Configuration of the right portion of the caudate lobe with special reference to identification of its right margin

A comprehensive study and extensive review of the Caudate lobe: The last piece of "Jigsaw" puzzle

Many liver surgeons have updated their understanding of the liver in recent years because of detailed studies on the liver anatomy and the rapid advances in laparoscopic liver surgery. Despite newer approaches, concepts and methods, research on the caudate lobe continues to be based on case reports and several persistent challenges concerning caudate lobe surgery that are worth discussing. Based on the literature and the author's experience, this study considers and addresses the challenges associated with caudate lobectomy encountered by most liver surgeons. We searched PubMed for relevant articles in English for 'caudate lobe', 'cholangiocellular carcinoma', 'laparoscopic caudate resection', 'right-side boundary of the caudate lobe' and 'assessment of hepatic functional reserve' published up to May 2022. This study reviewed the anatomical history of the caudate lobe, focusing on the challenges associated with caudate lobe-related surgical resection. Due to the unique anatomical position of the caudate lobe, surgical strategy for caudate lobe resection is particularly important, and the technical requirements for hepatobiliary surgeons are also extremely strict. Therefore, understanding the anatomical history of the caudate lobe and discussing the challenges associated with caudate lobectomy is essential.

Isolated caudate lobectomy using a modified hanging maneuver

BACKGROUND

The caudate lobe is located deep in the dorsal portion of the liver. Complete resection is an extremely demanding surgery due to the limited surgical field, especially in cases with severe intra-abdominal complications. A major concern of isolated caudate lobectomy is the difficulty associated with securing the contralateral visual field during parenchymal transection. To overcome this issue, we present a new technique for isolated caudate lobectomy that uses a modified hanging maneuver.

METHODS

We performed an anatomical isolated caudate lobectomy via the high dorsal resection technique using our new modified hanging maneuver in two patients with HCC in November and December 2019.

RESULTS

Patient 1 was severely obese, so the upper abdominal cavity was occupied by a large amount of great omental fat, and fibrous adhesions were observed around the spleen. Patient 2 had undergone six preoperative treatments, and a high degree of adhesion was observed in the abdominal cavity around the liver. It was difficult to secure the surgical field due to severe abdominal complications in both cases. The total operation times in these two cases were 617 and 763 min, respectively, while the liver parenchymal dissection times of the caudate lobe were 96 and 108 min, respectively. The resection margin was negative in both patients (R0). Neither patient had any complications after surgery; both were discharged on postoperative day 14.

CONCLUSION

Our modified hanging maneuver is useful, particularly in cases with a narrow surgical field due to severe adhesions, bulky tumors, and/or hypertrophy of the Spiegel lobe.

Robotic isolated partial and complete hepatic caudate lobectomy: A single institution experience

BACKGROUND

Current reports on robotic hepatic caudate lobectomy are limited to Spiegel lobectomy. This study aimed to compare the safety and feasibility of robotic isolated partial and complete hepatic caudate lobectomy.

METHODS

Clinical data of 32 patients who underwent robotic resection of the hepatic caudate lobe in our department from May 2016 to January 2020 were retrospectively analyzed. The patients were divided into three groups according to the lobectomy location: left dorsal segment lobectomy (Spiegel lobectomy), right dorsal segment lobectomy (caudate process or paracaval portion lobectomy), and complete caudate lobectomy. General information and perioperative results of the three groups were compared and analyzed.

RESULTS

Among the 32 patients, none had conversion to laparotomy, three received intraoperative blood transfusion (9.38%), and none had complications of Clavien-Dindo grade III or higher or died in the perioperative period. Among them, 17 patients (53.13%) underwent Spiegel lobectomy, 7 (21.88%) underwent caudate process or paracaval portion lobectomy, and 8 (25.00%) underwent complete caudate lobectomy. The operative time and blood loss in the left dorsal segment lobectomy group were significantly better than those in the right dorsal segment lobectomy and complete caudate lobectomy groups (operative time: P = 0.010 and P = 0.005; blood loss: P = 0.005 and P = 0.017, respectively). The postoperative hospital stay in the left dorsal segment lobectomy group was significantly shorter than that in the complete caudate lobectomy group (P = 0.003); however, there was no difference in the postoperative hospital stay between the left dorsal segment lobectomy group and right dorsal segment lobectomy group (P = 0.240).

