Identification of segments VI and VII of the liver based on the ramification patterns of the intrahepatic portal and hepatic veins

Prevalence and clinical significance of the Sg6/Sg7 intersegmental veins based on re-evaluation of the Couinaud classification for the right posterior portal vein

Although Segment 6(Sg6) and Segment 7(Sg7) are two independent units, there are currently no clear anatomical boundary markers between Sg6 and Sg7. This study aimed to identify intersegmental veins (ISV) in the intersegmental plane of Sg6 and Sg7, and evaluate the prevalence of ISV, and its clinical significance in anatomical hepatectomy. We analyzed data from 180 patients undergoing abdominal computed tomography (CT) examination, and simultaneously performed 3D reconstruction models of the liver for each patient. The right posterior portal vein was analyzed and re-typed. Furthermore, the existence of ISV was defined, and prevalence and confluence patterns of ISV were analyzed. The author attempted to apply ISV to laparoscopic S6/S7 segmentectomy. We sorted data from the right posterior portal vein and divided it into six types. The ISV could be identified in 82.2% (148/180) of the patients, which were derived from the right hepatic vein (RHV) (91.9%) and right posterior inferior vein (IRHV) (8.1%). Ten ISV-guided laparoscopic Sg6/Sg7 segmentectomy were successfully carried out, seven patients underwent Sg6 segmentectomy, and three patients underwent Sg7 segmentectomy. There was no perioperative mortality. The median operative time was 223 min (range 181-260 min). The median blood loss was 200 ml (range 150-310 ml). The R0 resection rate was 100%. The ISV may be a candidate vessel to distinguish the boundary of the right posterior sector; it is expected to be a landmark in the liver parenchyma of anatomical hepatectomy.

Double cone-unit laparoscopic hepatic resection for tumors adjacent to the hepatic vein

BACKGROUND

In tumor adjacent to the hepatic vein, it is important to treat two tertiary Glissonean pedicles that straddle to the hepatic vein in order to remove the tumor with a negative margin. The anatomical resection of the smallest unit may be considered to be the resection of the double cone-unit (DCU) in small tumor adjacent to the vein.

PATIENTS AND METHODS

127 patients who had undergone laparoscopic hepatectomy at the Jikei Medical University Hospital from 2020 through 2021. In 5 cases, Laparoscopic DCU resection was performed. If the CT image shows a hepatic vein near the tumor and the tumor is relatively small, less than 50 mm in size, DCU resection should be considered. After approaching the target Glissonean pedicles, the Bulldog Clamps were used to testing clamp it. After clamping it, the ICG was injected from peripheral veins. A few minutes later, the tumor-bearing portal territory could be identified as negative regions of fluorescence in the near infrared imaging system. The target hepatic vein, which runs between the two territories, was dissected where it transitions from the first to the second territory.

RESULTS

The median operative time in these 5 patients was 279 min, and the median volume of blood loss was 290 g. The average tumor size was 33 mm and the average surgical margin was 4.5 mm.

CONCLUSION

In small tumor adjacent to the hepatic vein, the anatomical hepatectomy of the smallest unit may be the Double Cone-Unit resection.

Long-Term Outcomes of Mesohepatectomy for Centrally Located Liver Tumors: Two-Decade Single-Center Experience

BACKGROUND

Mesohepatectomy is a viable treatment option for patients diagnosed with centrally located liver tumors (CLLTs). There are several reports from Eastern centers, but few data are available on this topic from Western centers.

STUDY DESIGN

Data of 128 consecutive patients who underwent mesohepatectomy between September 2000 and September 2020 in our center were analyzed from a prospectively collected database. Patient demographic data, liver tumor characteristics, and intraoperative data were collected. In addition, posthepatectomy bile leakage (PHBL), posthepatectomy hemorrhage (PHH), posthepatectomy liver failure (PHLF), and 90-day mortality after mesohepatectomy were assessed. Long-term outcomes were also reported, and factors that may influence disease-free survival were evaluated.

RESULTS

Of 128 patients, 113 patients (88.3%) had malignant hepatic tumors (primary and metastatic tumors in 41 [32%] and 72 [56.3%] patients, respectively), and 15 patients suffered from benign lesions (11.7%). Among the relevant surgical complications (grade B or C), PHBL was the most common complication after mesohepatectomy and occurred in 11.7% of patients, followed by PHLF in 3.1% of patients and PHH in 2.3% of patients. Only four patients (3.1%) died within 90 days after mesohepatectomy. The 5-year overall survival and overall recurrence (for malignant lesion) rates were 76.5% and 45.1%, respectively.

CONCLUSION

Mesohepatectomy is a safe and feasible surgical treatment with low morbidity and mortality for patients with CLLT. Long-term outcomes can be improved by increased surgical expertise.

