Anatomy of the right anterosuperior area (segment 8) of the liver: evaluation with helical CT during arterial portography

Liver Anatomy 2.0 Quiz: Test Your Knowledge

The liver is one the largest organs in the abdomen and the most frequent site of metastases for gastrointestinal tumors. Surgery on this complex and highly vascularized organ can be associated with high morbidity even in experienced hands. A thorough understanding of liver anatomy is key to approaching liver surgery with confidence and preventing complications. The aim of this quiz is to provide an active learning tool for a comprehensive understanding of liver anatomy and its integration into clinical practice.

Augmented Reality Navigation Plus Indocyanine Green Fluorescence Imaging Can Accurately Guide Laparoscopic Anatomical Segment 8 Resection

BACKGROUND

Laparoscopic anatomical Segment 8 (S8) resection is a highly challenging hepatectomy. Augmented reality navigation (ARN), which could be combined with indocyanine green (ICG) fluorescence imaging, has been applied in various complex liver resections and may also be applied in laparoscopic anatomical S8 resection. However, no study has explored how to apply ARN plus ICG fluorescence imaging (ARN-FI) in laparoscopic anatomical S8 resection, or explored its accuracy.

PATIENTS AND METHODS

This study is a post hoc analysis that included 31 patients undergoing laparoscopic anatomical S8 resection from the clinical NaLLRFI trial, and the resected liver volume was measured in each patient. The perioperative parameters of safety and feasibility, as well as the accuracy analysis outcomes were compared.

RESULTS

There were 16 patients in the ARN-FI group and 15 patients underwent conventional laparoscopic hepatectomy without ARN or fluorescence imaging (non-ARN-FI group). There was no significant difference in baseline characteristics between the two groups. Compared with the non-ARN-FI group, the ARN-FI group had lower intraoperative bleeding (median 125 vs. 300 mL, P = 0.003). No significant difference was observed in other postoperative short-term outcomes. Accuracy analysis indicated that the actual resected liver volume (ARLV) in the ARN-FI group was more accurate.

CONCLUSIONS

ARN-FI was associated with less intraoperative bleeding and more accurate resection volume. These techniques may address existing challenges and provide rational guidance for laparoscopic anatomical S8 resection.

Study of the Intersegmental Veins Between S5 and S8 Based on 3D Reconstruction

BACKGROUND

Anatomic resection (AR) is a surgical method for treating hepatocellular carcinoma, and identifying intersegmental planes between segments 5 (S5) and 8 (S8) remains challenging. This study aims to find reliable intersegmental veins (IVs) between them as anatomical landmarks using 3D reconstruction analysis.

METHODS

We retrospectively evaluated 57 patients who underwent multidetector-row CT scans from September 2021 to January 2023. The portal vein watershed of S5 and S8 and hepatic veins were reconstructed using 3D reconstruction analysis software. We counted and analyzed the IVs running within the intersegmental plane between S5 and S8, examined their features, and analyzed the location of the junctions between IVs and middle hepatic veins (MHVs).

RESULTS

Among the 57 patients, 43 patients (75.4%) had IVs between S5 and S8. Most patients (81.4%) had a single IV joining the MHV, while 13.9% had two IVs, one joining the MHV and the other joining the right hepatic vein (RHV). The majority of IV-MHV junctions were found in the lower part of the MHVs. The most clearly identifiable junctions between the IVs and MHVs occurred slightly below the midpoint of the horizontal planes of the second hepatic portal and the center of the gallbladder bed.

CONCLUSION

Our study identified IVs between S5 and S8 in the liver as potential anatomical landmarks during AR for hepatocellular carcinoma surgery. We found three types of IVs and provided insights on how to locate their junctions with MHVs for easier surgical navigation. However, individual anatomical variations must be considered, and preoperative 3D reconstruction and personalized surgical planning are crucial for success. More research with larger sample sizes is needed to validate our findings and establish the clinical significance of these IVs as landmarks for AR.

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.

What is the optimal surgical treatment for hepatocellular carcinoma beyond the debate between anatomical versus non-anatomical resection?