CONCLUSIONS

Robotic isolated partial and complete caudate lobectomy is safe and feasible. Spiegel lobectomy is relatively straightforward and suitable for beginners.

Robotic anatomic isolated complete caudate lobectomy: Left-side approach and techniques

BACKGROUND

To demonstrate the surgical procedures and techniques of the robotic anatomical isolated complete caudate lobectomy.

METHODS

A retrospective analysis was performed on the demographic, operative, postoperative outcomes of seven patients who underwent robotic anatomical isolated complete caudate lobectomy at our department from January 2018 to November 2019. Mobilization of the left lateral and Spiegel lobe, dissection of the short hepatic veins and liver parenchyma transection from the dorsal plane of middle and right hepatic vein were crucial procedures for the robotic left-side approach. Anatomic complete caudate lobectomy was defined as total removal of the caudate lobe, in which the dorsal middle and right hepatic vein, the inferior vena cava and its right side were fully exposed on the raw surface.

RESULTS

All patients successfully underwent the robotic anatomical isolated caudate lobectomy with a left-side approach without conversion to laparotomy, and without Clavien-Dindo Grade III or higher complications. The average tumor diameter was 65.00 ± 10.61 mm, the average operation time was 212.00 ± 74.53 min, the median bleeding loss was 100 mL, and the average postoperative hospital stay was 8.71 ± 4.89 d, respectively. There were four patients with primary hepatocellular carcinoma, one with tumor recurrence five months after surgery and three patients were free of recurrence. All patients survived at the last follow-up.

CONCLUSION

Robotic anatomical isolated complete caudate lobectomy with a left-sided approach is safe and feasible for selected patients.

Can we delineate preoperatively the right and ventral margins of caudate lobe of the liver?

Purpose

Complete removal of the caudate lobe, which is sometimes necessary, is accomplished via isolated caudate lobectomy or hepatectomy that includes the caudate lobe. It is impossible, however, to confirm the right and ventral margins of the caudate lobe by preoperative imaging. This study was undertaken to determine whether we could identify the right and ventral margins of the caudate lobe preoperatively using Synapse 3D visualization software.

Methods

Ninety-four preoperative 3-dimensional (3D) computed tomographic images (1-mm slices) of the liver from candidate donors were examined. The images of the caudate lobe were subjected to a counter-staining method according to Synapse 3D to delineate their dimensions. We first examined whether the right margin of the caudate lobe exceeded the plane formed by the root of the right hepatic vein (RHV) and the right side of the inferior vena cava (IVC). Second, we determined whether the ventral margin of the caudate lobe exceeded the plane formed by the root of the middle hepatic vein (MHV) and the root of the RHV.

Results

For the right margin, 17 cases (18%) exceeded the RHV-IVC plane by a mean of 10.2 mm (range, 2.4–27.2 mm). For the ventral margin, 28 cases (30%) exceeded the MHV-RHV plane by a mean of 17.4 mm (range, 1.2–49.1 mm).

Conclusion

Evaluating the anatomy of caudate lobe using Synapse 3D preoperatively could be helpful for more precise anatomical resection of the caudate lobe.

Anatomical Boundary Between the Caudate Lobe of the Liver and Adjacent Segments Based on Three-Dimensional Analysis for Precise Resections

BACKGROUND

Right hemihepatectomy or systematic resection of segment 7 or 8 involves partial resection of the paracaval portion of the caudate lobe. However, the boundary between the caudate lobe and segment 7 or 8 remains unclear. We examined the anatomical territory of the caudate lobe with special reference to the boundary between the paracaval portion and segment 7 or 8 for precise anatomical hepatectomies.