Feasibility of Right Upper Transversal Hepatectomy in the Absence of an Inferior Right Hepatic Vein: New Insights regarding This Complex Procedure

Background

Right upper transversal hepatectomy (RUTH) is defined as the removal of liver segments 7, 8, and 4A with ligature of the right and middle hepatic veins and is considered one of the most complex techniques of parenchymal-sparing hepatectomies. This procedure can be performed, without venous reconstruction, if collateral veins are present communicating within remnant liver segments to a large inferior right hepatic vein and/or to the left hepatic vein. This venous network could maintain outflow from the inferior right segments (S5, S6) to the left liver when a RUTH is performed, even in the absence of an inferior right hepatic vein. The aim of this study is to present our experience with RUTH without venous reconstruction in patients with and without the presence of an inferior right hepatic vein (IRHV).

Methods

Patients submitted to RUTH for treatment of liver metastases were selected from our database. The presence of an IRHV, clinical and surgical characteristics of the patients, immediate outcomes, viability of liver segments 5 and 6, and long-term survival were analyzed.

Results

RUTH was successfully performed in four patients. In two patients, IRHV was not present, but intrahepatic communicating veins between proximal right and middle hepatic veins and left hepatic vein were present. No venous reconstructions were performed. Mild congestion of the inferior right segments occurred in the patients where there was no IRHV but no immediate, early, or late complications were observed.

Conclusions

RUTH is feasible and can be performed even in the absence of an IRHV, without venous reconstruction. Some degree of congestion of the right inferior liver segments might occur when an IRHV is absent, yet this is not clinically significant when communicating veins are present. Maximum parenchyma preservation might prevent postoperative liver failure and allow repeated resections in case of hepatic recurrence.

Landmarks to identify segmental borders of the liver: A review prepared for PAM-HBP expert consensus meeting 2021

BACKGROUND

In preparation for the upcoming consensus meeting in Tokyo in 2021, this systematic review aimed to analyze the current available evidence regarding surgical anatomy of the liver, focusing on useful landmarks, strategies and technical tools to perform precise anatomic liver resection (ALR).

METHODS

A systematic review was conducted on MEDLINE/PubMed for English articles and on Ichushi database for Japanese articles until September 2020. The quality assessment of the articles was performed in accordance with the Scottish Intercollegiate Guidelines Network (SIGN).

RESULTS

A total of 3169 manuscripts were obtained, 1993 in English and 1176 in Japanese literature. Subsequently, 63 English and 20 Japanese articles were selected and reviewed. The quality assessment of comparative series and case series was revealed to be usually low; only six articles were qualified as high quality. Forty-two articles focused on analyzing intersegmental/sectional planes and their relationship with specific hepatic landmark veins. In 12 articles, the authors aimed to investigate liver surface anatomic structures, while 36 articles aimed to study technological tools and contrast agents for surgical segmentation during ALR. Although Couinaud's classification has remained the cornerstone in daily diagnostic/surgical practices, it does not always portray the realistic liver segmentation and there has been no standardization on which a single strategy should be followed to perform precise ALR.

CONCLUSIONS

A global consensus should be pursued in order to establish clear guidelines and proper recommendations to perform ALR in the era of minimally invasive surgery.

Re-evaluation of the Couinaud classification for segmental anatomy of the right liver, with particular attention to the relevance of cranio-caudal boundaries

BACKGROUND

Although the Couinaud classification of liver segments has been challenged by several studies, whether the cranio-caudal boundaries can be delineated in the right liver has not yet been assessed. This study scrutinized the third-order branching pattern of the portal vein in the right liver with attention to the validity of cranio-caudal segmentation.

METHODS

Three-dimensional reconstruction of the portal vein and hepatic vein, using non-contrast-enhanced magnetic resonance imaging was performed in 50 healthy participants.

RESULTS

In the right paramedian sector, the portal vein ramified into 2 thick P8s (P8vent and P8dor) in all the participants. Additional thick P8s that ran laterally and/or medially (P8lat and/or P8med) were observed in 18 (32%) participants. In contrast, multiple thin P5s, ranging in number from 2 to 6 (median, 4), branched from the right paramedian trunk, the right portal trunk, and/or even from P8s. In the right lateral sector, an arch-like type in which multiple P6s ramified from a single thick P7 was observed in 26 (52%) participants. A bifurcation type composed of a single P7 and a single P6 was observed in 23 (46%) participants, and a trifurcation type was observed in 1 participant.

CONCLUSION

No clear cranio-caudal intersegmental plane could be delineated in the right liver in most of the participants. The resection of a whole Couinaud segment in the right liver should not be regarded as a systematic, anatomic resection from an oncologic viewpoint. In contrast, detailed information on the third-order portal vein ramification pattern is likely to be helpful when performing smaller anatomic resections.

Three-dimensional analysis of the segmental arrangement of lower lung lobes in human fetuses: is this arrangement a miniature version of adult morphology?

