Impact of Tumor Size on the Difficulty of Laparoscopic Major Hepatectomies: An International Multicenter Study.

INTRODUCTION: Although tumor size (TS) is known to affect surgical outcomes in laparoscopic liver resection (LLR), its impact on laparoscopic major hepatectomy (L-MH) is not well studied. The objectives of this study were to investigate the impact of TS on the perioperative outcomes of L-MH and to elucidate the optimal TS cutoff for stratifying the difficulty of L-MH. METHODS: This was a post-hoc analysis of 3008 patients who underwent L-MH at 48 international centers. A total 1396 patients met study criteria and were included. The impact of TS cutoffs was investigated by stratifying TS at each 10-mm interval. The optimal cutoffs were determined taking into consideration the number of endpoints which showed a statistically significant split around the cut-points of interest and the magnitude of relative risk after correction for multiple risk factors. RESULTS: We identified 2 optimal TS cutoffs, 50 mm and 100 mm, which segregated L-MH into 3 groups. An increasing TS across these 3 groups (≤ 50 mm, 51-100 mm, > 100 mm), was significantly associated with a higher open conversion rate (11.2%, 14.7%, 23.0%, P < 0.001), longer operating time (median, 340 min, 346 min, 365 min, P = 0.025), increased blood loss (median, 300 ml,  ml, 400 ml, P = 0.002) and higher rate of intraoperative blood transfusion (13.1%, 15.9%, 27.6%, P < 0.001). Postoperative outcomes such as overall morbidity, major morbidity, and length of stay were comparable across the three groups. CONCLUSION: Increasing TS was associated with poorer intraoperative but not postoperative outcomes after L-MH. We determined 2 TS cutoffs (50 mm and 10 mm) which could optimally stratify the surgical difficulty of L-MH.

Robotic versus laparoscopic liver resections for hepatolithiasis: an international multicenter propensity score matched analysis.

INTRODUCTION: Minimally invasive liver resection (MILR) is widely recognized as a safe and beneficial procedure in the treatment of both malignant and benign liver diseases. Hepatolithiasis has traditionally been reported to be endemic only in East Asia, but has seen a worldwide uptrend in recent decades with increasingly frequent and invasive endoscopic instrumentation of the biliary tract for a myriad of conditions. To date, there has been a woeful lack of high-quality evidence comparing the laparoscopic (LLR) and robotic (RLR) approaches to treatment hepatolithiasis. METHODS: This is an international multicenter retrospective analysis of 273 patients who underwent RLR or LRR for hepatolithiasis at 33 centers in 2003-2020. The baseline clinicopathological characteristics and perioperative outcomes of these patients were assessed. To minimize selection bias, 1:1 (48 and 48 cases of RLR and LLR, respectively) and 1:2 (37 and 74 cases of RLR and LLR, respectively) propensity score matching (PSM) was performed. RESULTS: In the unmatched cohort, 63 (23.1%) patients underwent RLR, and 210 (76.9%) patients underwent LLR. Patient clinicopathological characteristics were comparable between the groups after PSM. After 1:1 and 1:2 PSM, RLR was associated with less blood loss (p = 0.003 in 1:2 PSM; p = 0.005 in 1:1 PSM), less patients with blood loss greater than 300 ml (p = 0.024 in 1:2 PSM; p = 0.027 in 1:1 PSM), and lower conversion rate to open surgery (p = 0.003 in 1:2 PSM; p < 0.001 in 1:1 PSM). There was no significant difference between RLR and LLR in use of the Pringle maneuver, median Pringle maneuver duration, 30-day readmission rate, postoperative morbidity, major morbidity, reoperation, and mortality. CONCLUSION: Both RLR and LLR were safe and feasible for hepatolithiasis. RLR was associated with significantly less blood loss and lower open conversion rate.

[Robotic Liver Resection for Liver Malignancy].