The optimal type of hepatectomy for hepatocellular carcinoma (HCC)-anatomical or non-anatomical resection-remains controversial despite numerous comparative studies. There are common fundamental issues in published studies comparing anatomical resection with non-anatomical resection: (1) confounding by indication, (2) setting primary outcomes, and (3) a lack of a clear definition of non-anatomical resection. This degrades the quality of the comparison of the two types of surgery. To measure the therapeutic effect of hepatectomy, it is essential to understand the accumulated knowledge underlying these issues, such as the mechanism of hepatocellular carcinoma spread, tumor blood flow drainage theory, and the three patterns of hepatocellular carcinoma recurrence: (1) local intrahepatic metastasis, (2) systemic metastasis, and (3) multicentric carcinogenesis recurrence. Based on evidence that the incidence of local intrahepatic metastasis was so low it was almost negligible, the therapeutic effect of anatomical resection on the oncological survival was determined to be similar to that of non-anatomical resection. Recent research progress demonstrating the clinical impact of subclinical dissemination of HCC after surgery may stimulate new debate on the optimal surgical treatment for HCC beyond the comparison of anatomical and non-anatomical resection.

Anatomical Versus Non-anatomical Resection for Hepatocellular Carcinoma, a Propensity-matched Analysis Between Taiwanese and Japanese Patients

BACKGROUND/AIM

The aim of the study was to compare the outcomes of anatomical resection (AR) versus non-anatomical resection (NAR) for Japanese and Taiwanese patients with single, resectable hepatocellular carcinoma (HCC).

PATIENTS AND METHODS

A propensity score matched (PSM) analysis was performed to compare the outcomes of the AR group to those of the NAR group. Tumor size <5 cm, T1 or T2 grade, without evidence of extrahepatic metastasis, invasion of portal or hepatic veins, or direct invasion of adjacent organs, were included in the study.

RESULTS

A total of 385 cases (Taiwanese 105, Japanese 280) were analyzed. After PSM, a total of 152 cases remain (Taiwan and Japan both 76 cases). Disease-free survival (DFS) and overall survival (OS) data were not significantly different between the two groups at 5 years follow-up.

CONCLUSION

AR of HCC in Japanese patients has a similar 5-year DFS and OS as NAR of HCC in Taiwanese patients.

Anatomy of the Right Anterior Sector of the Liver and Its Clinical Implications in Surgery

BACKGROUND

Surgery remains the gold standard both for delimited hepatocellular carcinoma by selective anatomic liver segentectomy and for colorectal liver metastases by parenchymal sparing liver resection. Right anterior sector (RAS) (segments V-VIII; Couinaud) is the largest and most difficult sector to operate on. A better knowledge of its segmentation could prevent postoperative remnant liver ischemia and its impacts on patient's survival.

METHODS

A literature search was conducted in PubMed for papers on anatomy and surgery of the right anterior sector.

RESULTS

Segmentation of the RAS depended of the anatomic variations of the third-order portal branches. Cranio-caudal segmentation was the most commonly found (50-53%), followed by ventro-dorsal (23-26%), trifurcation (13-20%), and quadrifurcation types (5-11%). Ventral and dorsal partial or total subsegmentectomy seemed accessible in 47 to 50% of patients, including bifurcation, trifurcation, and quadrifurcation types, and could spare up to 22% of the total liver volume. The RAS hepatic vein was present in 85-100% of the patients and could be used as a landmark between RAS dorsal and ventral part in 63% of patients. Reported overall morbidity rate of RAS subsegmentectomy ranged from 33 to 59% among studies with a postoperative major complication rate (Clavien-Dindo ≥ III) ranging around 18% and a biliary leakage rate from 16 to 21%. In-hospital reported mortality rate was low (0-3%), and results were comparable to "classic" liver resections. RAS subsegmentectomy remains a complex procedure; median operating time ranged from 253 to 520 min and median intraoperative blood loss reached 1255 ml.

CONCLUSION

Better knowledge of RAS anatomy could allow for parenchymal preservation by using subsegmentectomy of the RAS, selective or as a part of a major hepatectomy.

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.