Knowledge of the lung segment system is essential for understanding human anatomy and has great clinical relevance. The arrangement of 11 segments, including the S* or subsuperior segment, and its individual variations, are considered to be the same in fetal and adult lungs. The present study assessed the topographical anatomy of lower segmental and subsegmental bronchi by computer-assisted three-dimensional imaging of serial sagittal sections of both lungs of 22 embryos and fetuses of gestational age 6-7 weeks (crown-rump length 15.0-28.5 mm). Long inferior courses of B8b (basal) and B10c (medial) were observed in sagittal sections of both lungs. B8a (lateral) and B10b (lateral) in the right lungs were consistently underdeveloped, with S9 occupying most of the lateral half of the lower lobe. In some samples, B6b (lateral) did not reach the lateral surface. The lateral dominance of S9 was also seen in the left lungs. Some B* candidates were present, but B7 candidates were absent. Lateral and posterior expansions of S6b, S8a and S10b to cover S9 were observed in additional midterm and near-term lung sections, indicating that the original S9 dominance was 'corrected' by an increase in lung volume. Delayed growth of the lower lateral subsegments might induce mechanical stress, resulting in aberrant notches or fissures, such as those separating an independent posterior lobe. The segmental arrangement of fetal lungs was not stable, but was altered over a long fetal period after the complete subsegmental division of the bronchi, except for the minor bronchi B* and B7.

Right hepatic venous system variation in living donors: a three-dimensional CT analysis

BACKGROUND

The right hepatic venous system consists of the right hepatic vein (RHV) and inferior RHVs (IRHVs). When the right posterior section is used as a graft for liver transplantation, understanding variations and relationships between the RHV and IRHVs is critical for graft venous return and hepatic vein reconstruction. This study aimed to evaluate variations in the hepatic veins and the relationships between them.

METHODS

The medical records and CT images of patients who underwent hepatectomy as liver donors were assessed retrospectively. The relationship between the veins was evaluated by three-dimensional CT.

RESULTS

The configuration of the posterior section was classified into one of eight types based on the RHV and IRHVs in 307 patients. Type 1a (103 of 307), type 1b (139 of 307) and type 2a (40 of 307) accounted for 91·9 per cent of the total. The diameter of the RHV extending towards the inferior vena cava had a significant inverse correlation with that of the IRHV (r²  = -0·615, P < 0·001). Type 1a, which had no IRHVs, had the RHV with the largest diameter; conversely, type 2a, which had a large IRHV, had the RHV with the smallest diameter.

CONCLUSION

The hepatic venous system of the right posterior section was classified into eight types, with an inverse relationship between RHV and IRHV sizes. This information is useful for segment VII resection or when the right liver is used as a transplant graft.

Practical guidelines for the use of technetium-99m mebrofenin hepatobiliary scintigraphy in the quantitative assessment of liver function

Surgical resection remains the most important curative treatment for liver tumors; however, it harbors the risk of developing posthepatectomy liver failure. The principal risk is associated with the quality and quantity of the future remnant liver. Therefore, preoperative assessment of the future remnant liver is essential in patients scheduled for major liver resection. Technetium-99m mebrofenin hepatobiliary scintigraphy (HBS) in combination with single-photon emission computed tomography/computed tomography is increasingly applied for the quantitative assessment of liver function before major liver surgery. This dynamic quantitative liver function test allows assessment of both total and regional liver function, represented by the hepatic mebrofenin uptake rate, thereby assisting in adequate patient selection. Since routine implementation, it has shown to reduce the risk of posthepatectomy liver failure and has proven to be more valuable than volumetric assessment. To ensure optimal and reproducible results that can be compared across different centers, it is crucial to standardize the methodology and ensure practical applicability of this technique, thereby facilitating external validation and multicenter trials. This article provides an overview of the HBS methodology used at some of the largest HBS centers and covers practical details in the application of HBS for the quantitative scintigraphic assessment of liver function.

Oncologic superiority of anatomic resection of hepatocellular carcinoma by ultrasound-guided compression of the portal tributaries compared with nonanatomic resection: An analysis of patients matched for tumor characteristics and liver function

BACKGROUND

The superiority of anatomic resection compared with nonanatomic resection for hepatocellular carcinoma remains a matter of debate. Further, the technique for anatomic resection (dye injection) is difficult to reproduce. Anatomic resection using a compression technique is an easy and reversible procedure based on liver discoloration after ultrasound-guided compression of the tumor-feeding portal tributaries. We compared the oncologic efficacy of compression technique anatomic resection with that of nonanatomic resection.

METHODS

Among patients with resected hepatocellular carcinoma, patients who underwent compression technique anatomic resection were matched 1-to-2 with nonanatomic resection cases based on the Child-Pugh class, Model for End-Stage Liver Disease score, cirrhosis, hepatocellular carcinoma number (1/>1), and hepatocellular carcinoma size (>30, 30-50, and >50 mm). The exclusion criteria were nonanatomic resection because of severe cirrhosis, major hepatectomy, 90-day mortality (0 compression technique anatomic resection), non-cancer-related death, and follow-up <12 months. A total of 47 patients who underwent compression technique anatomic resection were matched with 94 nonanatomic resection cases.