Robotic liver resection is a new platform for minimally invasive liver resection, and its functional advantages are expected to reduce or overcome the difficulties or limitations of laparoscopic liver resection, such as restricted instrument movement and unstable surgical visual field. Minimally invasive liver resection for malignancy, anatomic liver resection in particular, is technically demanding. In such type of difficult hepatectomy, robotic functions are suggested to confer benefits in vascular or biliary dissection, isolation and division during hilar dissection, as well as benefits in keeping stable visual field, vascular isolation, tying or clipping, and suture hemostasis during liver parenchymal dissection. Previous studies on minimally invasive anatomic liver resection has suggested that robotic liver resection is superior to laparoscopic liver resection in terms of perioperative outcomes including blood loss, postoperative complications, rate of open conversion, and length of hospital stay. There are also studies indicating that the long-term oncologic outcomes of robotic hepatectomy are comparable to those of open or laparoscopic hepatectomies. Furthermore, the usefulness of robot functions has increasingly been reported on cases of liver resection with biliary and vascular reconstruction. Robotic liver resection for malignancy is considered to be sufficiently effective and practical, with acceptable technical accuracy, safety, and cancer curability, particularly in highly difficult anatomic liver resection. Under these backgrounds, robotic liver resection has a potential to become the mainstay of minimally invasive liver resection for malignancy.

Early Changes in Alpha-Fetoprotein Are a Useful Predictor of Efficacy of Atezolizumab plus Bevacizumab Treatment in Patients with Advanced Hepatocellular Carcinoma.

INTRODUCTION: The aim of this study was to investigate the early changes in alpha-fetoprotein (AFP) and des-γ-carboxy prothrombin (DCP) levels in patients with advanced hepatocellular carcinoma (HCC) treated with atezolizumab plus bevacizumab and to evaluate the relationship between changes in these tumor markers and treatment efficacy. METHODS: Of 58 consecutive patients who started atezolizumab plus bevacizumab at our institution, 50 patients with information on antitumor response obtained at 6 weeks after therapy were enrolled in this study and their treatment outcomes were retrospectively evaluated. RESULTS: According to the Response Evaluation Criteria in Solid Tumors at 6 weeks, the objective response (OR) rate was 22.0% and the disease control (DC) rate was 78.0%. In patients who achieved OR at 6 weeks, median AFP and DCP ratios at weeks 1, 2, 3, and 6 were significantly lower than those in patients who did not achieve OR. AFP ratios in patients who did not achieve DC at 6 weeks (Non-6W-DC group) were significantly higher than in those who achieved DC at week 6 (6W-DC group). Median overall survival in the Non-6W-DC group was significantly shorter than in the 6W-DC group (156 days vs. not reached, p = 0.0008). An AFP ratio of 1.4 or higher at 3 weeks had a specificity of 88.0% and a sensitivity of 88.9% for predicting Non-6W-DC. Median progression-free survival was significantly shorter in patients with an AFP ratio of 1.4 or higher at 3 weeks than in those with an AFP ratio of <1.4 (42 days vs. 210 days, p = 0.0003). CONCLUSION: Early changes in AFP might be useful for predicting the antitumor efficacy of atezolizumab plus bevacizumab in patients with advanced HCC. An AFP ratio of 1.4 or higher at 3 weeks might be an early predictor of refractoriness to atezolizumab plus bevacizumab therapy.

Utility of the Iwate difficulty scoring system for laparoscopic right posterior sectionectomy: do surgical outcomes differ for tumors in segments VI and VII?

INTRODUCTION: The Iwate Score (IS) have not been well-validated for specific procedures, especially for right posterior sectionectomy (RPS). In this study, the utility of the IS was determined for laparoscopic (L)RPS and the effect of tumor location on surgical outcomes was investigated. METHODS: Post-hoc analysis of 647 L-RPS performed in 40 international centers of which 596L-RPS cases met the inclusion criteria. Baseline characteristics and perioperative outcomes of patients stratified based on the Iwate score were compared to determine whether a correlation with surgical difficulty existed. A 1:1 Mahalanobis distance matching was utilized to investigate the effect of tumor location on L-RPS outcomes. RESULTS: The patients were stratified into 3 levels of difficulty (31 intermediate, 143 advanced, and 422 expert) based on the IS. When using a stepwise increase of the IS excluding the tumor location score, only Pringle's maneuver was more frequently used in the higher surgical difficulty level (35.5%, 54.6%, and 65.2%, intermediate, advanced, and expert levels, respectively, Z = 3.34, p = 0.001). Other perioperative results were not associated with a statistical gradation toward higher difficulty level. 80 of 85 patients with a segment VI lesion and 511 patients with a segment VII lesion were matched 1:1. There were no significant differences in the perioperative outcomes of the two groups including open conversion, operating time, blood loss, intraoperative blood transfusion, postoperative stay, major morbidity, and mortality. CONCLUSION: Among patients undergoing L-RPS, the IS did not significantly correlate with most outcome measures associated with intraoperative difficulty and postoperative outcomes. Similarly, tumor location had no effect on L-RPS outcomes.