METHODS

We enrolled 63 consecutive healthy donor candidates for living-donor liver transplantation from 2012 to 2014 in this study. The caudate lobe was defined according to Kumon's subdivision system, and the boundary between the paracaval portion and segment 7 or 8 was investigated based on three-dimensional computed tomography scan images using SYNAPSE VINCENT^®.

RESULTS

The paracaval portion of the liver protruded on the liver surface underneath the right diaphragm on the ventral side of the right hepatic vein (RHV) in 10 participants (16%) and on the dorsal side of the RHV in 9 participants (14%). A branch of the RHV, the "paracaval vein," was found in all 63 participants and ran longitudinally along the right border of the paracaval portion (n = 30, 48%) and within segment 7 (n = 16, 25%) or segment 8 (n = 17, 27%).

CONCLUSIONS

The paracaval portion of the liver protruded on the liver surface underneath the right diaphragm in one third of our participants. The paracaval vein can be a landmark for the boundary between the caudate lobe and the segment 7 or 8 in half of the cases.

Fetal intrahepatic gallbladder and topographical anatomy of the liver hilar region and hepatocystic triangle

The fetal gallbladder (GB) is embedded in a deep fossa surrounded by the liver parenchyma. Using 15 specimens with intrahepatic GB (crown-rump length 45-92 mm; approximately 9-13 weeks of gestation), we assessed the fetal topographical anatomy of the hepatocystic triangle and the porta hepatis. The cystic duct displayed a long upward course (0.9-4.5 mm along the supero-inferior axis) from the GB, along the duodenum, to the common bile duct in the hepatoduodenal ligament, via an independent mesentery separated from liver parenchyma by a recess of the peritoneal cavity. Notably, the course varied in length among specimens, not among stages. At the porta hepatis, we were able to distinguish the supraportal course of the posterior right hepatic duct overriding a portal vein branch to segment 8 (6/15) from the other, infraportal course (9/15). In the latter type, the portal vein bifurcation was superior to the cystic duct course. Two margins of the hepatocyctic triangle were very long in fetuses because of the inferiorly located intrahepatic GB. Thus, the triangle seems to be difficult to identify in prenatal ultrasound. During changes in location after 9 weeks, the GB fundus remains attached to the liver because the cystic artery was often embedded in the liver parenchyma. A failure in the embedding and re-exposure process of the GB may result in anomalous peritoneal folds around the GB.

Topographical anatomy of Spiegel's lobe and its adjacent organs in mid-term fetuses: Its implication on the development of the lesser sac and adult morphology of the upper abdomen

At 8-16 weeks of gestation, Spiegel's lobe of the caudate lobe appears as a sac-like herniation of the liver parenchyma between the inferior vena cava and ductus venosus or Arantius' duct. In 5 of 11 fetuses at 20-30 weeks of gestation, we found that an external notch was formed into the posterior aspect of the caudate lobe by a peritoneal fold containing the left gastric artery. This notch appeared to correspond to that observed in adults, which is usually seen at the antero-inferior margin of the lobe after rotation of the lobe along the horizontal or transverse axis. However, the notch did not accompany two of the three fetuses in which the left hepatic artery originated from the left gastric artery. Notably, until 9-10 weeks of gestation, the inferior and left part of Spiegel's lobe rode over the hepatoduodenal ligament and protruded medially into the lesser sac (bursa omentalis) behind the stomach. Thus, the fetal Winslow's foramen was located at the "superior" side of the ligament. However, as seen in adults, the protruding Spiegel's lobe was located at the posterior side of the lesser omentum. Therefore, a hypothetical rotation along the transverse axis in the later stages of development seems necessary to explain this repositioning. Considering that Spiegel's lobe develops faster than surrounding structures, it is likely that the lesser sac resulting from the rotation of the gastrointestinal tract, which actively contributes to facilitate the growth of the Spiegel lobe.