RESULTS

All patients were Child-Pugh A, and 53% were cirrhotic. Liver function tests and signs of portal hypertension were similar between the groups. There was 1 hepatocellular carcinoma in 81% of the patients, and the hepatocellular carcinoma was ≥30 mm in 68%. Patients undergoing anatomic resection with compression had better 5-year survival (77% vs 60%; risk ratio = 0.423; P = .032; multivariable analysis), less local recurrences (4% vs 20%; P = .012), and better 2-year local recurrence-free survival (94% vs 78%; P = .012). Nonlocal recurrence-free survival was similar between the groups. The compression technique anatomic resection group more often had repeat radical treatment for recurrence (68% vs 28%; P = .0004) and had better 3-year survival after recurrence (65% vs 42%; P = .043).

CONCLUSION

Compression technique anatomic resection appears to provide a more complete removal of the hepatocellular carcinoma-bearing portal territory. Local disease control and survival are better with compression technique anatomic resection than with nonanatomic resection.

Open Liver Resection, Laparoscopic Liver Resection, and Percutaneous Thermal Ablation for Patients with Solitary Small Hepatocellular Carcinoma (≤30 mm): Review of the Literature and Proposal for a Therapeutic Strategy

BACKGROUND

Patients with a single hepatocellular carcinoma (HCC) ≤3 cm and preserved liver function have the highest likelihood to be cured if treated. The most adequate treatment methods are yet a matter that is debated.

METHODS

We reviewed the literature about open anatomic resection (AR), laparoscopic liver resection (LLR), and percutaneous thermal ablation (PTA).

RESULTS

PTA is effective as resection for HCC < 2 cm, when they are neither subcapsular nor perivascular. PTA in HCC of 2-3 cm is under evaluation. AR with the removal of the tumor-bearing portal territory is recommended for HCC > 2 cm, except for subcapsular ones. In comparison with open surgery, LRR has better short-term outcomes and non-inferior long-term outcomes. LLR is standardized for superficial limited resections and for left-sided AR.

CONCLUSIONS

According to the available evidences, the following therapeutic proposal can be advanced. Laparoscopic limited resection is the standard for any subcapsular HCC. PTA is the first-line treatment for deep-located HCC < 2 cm, except for those in contact with Glissonean pedicles. Laparoscopic AR is the standard for deep-located HCC of 2-3 cm of the left liver, while open AR is the standard for deep-located HCC of 2-3 cm in the right liver. HCC in contact with Glissonean pedicles should be scheduled for resection (open or laparoscopic) independent of their size. Liver transplantation is reserved to otherwise untreatable patients or as a salvage procedure at recurrence.

Risk score to predict biliary leakage after elective liver resection

Background

Biliary leakage remains a major cause of morbidity after liver resection. Previous prognostic studies of posthepatectomy biliary leakage (PHBL) lacked power, population homogeneity, and model validation. The present study aimed to develop a risk score for predicting severe PHBL.

Methods

In this multicentre observational study, patients who underwent liver resection without hepaticojejunostomy in one of nine tertiary centres between 2012 and 2015 were randomly assigned to a development or validation cohort in a 2 : 1 ratio. A model predicting severe PHBL (International Study Group of Liver Surgery grade B/C) was developed and further validated.

Results

A total of 2218 procedures were included. PHBL of any severity and severe PHBL occurred in 141 (6·4 per cent) and 92 (4·1 per cent) patients respectively. In the development cohort (1475 patients), multivariable analysis identified blood loss of at least 500 ml, liver remnant ischaemia time 45 min or more, anatomical resection including segment VIII, transection along the right aspect of the left intersectional plane, and associating liver partition and portal vein ligation for staged hepatectomy as predictors of severe PHBL. A risk score (ranging from 0 to 5) was built using the development cohort (area under the receiver operating characteristic curve (AUROC) 0·79, 95 per cent c.i. 0·74 to 0·85) and tested successfully in the validation cohort (AUROC 0·70, 0·60 to 0·80). A score of at least 3 predicted an increase in severe PHBL (19·4 versus 2·6 per cent in the development cohort, P &lt; 0·001; 15 versus 3·1 per cent in the validation cohort, P &lt; 0·001).

Conclusion

The present risk score reliably predicts severe PHBL. It represents a multi-institutionally validated prognostic tool that can be used to identify a subset of patients at high risk of severe PHBL after elective hepatectomy.

