that this method should be considered in such cases [4].
COMMENTARY ON MANUSCRIPT COMPLETE CAUDATE LOBECTOMY: ITS DEFINITION, INDICATIONS, AND SURGICAL APPROACHES This paper describes two different approaches for complete caudate lobectomy and the experience gained when using the anterior, transhepatic and the right-sided approaches. Complete caudate lobectomy is uncommon and can be technically demanding. The present paper adds to existing experience [1][2][3][4][5][6][7].
The caudate lobe may be excised with a posterior (caudal, dorsal) approach or an anterior, transhepatic approach. It appears that a posterior approach is advisable in most patients, and that a transhepatic approach may be reserved for large tumours and especially for cirrhotic livers. Bleeding from hepatic veins is the main concern during caudate lobectomy, and this may be difficult to avoid or control unless the liver, including the caudate lobe, can be fully mobilized. It may be impossible to safely obtain full mobilization and control with the posterior approach if the tumour is large and firm and especially if the liver is rigid from cirrhosis. A transhepatic approach may therefore be recommended in these situations. In some patients with liver cirrhosis it is, however, possible to perform a safe posterior resection if the hepatic veins can be controlled extrahepatically [5][6][7]. Extrahepatic control of the hepatic veins is advisable also in patients without cirrhosis if the tumour is large and/or is close to the entrance of the (right), middle and left hepatic veins into the vena cava and may be combined with the transhepatic approach. I have no experience with the transhepatic approach, but I guess that I would have enucleated the haemangioma (patient no. 1) using a posterior approach and control of hepatic veins.
Surgical strategy should of course be tailored to the circumstances. Among other things, this also means that the posterior approach can be righ-sided or left-sided or alternate between the two sides, as emphasized by Bartlett et al. [7].
The rule is to operate where it is as "easy" as possible.
The fact that isolated caudate lobectomy is technically feasible does not mean that it should be used in all patients with malignant tumour in the caudate lobe. As emphasized by Elias et al. [2], there is risk for inadequate tumor clearance for anatomical reasons. Thus, in a patient with adequate hepatic reserve one should not hesitate to remove more segments en bloc with the caudate lobe to ensure free resection margins.