Totally laparoscopic left hemihepatectomy using ventral hilum exposure (VHE) for intrahepatic bile duct stone

The unique technique of ventral hilum exposure (VHE) was reported that it had excellent surgical outcomes in patients with intrahepatic bile duct stone. The basis of this surgical technique is that all the openings of the 2nd-order bile duct branches are exposed fully. In this article, we describe laparoscopic hemihepatectomy from using the VHE method in a patient with intrahepatic bile duct stone. Our patient was a 70-year-old female who had been diagnosed with an intrahepatic duct stone 30 years prior. Multiple intrahepatic bile duct stones in the left lateral section of the liver were revealed by abdominal computed tomography and magnetic resonance cholangiopancreatography. The patient resumed her oral intake on postoperative day 6. The patient had hyperbilirubinemia (10.3 mg/100 mL) on postoperative day 10. However, her serum bilirubin level decreased to 2.7 mg/100 mL on postoperative day 28. She was discharged without any serious complications on postoperative day 31. Totally laparoscopic left hemihepatectomy, using the VHE method, can be one option of surgical procedure in the near future, although a larger series of cases should be necessary to prove the feasibility of laparoscopic VHE.

Close relation between the inferior vena cava ligament and the caudate lobe in the human liver

BACKGROUND/PURPOSE

This study was conducted to clarify the real relation between the inferior vena cava (IVC) ligament and the caudate lobe in the human liver and also to elucidate their surgical importance in liver surgery.

METHODS

Specimens obtained from 20 adult cadaveric livers were submitted for the study. Histological structures of the IVC ligament and its relationship to the caudate lobe and the IVC were microscopically investigated.

RESULTS

The IVC ligament was a broad membranous connective tissue bridging the left and right side edges of the caval groove in which the IVC was embedded. At both edges of the caval groove, the IVC ligament was continuously transformed from the Glisson's capsules of the caudate and right lobes. The component of the portal triad, which originated from that of caudate lobe, and lymphatics were distributed in the IVC ligament without exception and ectopic hepatocytes existed in it in 4 of the 20 cases.

CONCLUSIONS

A close relation between the IVC ligament and the caudate lobe was confirmed. The findings suggested that the IVC ligament is a kind of degenerated hepatic tissue. When dissecting it, surgeons should manipulate it carefully to prevent unexpected bleeding and bile leakage.

Isolated laparoscopic resection of the hepatic caudate lobe: surgical technique and a report of 2 cases

The caudate lobe of the liver, segment 1 (S1), is located between the hepatic hilum and the inferior vena cava. Resection of S1 alone, without sacrificing other parts of the liver, is a surgical challenge. We present 2 cases of isolated laparoscopic resections of hepatic S1. We are the first to describe this laparoscopic technique. Two patients affected by colorectal liver metastases confined to S1 underwent laparoscopic isolated resections of S1 using a left approach. One of them also underwent left lateral segmentectomy. Both interventions were accomplished laparoscopically without conversion. Operative time for the first patient was 150 minutes and that for the second patient was 105 minutes. Blood loss was 200 and 100 mL for the first and second patients, respectively. There were no major intraoperative complications except for a tear in the inferior vena cava in the first patient that was repaired without the need for conversion. The postoperative course was uneventful for both patients. The duration of hospital stay was 10 and 8 days, respectively. The resected margins of the specimens were tumor-free (R0 resections). The 2 patients are alive and disease-free 7 and 5 months after the procedure. Isolated laparoscopic resection of the hepatic caudate lobe can be performed by a highly skilled surgeon, but should be performed only in selected cases.