Portal Vein Embolization as an Oncosurgical Strategy Prior to Major Hepatic Resection: Anatomic, Surgical, and Technical Considerations

Preoperative portal vein embolization (PVE) is used to extend the indications for major hepatic resection, and it has become the standard of care for selected patients with hepatic malignancies treated at major hepatobiliary centers. To date, various techniques with different embolic materials have been used with similar results in the degree of liver hypertrophy. Regardless of the specific strategy used, both surgeons and interventional radiologists must be familiar with each other's techniques to be able to create the optimal plan for each individual patient. Knowledge of the segmental anatomy of the liver is paramount to fully understand the liver segments that need to be embolized and resected. Understanding the portal vein anatomy and the branching variations, along with the techniques used to transect the portal vein during hepatic resection, is important because these variables can affect the PVE procedure and the eventual surgical resection. Comprehension of the advantages and disadvantages of approaches to the portal venous system and the various embolic materials used for PVE is essential to best tailor the procedures for each patient and to avoid complications. Before PVE, meticulous assessment of the portal vein branching anatomy is performed with cross-sectional imaging, and embolization strategies are developed based on the patient's anatomy. The PVE procedure consists of several technical steps, and knowledge of these technical tips, potential complications, and how to avoid the complications in each step is of great importance for safe and successful PVE and ultimately successful hepatectomy. Because PVE is used as an adjunct to planned hepatic resection, priority must always be placed on safety, without compromising the integrity of the future liver remnant, and close collaboration between interventional radiologists and hepatobiliary surgeons is essential to achieve successful outcomes.

The student's dilemma, liver edition: incorporating the sonographer's language into clinical anatomy education

Anatomy students are often confused by multiple names ascribed to the same structure by different clinical disciplines. Increasingly, sonography is being incorporated into clinical anatomical education, but ultrasound textbooks often use names unfamiliar to the anatomist. Confusion is worsened when ultrasound names ascribed to the same structure actually refer to different structures. Consider the sonographic main lobar fissure (MLF). The sonographic MLF is a hyper-echoic landmark used by sonographers of the right upper quadrant. Found in approximately 70% of people, there is little consensus on what the sonographic MLF is anatomically. This structure appears to be related to the main portal fissure (aka principal plane of the liver or principal hepatic fissure), initially described by anatomists and surgeons as in intrahepatic division along the middle hepatic vein which in essence divides the territories of the left and right hepatic arteries and biliary systems. By exploring the relationship between the main portal fissure and the sonographic MLF in cadaveric livers ex vivo, the data suggest the sonographic MLF is actually an extrahepatic structure that parallels the rim of the main portal fissure. The authors recommend that this structure be renamed the "sonographic cystic pedicle," which includes the cystic duct and ensheathing fat and blood vessels. In the context of the redefined underlying anatomy, the absence of the sonographic cystic pedicle due to anatomic variation may serve an important clinical role in predicting complications from difficult laparoscopic cholecystectomies and is deserving of future study.

Anatomical variations in the pattern of the right hepatic veins draining the posterior segment of the right lobe of the liver

BACKGROUND

The pattern of drainage in the right posterior lobe of liver varies considerably. The knowledge of this variation is very important while performing various surgeries on the right posterior lobe.

AIM

A study was conducted to see the variations in the pattern of drainage of posterior segment of the right lobe of liver. The aim was to see the variations of right hepatic vein and small accessory hepatic veins draining the posterior segment, the presence of which led to modifications in drainage of posterior segment.

MATERIAL AND METHODS

Sixty formalin fixed adult human liver specimens were dissected manually.

RESULTS

According to the pattern of drainage of tributaries of right hepatic vein, the right hepatic vein was classified into type I, type II, type III and type IV. According to presence of inferior right hepatic vein, three types of drainage of posterior lobe were seen: Type I, (76.36%) right hepatic vein was large, draining wide area of posterior segment. A small inferior right hepatic vein drained the small area of posterior segment. In Type II, (19.92%) both right hepatic and inferior right hepatic veins were medium sized draining the posteroinferior segment of the right lobe concomitantly. In Type III, (32%) accessory veins, the middle right hepatic vein drained the posterosuperior (VII) as well as the posteroinferior (VI) segment. In one specimen, there were numerous middle right hepatic veins draining the right posterior segment. The knowledge of anatomic relationship of veins draining right lobe, is important in performing right posterior segmentectomy.

CONCLUSION

For safe resection of the liver, the complex anatomy of the distribution of the tributaries of the right hepatic vein and the accessory veins have to be studied prior to any surgery done on liver.

Three-dimensional volumetry in 107 normal livers reveals clinically relevant inter-segment variation in size

BACKGROUND

The anatomic resection of Couinaud's segments is one of the key techniques in liver surgery. However, the territories and volumes of the eight segments are not adequately assessed based on portal branching.

METHODS

Three-dimensional (3D) perfusion-based volumetry was performed in 107 normal livers. Based on Couinaud classification, the portal branches were identified and the volumes of each segment were calculated. The relationships between branching patterns of the portal veins and segmental volumes were assessed.