Laparoscopic isolated liver segmentectomy 8 for malignant tumors: techniques and comparison of surgical results with the open approach using a propensity score-matched study.

PURPOSE: Anatomic isolated liver segmentectomy 8 (ILSeg8) for malignancies remains technically challenging. The feasibility, safety, and oncologic validity of laparoscopic ILSeg8 are undefined, and thus were evaluated in comparison with the open approach. METHODS: This study enrolled 35 open and 29 laparoscopic ILSeg8 cases of hepatocellular carcinoma (n = 47), metastatic liver tumors (n = 16), and intrahepatic cholangiocarcinoma (n = 1) at our institution. The surgical techniques were based on the pre-hepatectomy extrahepatic Glissonian pedicle control, followed by cranial-to-caudal parenchymal dissection from the hepatic vein root side. The short- and long-term outcomes after ILSeg8 were retrospectively evaluated and compared between the open and laparoscopic approaches using 1:1 propensity score matching (PSM). RESULTS: Both before and after PSM, the laparoscopic ILSeg8 group had significantly less blood loss, lower postoperative serum bilirubin level, and a shorter postoperative hospital stay than the open group. The overall survival rates were comparable between the laparoscopic and open groups before (P = 0.017) and after (P = 0.043) PSM, with the similar recurrence-free survival rates between the groups. In a multivariable analysis of the cohort before PSM (n = 64), the laparoscopic approach was identified to be an independent factor for favorable overall survival (hazard ratio = 0.20, P = 0.039). CONCLUSION: Laparoscopic ILSeg8 using the extrahepatic Glissonian approach and hepatic vein root at first parenchymal dissection was feasible, safe, and oncologically acceptable. In ILSeg8 for malignancy, the laparoscopic approach potentially confers short-term advantages over the open approach with comparable long-term outcomes in select patients.

Eradication of Helicobacter pylori Induces Immediate Regressive Changes in Early Gastric Adenocarcinomas.

OBJECTIVE: Helicobacter pylori eradication is expected to prevent gastric cancer. However, morphological alterations after eradication often hinder accurate diagnosis. Therefore, we evaluated endoscopic and histological changes in gastric tumors after eradication of H. pylori in a time-dependent manner. METHODS: We classified 144 cases of endoscopic submucosal dissection (ESD) of early gastric cancer into the following categories: (i) patients positive for H. pylori with no eradication history, (ii) patients positive for H. pylori who underwent ESD 2 months after eradication, (iii) patients negative for H. pylori with an eradication history of at least 6 months before ESD, and (iv) patients negative for H. pylori with an unknown history. We compared endoscopic and histological factors between the groups. RESULTS: The characteristics of cancers positive for H. pylori were exploding shape, superficial high-grade atypical epithelium, and a surface proliferating zone. H. pylori eradication induced a series of endoscopic and histological changes, including shape -depression, appearance of surface regenerative and lower-grade atypical epithelium, and a downward shift of the proliferative zone within a period as short as 2 months. CONCLUSION: H. pylori eradication rapidly causes cancer regression and leads to tumor shrinkage, diminished atypism, and shortened proliferative zone, resulting in drastic morphological changes.

Repeat hepatectomy with systemic chemotherapy might improve survival of recurrent liver metastasis from colorectal cancer-a retrospective observational study.