Favorable outcomes of hilar duct oriented hepatic resection for high grade Tsunoda type hepatolithiasis

AIM: To evaluate the efficacy of hilar duct oriented hepatectomy for intractable hepatolithiasis, the ventral hilum exposure (VHE) method that has been applied by the authors.

METHODS: From June 1994 to June 2004 for a period of 10 years, 153 patients who had Tsunoda type III or IV hepatolithiasis, received hepatectomy at our institution. Among these patients, 128 who underwent hepatectomy by the VHE method were the subjects for the study. We analyzed the risk of this procedure, residual rate of intra-hepatic stones, and stone recurrent rates.

RESULTS: The average age was 54.2 years, and the male to female ratio was 1:1.7. The average follow-up period was 25.6 mo (6-114 mo). There was no post-operative severe complication or mortality after the operation. The rate of residual stones was 5.4% and the rate of recurrent stones was 4.2%.

CONCLUSION: VHE is a safe surgical procedure and provides favorable treatment results of intractable hepatolithiasis. Especially, this procedure has advantage in that intra-hepatic bile duct stricture may be confirmed and corrected directly during surgery.

Spiegel?s Lobe Bile Ducts Often Drain into the Right Hepatic Duct or Its Branches: Study Using Drip-Infusion Cholangiography-Computed Tomography in 179 Consecutive Patients

Using drip-infusion cholangiography-computed tomography (DIC-CT), we successfully identified the bile ducts draining the caudate lobe in 138 of 179 consecutive patients with extrahepatic cholelithiasis (179 ducts from Spiegel's lobe and 154 from the paracaval portion; 1-5 ducts per patient). The dorsal subsegmental duct of S8 (B8c) was often identified and could be discriminated from the paracaval caudate ducts, thus acting as a landmark for the right margin of the caudate lobe. Notably, in more than one-third of the 138 patients, at least one of the Spiegel's lobe ducts drained into the right hepatic duct or its branches (30.2% of the 179 ducts overall; all ducts joined branches of the right lobe in 25 patients). Similarly, 34.4% of the 154 paracaval caudate lobe ducts drained into the left hepatic duct or its branches. These "anatomical left/right dissociations" between the drainage territory and route were much more frequent than previously reported. Our results confirm the effectiveness of DIC-CT as a classical, noninvasive method for presurgical evaluation of the biliary system, but they also suggest that anatomical partial resection of the dorsal liver in patients with hilar cholangioma is often impossible because of contralateral biliary drainage.

Remaining caudate lobe in the right lobe graft in living donor liver transplantation: a blind spot?

The right margin of the caudate lobe is obscure. Therefore, a part of the caudate lobe (a part of the right side of the paracaval portion) seems almost always to remain with the right lobe graft during the standard harvesting procedure. We reviewed the intraoperative findings and the postoperative courses of donors and recipients of 11 consecutive living donor liver transplantations using right lobe grafts. Further, we used computed tomography during the postoperative course to investigate whether the remaining caudate lobe was present in the right lobe graft and whether it produced serious complications. Four recipients displayed an intraoperative bile leak from a remaining part of the caudate lobe after the completion of biliary reconstruction. With the exception of one case who developed repeated bile leakage from the same origin which eventually healed during a long-term postoperative course, Most recipients showed no postoperative biliary complications. Although a remaining caudate lobe was detected on postoperative computed tomography in all recipients, it produced no serious complications. In conclusion, a part of the right side of the paracaval portion of the caudate lobe almost always remains with a right lobe graft during the standard harvesting procedure. However, the implications of this phenomenon seem to be benign.