RESULTS

In descending order of volume, median volumes of segments VIII, VII, IV, V, III, VI, II and I were recorded. Segment VIII was the largest, accounting for a median of 26.1% (range: 11.1-38.0%) of total liver volume (TLV), whereas segments II and III each represented <10% of TLV. In 69.2% of subjects, the portal branches of segment V diverged from the trunk of the branches of segment VIII. No relationship was found between branching type and segment volume.

CONCLUSIONS

The territories and volumes of Couinaud's segments vary among segments, as well as among individuals. Detailed 3D volumetry is useful for preoperative evaluations of the dissection line and of future liver remnant volume in anatomic segmentectomy.

Variation or newly identified glissonian pedicles between the lateral and medial sections of the liver, using cadaver dissection

Purpose

Studies of liver anatomy have developed alongside clinical achievements, as these types of research complement each other. The aim of this study is to determine whether or not the portal vein branches (P4d) in 'Nagino's trisectionectomy' exist, and to examine their characteristics using cadaver dissection.

Methods

From April 2012 to July 2012, 31 adult cadavers were delicately dissected. We defined a 'NewGP' as an extra glissonian pedicle (GP) other than the traditional GPs that supply segments II, III, IVa, and IVb in the ordinary direction, and anatomically located superior to the umbilical fissure (UF).

Results

We identified 'NewGPs' based on the UF and UF vein. The incidence of 'NewGPs' was 30/31 (96.8%). The diameter of the 'NewGPs' ranged from 3.5 to 5.6 mm, which was not significantly different from that of traditional GPs (II-, III-, or IV-GP), which have diameters ranging from 3.7 to 9.7 mm.

Conclusion

We think that the P4d in 'Nagino's trisectionectomy' correspond to the 'IVa NewGP' and the additional pedicle. We believe the clinical significance of the 'NewGP' is to complement the traditional II, III, IVa, and IVb pedicles in supplying the liver.

Liver function testing with nuclear medicine techniques is coming of age

Liver function is a broad term, as the organ participates in a multitude of different physiological and biochemical processes, including metabolic, synthetic, and detoxifying functions. However, it is the function of the hepatocyte that is central to sustaining normal life and dealing with disease states. When the liver begins to fail in severely ill patients, it forecasts a terminal outcome. However, unlike the glomerular filtration rate which clearly quantifies the key renal function, at most practice sites, there is no clinically available quantitative test for liver function. Although it is commonplace to assess indirect evidence of that function (by measuring blood levels of its end products and by-products) and to detect an acute injury (by following rising transaminases), a widely available test that would directly measure hepatocellular function is lacking. This article reviews current knowledge on liver function studies and focuses on those nuclear medicine tests available to study the whole liver and regional liver function. The clinical application driving these tests, prediction of remnant liver function after partial hepatectomy for primary liver malignancy or metastatic disease, is addressed here in detail. The test was recently validated for this specific application and was shown to be better than the current standard of practice (computed tomography volumetry), particularly in patients with hepatic comorbidities like cirrhosis, steatosis, or cholestasis. Furthermore, early assessment of regional liver function increase after preoperative portal vein embolization becomes possible with this technology. The limiting factor to a wider acceptance of this test is based on the lack of clinical software that would allow calculation of liver function parameters. This article provides information that enables a clinical nuclear medicine facility to provide this test using readily available equipment. Furthermore, it addresses emerging clinical applications that are under investigation.

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.

Ramification of Glisson's sheath peripheral branches and clinical implications in the era of local ablation therapy

PURPOSE

Classical anatomical resection does not always guarantee tumor-free margins when the tumor overrides traditional anatomical planes. Surgeons and interventionists frequently need to focus on the peripheral branches of Glisson's sheath in patients with poor hepatic reserves, particularly when the tumor is deep seated. The present study used anatomical liver dissection to investigate the spatial distribution of the branches of Glisson's sheath in each of four liver sectors.

METHODS

Sixty-four adult human liver specimens were dissected. The size and ramification patterns of Glisson's sheath in each sector were analyzed in terms of bilateral homology within two paramedian sectors and within two lateral sectors.

RESULTS

Each liver sector had a characteristic Glisson's sheath in terms of trunk shape and ramification pattern. The two paramedian sectors showed point symmetry. Most of the branches of the two paramedian sectors emerged from the top of a short stout trunk. Although the two paramedian sectors were similar in terms of basic configuration, the ramification axes were almost perpendicular to each other. Unlike the paramedian sectors, the two lateral sectors showed not much homology.

CONCLUSIONS

The peripheral branches of Glisson's sheath were generally longer (approximately 5 cm) and thicker than anticipated. Extirpation strategies should take into account that each liver sector has a characteristic Glisson's sheath ramification pattern.

Reappraisal of Right Portal Segmental Ramification Based on 3-dimensional Volume Rendering of Computed Tomography During Arterial Portography

OBJECTIVE

To investigate and describe the segmental ramification patterns of the right portal vein (RPV) according to the Couinaud system.