Anatomical resection of hepatocellular carcinoma: A critical review of the procedure and its benefits on survival

Hepatocellular carcinoma (HCC) is the sixth most common type of cancer and the third most frequent cause of cancer-related death. Advances in preoperative assessment of HCC (e.g., imaging studies and liver function tests), surgical techniques, and postoperative care have improved the surgical outcomes and survival of patients who undergo hepatic resection for HCC. However, in the last 20 years, the long-term survival after hepatectomy has remained unsatisfactory owing to the high rates of local recurrence and multicentric occurrence. Anatomical liver resection (AR) was introduced in the 1980s. Although several studies have revealed tangible benefits of AR for HCC, these benefits are still debated. Because most HCCs occur in patients with liver cirrhosis and poor hepatic function, there are many factors that affect survival, including the surgical method. Nevertheless, many studies have documented the perioperative and long-term benefits of AR in various conditions. In this article, we review the results of several recently published, well-designed comparative studies of AR, to investigate whether AR provides real benefits on survival outcomes. We also discuss the potential pitfalls associated with this approach.

Study on the segmentation of the right anterior sector of the liver

BACKGROUND

The segmentation of the right anterior sector of the liver still is debatable due to the lack of an anatomic landmark of the boundary between Couinaud segments V and VIII (cranio-caudal segmentation). Some authors have proposed the concept of a ventro-dorsal segmentation. The aim of this study was to evaluate which concept of segmentation better reflects the anatomy.

METHODS

Using 3-dimensional computed tomography software, the ramification pattern of the right anterior portal vein was examined in 100 patients. A thick, hepatic, venous branch that passes through Couinaud segment VIII was termed V8, and its course was investigated using a virtual hepatectomy.

RESULTS

Regarding the anatomy of the portal vein in the right anterior sector, the cranio-caudal type was found in 53 patients, the ventro-dorsal type in 23 patients, and the trifurcation type in 13 patients. The remaining 11 patients had miscellaneous patterns of ramification. In the cranio-caudal type, the volume of the cranial segment was greater (P < .001) than that of the caudal segment. In the ventro-dorsal type, the volume of the ventral segment was greater (P = .007) than that of the dorsal segment. The V8 was identified in 81 of the 89 (91%) patients analyzed. The proportion of cases in which the V8 functioned as a landmark of the border between the ventral and dorsal segments was 63% (56/89 patients).

CONCLUSION

Regarding the segmentation of the right anterior sector of the liver, the cranio-caudal segmentation introduced by Couinaud is dominant (53%), while ventro-dorsal segmentation is less common (23%). Therefore, universalization of the concept of the ventro-dorsal segmentation is unrealistic.

Right posterior segment graft in living donor liver transplantation

AIM

Living donor liver transplantation (LDLT) is widely performed for end-stage liver disease. Liver volume is important for donor safety and recipient survival. In adult-to-adult LDLT, left lobe graft is frequently insufficient for the recipient, while right lobe graft carries a higher donor risk. The right posterior segment graft (RPSG) was introduced to increase donor selection options. However, only a few institutions have reported LDLT with an RPSG.

METHODS

In total, 587 adult recipients underwent LDLT at Kyoto University Hospital from 2001 to 2011. Here, we retrospectively report 14 LDLT with RPSG. All donors underwent volumetric analyses and detailed investigation of the hepatic vein (HV), portal vein (PV), hepatic artery (HA) and biliary duct (BD). Anatomical anomalies were detected in four donors' BD. The mean Model for End-Stage Liver Disease score was 22.6 ± 12.4 points. ABO blood groups were characterized as incompatible in three cases. The mean graft-to-recipient weight ratio was 0.897 ± 0.203.

RESULTS

Donors' postoperative courses were uneventful. To adjust diameters and lengths between grafts and recipients, dual anastomoses for PV reconstruction and graft interpositions for PV and HA reconstruction were required in one case each. HA thrombosis occurred in two cases and PV thrombosis in one. Biliary complications occurred in two cases. Though there was no significant difference in survival following RPSG versus other grafts, critical complications were observed in recipients.

CONCLUSION

The RPSG is a useful option in LDLT. However, careful consideration is required for RPSG harvest and LDLT performance, both before and during surgery.

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.

Concepts for Liver Segment Classification: Neither Old Ones nor New Ones, but a Comprehensive One

Concepts dealing with the subdivision of the human liver into independent vascular and biliary territories are applied routinely in radiological, surgical, and gastroenterological practice. Despite Couinaud's widely used eight-segments scheme, opinions on the issue differ considerably between authors. The aim of this article is to illustrate the scientific basis for understanding and harmonizing inconsistencies between seemingly contradictory observations. Possible clinical implications are addressed.