BACKGROUND: Although hepatectomy for metastatic colorectal cancer (mCRC) prolongs survival in up to 40% of people, recurrence rates approach 70%. We used a multidisciplinary approach to treat recurrent liver metastases, including chemotherapy, surgery, and palliative care. On the other hand, development of chemotherapeutic agents is remarkable and improves long-term survival. However, whether chemotherapy and repeat hepatectomy combination therapy improve survival or not is still unclear. The aim of this study was to analyze the outcomes of repeat hepatectomy with systemic chemotherapy for mCRC. METHODS: Following Institutional Review Board approval, we reviewed the records of all patients who underwent hepatectomy for mCRC between 1974 and 2015 at Fujita Health University Hospital. We used the Kaplan-Meier method to estimate overall survival from the first and last hepatectomy in multi hepatectomy cases after 2005 and compared outcomes between groups using the log-rank test. RESULTS: A total of 426 liver resections were performed for mCRC; of these, 236 cases were performed after 2005 (late group). In 118 (50%) cases, the site of recurrence was the liver, 59 (50%) underwent repeat hepatectomy, and 14 cases had ≥ 2 repeat hepatectomies. Overall survival (OS) before and after 2005 was 42.2 and 64.1 months, respectively, with the late group having better OS compared to the early (1974-2004) group. OS for single hepatectomy cases was 83.2 months, for two hepatectomies was 42.9 months, and for three hepatectomies was 35.3 months. In total, 59 patients did not undergo surgery after recurrence with an OS of 28.7 months. Mortality of the second and third repeat hepatectomy was 1.7% and 15.3%, respectively. CONCLUSION: Repeat hepatectomy with systemic chemotherapy for mCRC is feasible and might achieve improved survival in carefully selected patients.

Short-term detection of gastric genotoxicity using the DNA double-strand break marker γ-H2AX.

DNA damage caused by Helicobacter pylori infection and chronic inflammation or exposure to genotoxic agents is considered an important risk factor of gastric carcinogenesis. In this study, we have evaluated a short-term technique to detect DNA damage response to various chemical carcinogens; it involves visualization of Ser 139-phosphorylated histone H2AX (γ-H2AX) foci by immunohistochemistry and expression analysis of other genes by quantitative RT-PCR. Six-week-old male rats were intragastrically administered N-methyl-N-nitrosourea (MNU), 3,2'-dimethyl-4-aminobiphenyl (DMAB), dimethylnitrosamine (DMN), and 1,2- dimethylhydrazine (DMH) for 5 days/week for 4 weeks, using corn oil as a vehicle. Animals were sacrificed at day 28, and their stomachs were excised. γ-H2AX foci formation, indicating DNA double-strand breaks, was observed in the proliferative zone of both fundic and pyloric glands. The number of positive cells per gland was significantly high in pyloric glands in the MNU group and in fundic glands in the MNU and DMAB groups. A significant increase in p21waf1 mRNA level was observed in the DMN group compared with the control, which was in contrast to the decreasing tendency of the h2afx mRNA level in the MNU and DMN groups. Apoptotic cells positive for γ-H2AX pan or peripheral nuclear staining were observed on the surface layer of the fundic mucosa in the MNU group. The fundic pepsinogen a5 (pga5) mRNA level showed a significant decrease, indicating gland damage. The pyloric pepsinogen c mRNA level showed no change. In conclusion, γ-H2AX in combination with other gene expression analyses could be a useful biomarker in a short-term experiment on gastric chemical genotoxicity.

[Successful Conversion Therapy for Gastric Cancer with Paraaortic Lymph Node Metastasis after SP Therapy-A Case Report].

A 69-year-old woman, who complained of loss of appetite, was admitted to our hospital and diagnosed with clinical Stage Ⅳgastric cancer and paraaortic lymph node metastases(cT4aN3M1[#16b1LYM], cStage Ⅳ). She underwent 2 cycles of SP therapy(combination of S-1 and CDDP). A partial response of the primary tumor was noted, with no distant metastases, except for the paraaortic lymph nodes. She underwent robotic total gastrectomy with D2 plus paraaortic lymph node dissection. Histopathology showed no residual tumor cells in the stomach or lymph nodes. Postoperatively, the patient underwent 3 cycles of SOX therapy(combination of S-1 and oxaliplatin)and survived for over 6 postoperative months, with no recurrences. For advanced gastric cancers with paraaortic lymph node dissection with no evidences of other distant metastases, gastrectomy with paraaortic lymph node dissection combined with chemotherapy could be a therapeutic option to achieve R0 resection.

[A Case of Robot-Assisted Conversion Surgery for Gastric Cancer with Peritoneal Dissemination That Responded to Intravenous and Intraperitoneal Paclitaxel Combined with S-1 Chemotherapy].