MATERIALS AND METHODS

Between February 2004 and June 2005, 127 patients with hepatic tumors underwent computed tomography during arterial portography with a 16-slice multidetector computed tomography. The final analysis included 90 patients without RPV thrombosis or obvious vascular distortion. The ramification patterns of RPV were verified by 3-dimensional portograms using volume-rendering technique.

RESULTS

Seventy-five patients (83.3%) had bifurcation of the main portal vein, 12 (13.3%) had trifurcation, and 3 (3.3%) had the right posterior portal vein (RPPV) arising from main portal vein. A total of 5 segmental types and 3 subsegmental subgroups of RPV ramification patterns were clarified: type I, the classic ramification pattern with right anterior portal vein (RAPV) branching to S8/S5 and RPPV branching to S7/S6 (63; 70%); II, two separate segmental branches to S7 and S6 without a definite main stem of RPPV (18; 20%); III, "whisk-like" ramification pattern of RPV (2; 2.2%); IV, RAPV branching to S8 alone and RPPV to S5, S6, and S7, consecutively (5; 5.6%); and V, RPV first branching to S8/S5 and then to S7/S6 after a common path (2; 2.2%); subgroup a with dorsocranially directed branches arising from P8 and supplying S8 posterior to the right hepatic vein (28; 31.1%); subgroup b with RPPV branching to the dorsal part of S5 (11; 12.2%); and subgroup a + b, combination of the aforementioned 2 subgroups (45; 50%). In most patients, RAPV had dorsocranially directed branches posterior to the right hepatic vein (73; 81.1%), and RPPV gave off branches to the dorsal part of S5 (56; 62.2%).

CONCLUSIONS

Recognition of these ramification patterns could be helpful for more accurate anatomical resection of right hemiliver and preoperative planning, although some variants are present.

Prevalence and Types of Main and Right Portal Vein Branching Variations on MDCT

OBJECTIVE

Our objective was to investigate the prevalence of variant main and right portal vein ramification in a large group of patients.

SUBJECTS AND METHODS

The study group consisted of 200 patients who underwent consecutive contrast-enhanced abdominal CT examinations performed with an 8-MDCT scanner. Two observers evaluated both thin axial sections and 3D maximum-intensity-projection and volume-rendered images for branching patterns of the main and right portal veins.

RESULTS

Conventional main portal vein anatomy was present in 64.5% of the patients. In 9.5% of the patients, the main portal vein trifurcated into the left portal and right anterior and posterior portal veins. In 23.5% of the patients, the main portal vein divided into a common left portal vein-right anterior portal vein trunk and the right posterior portal vein. Three patients (1.5%) had miscellaneous variations. Twenty-two (16.8%) of 131 patients with conventional main portal vein branching had variant right portal vein branching, most of which was a trifurcation, followed by an abnormally proximal origin of the segment VII vein from the right portal vein.

CONCLUSION

Variant main portal vein branching seems to be very frequent. Common right anterior portal vein-left portal vein trunk is far more common than trifurcation. Although less frequent, variations also occur in right portal vein branching.

Feasibility of bisegmentectomy 7-8 is independent of the presence of a large inferior right hepatic vein

BACKGROUND

Right superior liver resection or bisegmentectomy 7-8 is defined as the anatomical removal of segments 7 and 8 of the liver. According to recent reports, this type of resection requires the presence of a large accessory right inferior hepatic vein to drain the remaining segment 6. However, anatomic studies have shown that segment 6 has multiple veins presenting several anastomosis with the surrounding hepatic veins. Therefore, the maintenance of the veins from segment 5 that ultimately drain into the middle hepatic vein can be enough to assure venous drainage of both segments.

METHODS

Describe an alternative technique for bisegmentectomy 7-8 using intrahepatic glissonian access in patients with absence of a large inferior right hepatic vein.

RESULTS

The technique was successfully performed in four consecutive patients without immediate or long-term venous or venous related complications.

CONCLUSIONS

Bisegmentectomy 7-8 may increase resectability rate in patients with bilateral lesions and may also enhance the opportunity to perform repeated resections in cases of tumor recurrence. Our study confirms the anatomical assumption that bisegmentectomy 7-8 did not result in segmental outflow block even in the absence of a thick inferior right hepatic vein and therefore should be performed more often than reported so far. The absence of this vein should not be a straightforward indication for right hepatectomy in cases where a liver-sparing procedure such as bisegmentectomy 7-8 can be safely employed.