Liver blood supply after a modified Appleby procedure in classical and aberrant arterial anatomy

Reported here are two cases of a modified Appleby operation for borderline resectable ductal adenocarcinoma of the pancreatic body, in one of which a R0 distal resection was attended to by excision, not only of the celiac axis, but also of the common and left hepatic arteries in the presence of arterial anatomic variation Michels, type VIIIb. The possibility and avenues of the maintenance of the blood supply to the left hepatic lobe after surgical aggression of this kind are demonstrated employing computed tomography (CT) and 3-D CT angiography. Furthermore, both cases highlight all important worrisome aspects of pancreatic cancer resectability prediction.

Analysis of the caudate artery with three-dimensional imaging

BACKGROUND/PURPOSE

To date there have been only a few radiological studies of the caudate artery. This study aimed to precisely analyze the caudate artery as well as the relationship between the caudate arteries, the arterial plexus at the hilar plate, and the hilar bile duct.

METHODS

Reconstructed three-dimensional (3D) computed tomography images from 50 patients during hepatic arteriography were analyzed. The caudate arteries were classified as right branches (Irs) or left branches (Ils). The communicating artery (CA) was defined as the artery connecting the right, left, segmental, and common hepatic arteries.

RESULTS

The caudate artery was divided into 3 types: an independent branch (Type 1); the common tract formed by Ir and Il (Type 2); and an arterial branch from the CA (Type 3). The CA was recognized in 25 of 50 patients. There was a total of 65 arteries to the hilar bile duct observed in 40 patients, and 24 (37 %) of these 65 arteries to the hilar bile duct originated from the caudate artery or CA.

CONCLUSION

The caudate artery plays an important role not only in connecting the blood supply of the right and left livers but in the blood supply to the hilar bile duct.

Volumetry-based selection of right posterior sector grafts for adult living donor liver transplantation

To determine the feasibility of volumetric criteria without anatomic exclusion for the selection of right posterior sector (RPS) grafts for adult-to-adult living donor liver transplantation (LDLT), we reviewed and compared our transplant data for RPS grafts and right lobe (RL) grafts. Between January 2008 and September 2010, adult-to-adult LDLT was performed 65 times at our institute; 13 of the procedures (20%) were performed with RPS grafts [the posterior sector (PS) group], and 39 (60%) were performed with RL grafts (the RL group). The volumetry of the 13 RPS donor livers showed that the RPS volume was 39.8% ± 7.6% of the total liver volume. Ten of the 13 donors had to donate RPS grafts because the left liver volume was inadequate. All donor procedures were performed successfully, and all donors recovered from hepatectomy. However, longer operative times were required for the procurement of RPS grafts versus RL grafts (418 ± 40 versus 345 ± 48 minutes, P < 0.001). The postoperative recovery of liver function was smoother for the donors of the PS group versus the donors of the RL group. The RPS grafts had significantly smaller hepatic artery and bile duct openings than the RL grafts. All recipients with RPS grafts survived LDLT. No recipients experienced vascular graft complications or small-for-size graft dysfunction. There were no significant differences in the incidence of posttransplant complications between the donors and recipients of the PS and RL groups. The 3-year graft survival rates were favorable in both groups (100% in the PS group versus 91% in the RL group). In conclusion, the selection of RPS grafts by volume criteria is a feasible strategy for an adult-to-adult LDLT program.

Extended left hepatectomy of the left and middle hepatic venous drainage areas along the anterior fissure

BACKGROUND

Extended left hepatectomy including the middle hepatic vein (MHV) may potentially induce right paramedian sector congestion of the remnant liver.

METHODS

To prevent venous congestion in the right paramedian sector, we performed extended left hepatectomy including the left hemiliver and anterior segment, which drain into the MHV and left hepatic vein (LHV), for 15 patients.

RESULTS

In 11 of 15 patients (73%), temporary clamping of the common trunk of the MHV and LHV and the proper hepatic artery provided the anterior fissure. Regeneration rate of the middle segment was similar to that of the right lateral sector (10.8% vs 11.2%) on postoperative computed tomography (CT) after 3 months.