This case involved a 69-year-old female patient with peritoneal dissemination of an advanced gastric cancer. She underwent chemotherapy comprisingintravenous and intraperitoneal paclitaxel combined with S-1. After 20 courses, a staging laparoscopy was performed, and pathological analysis of the peritoneal dissemination and cytologic analysis of ascites fluid yielded negative results. A radical robot-assisted total gastrectomy was successfully performed. The pathological stage was determined to be ypT4aN2M0, ypStage ⅢB. We continued to administer the same chemotherapy regimen for 15 courses (total: 35 courses)after surgery. No recurrence has been detected during the 1-year period after surgery.

[A Case of Duodenal Gastrointestinal Stromal Tumor Resection with Preservation of the Pancreatic Head Following Chemotherapy with Imatinib].

A 60-year-old male was admitted to our hospital on account of a duodenal submucosal tumor on the opposite side of Vater's papilla identified on a screening gastroduodenoscopy. The tumor was diagnosed as a duodenal gastrointestinal stromal tumor(GIST)due to positive c-kit and DOG1tests. Gastroduodenography and enhanced computed tomography showed a 50mm tumor widely invadingthe descendingportion of the duodenum close to the papilla of Vater and indicated the need for extended resection includingpancreaticoduodenectomy to achieve curation. Preoperative chemotherapy was initiated with imatinib mesylate(imatinib)to preserve the pancreas. A 16 month course of imatinib shrunk the tumor up to 21mm and laparoscopic partial duodenectomy was performed as a curative resection. So far, no local tumor recurrence has been seen for 26 months after the surgery. Herein, we report this case with a review of the literature.

Successful living donor liver transplantation for classical maple syrup urine disease.

MSUD is an autosomal recessive condition characterized by a deficiency in the enzyme, BCKDH, which catalyzes the breakdown of BCAAs. If left untreated, MSUD can result in mental retardation, central nervous system disorders, and even death. Most patients with MSUD are treated with a restricted protein diet and milk from which BCAAs have been removed. LT has been shown effective in patients with MSUD. This report describes the case of a 15-month-old boy who received a liver graft from his mother. Transplantation was successful, and the patient was then able to ingest a normal diet. Despite episodes of acute rejection, chylous ascites, and high fever (40 °C), he has shown no evidence of MSUD recurrence. These findings indicate that patients with MSUD can be successfully treated by LDLT, even when the donor is a heterozygous carrier of a mutated BCKDH gene.

Recommendations for laparoscopic liver resection: a report from the second international consensus conference held in Morioka.

The use of laparoscopy for liver surgery is increasing rapidly. The Second International Consensus Conference on Laparoscopic Liver Resections (LLR) was held in Morioka, Japan, from October 4 to 6, 2014 to evaluate the current status of laparoscopic liver surgery and to provide recommendations to aid its future development. Seventeen questions were addressed. The first 7 questions focused on outcomes that reflect the benefits and risks of LLR. These questions were addressed using the Zurich-Danish consensus conference model in which the literature and expert opinion were weighed by a 9-member jury, who evaluated LLR outcomes using GRADE and a list of comparators. The jury also graded LLRs by the Balliol Classification of IDEAL. The jury concluded that MINOR LLRs had become standard practice (IDEAL 3) and that MAJOR liver resections were still innovative procedures in the exploration phase (IDEAL 2b). Continued cautious introduction of MAJOR LLRs was recommended. All of the evidence available for scrutiny was of LOW quality by GRADE, which prompted the recommendation for higher quality evaluative studies. The last 10 questions focused on technical questions and the recommendations were based on literature review and expert panel opinion. Recommendations were made regarding preoperative evaluation, bleeding controls, transection methods, anatomic approaches, and equipment. Both experts and jury recognized the need for a formal structure of education for those interested in performing major laparoscopic LLR because of the steep learning curve.

The First Prospective Study Investigating the Safety and Feasibility of a Spray-Type Adhesion Barrier (AdSpray™) in Minimally Invasive Hepatectomy: An Analysis of 124 Cases at Our Institution.