Human liver caudate lobe and liver segment

Recently, the caudate lobe has seemed to be the final target for aggressive cancer surgery of the liver. This lobe has five surfaces: the dorsal, left and hilar-free surfaces and the right and ventral-border planes. Surgeons have divided the caudate lobe into three parts: Spiegel's lobe, which is called the 'caudate lobe and papillary process' by anatomists, the caudate process, viewed as almost the same entity by anatomists, and the paracaval portion corresponding to the dorsally located parenchyma in front of the inferior vena cava. All three parts are supplied by primary branches originating from the left and right portal veins, including the hilar bifurcation area. The hilar bifurcation branch often (50%) supplies the paracaval portion and it sometimes (29%) extends its territory to Spiegel's lobe. It was postulated by Couinaud that the paracaval portion or the S9 is not defined by its supplying portal vein branch but by its 'dorsal location' in the liver. Couinaud's caudate lobe or dorsal-liver concept cause, and still now causes, great logical confusion for surgeons. We attempt here to describe the margins of the lobe, border branches of the portal vein, the left/right territorial border of the portal vein or Cantile's line and other topics closely relating to the surgery within these contexts. Finally, the caudate lobe as a liver segment will be discussed.

Location of the ventral margin of the paracaval portion of the caudate lobe of the human liver with special reference to the configuration of hepatic portal vein branches

The topographic anatomy of the ventral margin of the paracaval portion of the caudate lobe of the human liver has not been clearly described to date. To this end we hypothesize the existence of a precaudate plane, a flat or slightly curved plane defined by the ventral margins of the ligamentum venosum and the hilar plate. Using 76 cadaveric livers, we investigated whether the paracaval portion of the caudate lobe extended ventral to this plane and whether the paracaval caudate branch of the portal vein (PC) ran through this plane to its ventral side. In 28 of the specimens (36.8%), the PC extended over the plane to a variable depth: less than 10 mm in 10 specimens, 10-20 mm in 10, and more than 20 mm in eight specimens. This ventral extension of the PC consistently included its penetration into the dome-like area under the terminals of the three major hepatic veins; therefore, the ventrally extended PC often interdigitated with these veins and their tributaries (in practice, the ventral margin of the paracaval portion of the caudate lobe could generally be considered to run alongside the middle hepatic vein). Moreover, the ventral extension of the PC often reached the upper, diaphragmatic surface or the dorsal surface of the liver immediately to the right of the inferior vena cava. Several branches (termed border branches) in the ventral extension were difficult to identify as belonging to the PC. We discuss both the marginal configuration of the paracaval portion of the caudate lobe and how to identify and operate on the ventrally extended PC and related border branches during liver surgery.

The caudate lobe of the liver: implications of embryology and anatomy for surgery

The anatomy of the caudate lobe has technical and possibly oncologic implications for surgeons. The complex anatomy of the lobe is clarified by embryologic and anatomic analysis. This posterior sector is embryonically and anatomically independent of the right and left liver and the main portal fissure. The caudate lobe represents the only part of the liver that is in contact with the vena cava, except at the entrance of the main hepatic veins into the vena cava, and provides an anastomosis between the hepatic veins and vena cava. The entire caudate lobe is a single anatomic segment that is defined by the presence of portal venous and hepatic arterial branches, which supply the lobe, draining biliary ducts, and hepatic veins. Because no separate veins, arteries, or ducts can be defined for the right paracaval portion of the posterior liver and because pedicles cross the proposed division between the right and left caudate, the concept of segment IX is abandoned. The significance of caudate anatomy is reflected in the increase in the frequency and safety of major hepatic resection for primary and metastatic tumors in the liver. Right hepatic lobectomy routinely involves resection of the right portion of the caudate lobe (C. Couinaud, unpublished data, 1999). In the case of hilar bile duct cancer, which may extend into the dorsal ducts (especially the right lateral duct), partial or total caudate lobectomy is often necessary for complete extirpation of the tumor. Isolated caudate lobectomy can be performed for hepatocellular carcinoma that arises in the caudate lobe or for other tumors that arise in the lobe. The caudate lobe can be resected as part of the donor liver in preparation for a living related donor transplantation. Knowledge of the surgical anatomy of the caudate lobe is an essential part of the repertoire for surgeons who perform liver transplants or treat hepatobiliary cancer.