Main accessory sulcus of the liver

It has been proposed that the superficial part of the portal fissures weakens the surface hepatic parenchyma, allowing the development of accessory sulci caused by diaphragmatic pressure. To evaluate the relationship of the sulci in the antero-superior surface of the right liver with the right portal fissure, macroscopic post mortem examination of 85 livers was carried out and radio-opaque resins were injected into the portal and hepatic venous systems to obtain vascular casts. After formalin fixation, the 85 livers also underwent CT and MR scans and 3D image elaboration. Diaphragmatic sulci were found in 32 cases. We studied the sulci located in the right liver, i.e., those that lay to the right of the line of Cantlie. They were found in 28 instances and in 16 cases they were multiple. In the livers with a single sulcus, it extended between the anterior and right surfaces of the right liver and showed a curved course downward and forward, toward the inferior margin. In the cases with multiple sulci, one sulcus always showed a course similar to that of the single sulci. The 28 sulci, with similar position and course, showed variable characteristics (mean length=7.6 +/- 2.7 cm, mean width=0.8 +/- 0.7 cm, mean depth=1.4 +/- 0.8 cm). Both radiological images and corrosion casts showed a correspondence between these sulci and the right hepatic vein and the right portal fissure in 71% of cases. These sulci may represent the variable expression (cranial, intermediate, or caudal portions) of a potential sulcus, the main accessory sulcus (MAS), that develops along a theoretically predictable course corresponding to the superficial part of the right portal fissure. The high prevalence of location of the MAS at the level of the upper part of the right portal fissure can be ascribed to the presence at this level of the watershed between the roots of the tributaries of the hepatic veins coming from segments VIII and VII, draining respectively into the middle and right hepatic veins. Thus, the coexistence of the two portal and hepatic venous boundaries may represent a further predisposition to the effects of diaphragmatic pressure. The MAS may represent a marking for the right portal fissure, and hence a superficial reference for the deep course of the right hepatic vein.

Limitations and pitfalls of Couinaud's segmentation of the liver in transaxial Imaging

The segmental anatomy of the human liver has become a matter of increasing interest to the radiologist, especially in view of the need for an accurate preoperative localization of focal hepatic lesions. In this review article first an overview of the different classical concepts for delineating segmental and subsegmental anatomy on US, transaxial CT, and MR images is given. Essentially, these procedures are based on Couinaud's concept of three vertical planes that divide the liver into four segments and of a transverse scissura that further subdivides the segments into two subsegments each. In a second part, the limitations of these methods are delineated and discussed with the conclusion that if exact preoperative localization of hepatic lesions is needed, tumor must be located relative to the avascular planes between the different portal territories.

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.

Configurations of the segmental and subsegmental bronchi and arteries in the right upper lobe of the human lung with special reference to their concomitant relations and double subsegmental arterial supply

The basic, concomitant topographical relation between the segmental bronchus and artery shows derived figures in the dorsolateral part of the cranial portion of the mammalian lung, especially in humans. However, the pulmonary arterial supply has not been investigated well in the subsegmental level, even in humans. One or two subsegments of S2 received a double arterial supply from both the superior and inferior pulmonary trunks in 39.8% of the right upper lobes of 194 human lung dissections, whereas 20.6% did so in S3, although the latter cases were limited to one of the two subsegments. Moreover, we found several arterial patterns that were significantly frequently observed in a specific group of the bronchial tree in S2 and/or S3. Invasion of an additional artery of inferior trunk origin seemed to happen at the same time in both segments even without complementary territorial relations with the essential segmental artery of the superior trunk origin. S2 and S3 in the human right lung seemed to be the best fields for reconsideration of the basic rules in the lung segment system in mammals as a result of their having the largest sets of variations. We speculate that the discrepancy between the bronchial and arterial ramification patterns, which was frequently found in S2 and S3, is a result of a hypothetical secondary increase of the comparative volume of this area in evolution and/or development of the lung.

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

The configuration of the right portion of the caudate lobe (CL), and especially the exact location of its right margin, remains obscure. This study aimed to identify this right margin according to reliable landmarks suitable for use during clinical examinations and surgery: (1) the bifurcation of the right portal vein, (2) the end of the right hepatic vein, and (3) the notch on the gallbladder fossa. The plane defined by these three landmarks is called the right paracaval plane. Dissection of 55 livers demonstrated that the entire CL was usually contained within the left half of the specimen after cutting along the right paracaval plane (Type A: 65.4%, 36/55). However, its right portion sometimes extended beyond this plane into the right half of the liver (34.6%, 19/55), forming one or two islands when viewed from the paracaval plane (Types B and C). We found two separate marginal configurations among the 19 rightward extensions of the paracaval portion: a tree-like, deep protrusion (11/19) and a relatively smooth border (8/19). The present results suggest the existence of reliable landmarks that will allow a right-side limit for surgical resection of the CL to be established: (1) the right paracaval plane (60% reliability), (2) 10 mm to the right of the plane, including the terminal of the right hepatic vein (80% reliability), and (3) the widest margin, including the 30 mm to the right of the right paracaval plane, the right side running along the inferior vena cava, and the diaphragmatic surface around the end portions of the three main hepatic veins (100% reliability).