(1) Background: With the increasing demand for repeat hepatectomy, preventing perihepatic adhesion formation following initial hepatectomy is crucial. Adhesion-preventative barriers, like the new spray-type AdSprayTM (Terumo Corporation, Tokyo, Japan), have been proposed to reduce adhesion risk. However, data on their safety in minimally invasive hepatectomy (MIH) remain scarce. This is the first prospective study to evaluate the safety and feasibility of AdSprayTM in MIH. (2) Methods: A total of 124 patients who underwent MIH with AdSprayTM and 20 controls were analyzed. Subgroup analysis according to the AdSpray™ application area was conducted. Major complications were assessed using the Clavien-Dindo classification. Moreover, intraperitoneal pressure during AdSpray™ application was monitored in 20 cases. (3) Results: Major complications occurred in 6.4% of the patients, which was comparable to that in open hepatectomy. Intraperitoneal pressure remained stable below 12 mmHg during AdSpray™ application without any complications. No significant difference in complication rates was observed among subgroups. However, a potential increase in intra-abdominal abscess formation was suspected with AdSpray™ application to the resected liver surfaces. (4) Conclusions: AdSpray™ can be safely used in MIH; however, further research is needed to confirm the appropriacy of using AdSpray™, particularly over resected liver surfaces. Overall, AdSpray™ is a promising tool for enhancing the safety of MIH.

Impact of Minimally Invasive Surgery on Anatomic Liver Segmentectomy Using the Extrahepatic Glissonean Approach.

Accurate minimally invasive anatomic liver (sub)segmentectomy (MIAS) is technically demanding and not yet standardized, and its surgical outcomes are undefined. To study the impact of the minimally invasive approach on perioperative outcomes of anatomic liver (sub)segmentectomy (AS), we retrospectively studied and compared perioperative outcomes of 99 open AS (OAS) and 112 MIAS (laparoscopic 77, robotic 35) cases using the extrahepatic Glissonean approach, based on the 1:1 propensity score matched analyses. After matching (71:71), MIAS was superior to OAS in terms of blood loss (p < 0.0001), maximum postoperative serum total bilirubin (p < 0.0001), C-reactive protein (p = 0.034) levels, R0 resection rate (p = 0.021), bile leak (p = 0.049), and length of hospital stay (p < 0.0001). The matched robotic and laparoscopic AS groups (30:30) had comparable outcomes in terms of operative time, blood loss, transfusion, open conversion, postoperative morbidity and mortality, R0 resection, and hospital stay, although the rate of Pringle maneuver application (p = 0.0002) and the postoperative aspartate aminotransferase level (p = 0.002) were higher in the robotic group. Comparing the matched posterosuperior (sub)segmentectomy cases or unmatched repeat hepatectomy cases between MIAS and OAS, we observed significantly less blood loss and shorter hospital stays in MIAS. Robotic AS yielded comparable outcomes with laparoscopic AS in the posterosuperior (sub)segmentectomy and repeat hepatectomy settings, despite the worse tumor and procedural backgrounds in robotic AS. In conclusion, various types of MIAS standardized by the extrahepatic Glissonean approach were feasible and safe with more favorable perioperative outcomes than those of OAS. Although robotic AS had almost comparable outcomes with laparoscopic AS, robotics may serve to decrease the surgical difficulty of MIAS in selected patients undergoing posterosuperior (sub)segmentectomy and repeat hepatectomy.

Hepatic vein anatomy related to Laennec's capsule for liver resection.

BACKGROUND: Laennec's capsule is the proper membrane covering the entire surface of the liver parenchyma, including around the Glissonean pedicles and hepatic veins. Laennec's capsule around the hepatic veins has been clinically reported to comprise two layers: the hepatic and cardiac Laennec's capsules. However, where the cardiac Laennec's capsule is derived from and the two capsules' separability are still unclear. This study aimed to investigate the anatomy of the two capsules using cadaveric specimens. METHODS: Histopathological examinations of autopsy specimens from four cadavers were conducted. Each specimen was sliced in the longitudinal section to include the pericardium, right hepatic vein (RHV), and inferior vena cava (IVC). Additionally, long-axis specimens of the RHV were obtained to determine the separability of the capsules and to examine the extent to which the capsules extended along the RHV. Laennec's capsule was estimated using elastic fiber staining. RESULTS: The cardiac Laennec's capsule is derived from the pericardium (parietal and visceral) and diaphragm and runs parallel with the IVC and hepatic veins associated with the hepatic Laennec's capsule. The two capsules were separable micro- and macroscopically. The hepatic Laennec's capsule was observed from the root to the peripheral side and the cardiac Laennec's capsule from the root to the middle side of the hepatic vein. CONCLUSIONS: The existence of the two layers of Laennec's capsule around the hepatic veins was confirmed histologically and they were separable. Identification and decollement of these layers would contribute to establishing safe and feasible anatomic liver resection techniques.