CONCLUSIONS

This procedure could represent a useful method for preventing postoperative venous congestion.

[Anatomy of the liver: what you need to know]

A precise knowledge of arterial, portal, hepatic and biliary anatomical variations is mandatory when a liver intervention is planned. However, only certain variations must be searched when a precise intervention is planned. The basic liver anatomy as well as the most relevant malformations will be precised.

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.

Relationship between right portal and biliary systems based on reclassification of the liver

BACKGROUND

Although the anatomy of the right portal and biliary systems and their interrelationships must be understood to safely and satisfactorily perform left-sided resection of hilar cholangiocarcinoma or right-lobe living donor liver transplantation, the anatomies of the right portal and biliary systems are extremely difficult to understand.

METHODS

A total of 60 patients with normal liver underwent computed tomography during both portography and cholangiography to evaluate relationships between the right biliary and portal systems based on reclassification of the liver to divide the right liver into 3 segments.

RESULTS

All ventral and posterior ducts constantly join medially to the anterior portal trunk. In contrast, some dorsal ducts join the ventral duct medially and others join the posterior duct lateral to the anterior trunk.

CONCLUSIONS

Reclassification of the liver to divide the right liver into 3 segments facilitates an understanding of relationships between the right portal and biliary systems.

Communicating arcade between the right and left hepatic arteries: evaluation with CT and angiography during temporary balloon occlusion of the right or left hepatic artery

PURPOSE

To evaluate prospectively the relationship between the arterial collateral system at the hepatic hilum and the blood supply to the hilar bile duct by using computed tomography (CT) and angiography during temporary balloon occlusion of the right or left hepatic artery.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained. The study included 13 patients with no lesions at the hepatic hilum (eight men and five women; age range, 41-78 years; mean, 65.8 years). After serial angiographic studies were performed for preoperative evaluation or transcatheter arterial chemoembolization, a 5.5-F catheter with an occlusion balloon was positioned in the right or left hepatic artery. Eleven patients underwent angiography of the left hepatic artery with temporary occlusion of the right hepatic artery, and two patients underwent angiography of the right hepatic artery with temporary occlusion of the left hepatic artery. In addition, 11 patients underwent single-level dynamic CT during hepatic arteriography (CTHA) with temporary occlusion of the right or left hepatic artery. The images from angiography and CTHA were interpreted by two authors who assessed the existence of the arterial communication and its branching points, location, and relationship to the hilar bile duct and caudate lobe.

RESULTS

During temporary occlusion of the right or left hepatic artery, the communicating arcade (CA) between the right and left hepatic arteries was immediately evident in all patients. On the left side, the CA originated from the segment IV artery in eight patients (62%) and from the left hepatic artery in five (38%). On the right side, the CA originated from the right anterior hepatic artery in six patients (46%), the right hepatic artery in two (15%), and both arteries in five (38%). The CA was extrahepatically located close to the hilar bile duct and forked into a few branches to the caudate lobe.

CONCLUSION

The CA may play an important role not only in the interlobar arterial collateral system but also in the blood supplies to the caudate lobe and hilar bile duct.

Proposal for a reclassification of liver based anatomy on portal ramifications

BACKGROUND

Portal branching patterns that differ from those previously described are occasionally encountered during liver surgery.

METHODS

A total of 60 patients with normal intrahepatic venous anatomy underwent helical computed tomography during arterial portography (CTAP). Next, 3 dimensional portograms were reconstructed to verify the locations of the portal veins. Portal branching patterns in the right hemiliver were assessed.

RESULTS

In all 60 patients examined, the right anterior portal vein bifurcated into the ventral and dorsal branches. In 42 (70%) of 60 patients, some branches arose from the right posterior portal trunk. Between 1 and 3 branches (mean 2.3 branches per patient) coursed cranially, between 2 and 5 branches (mean 3.2 branches per patient) coursed caudally, and between 1 and 2 branches (mean 1.3 branches per patient) coursed laterally.

CONCLUSIONS

We propose that the right liver should be divided into 3 segments, which are designated as the right anterior, middle, and posterior segments.

Relation between hepatic and portal veins in the right paramedian sector: proposal for anatomical reclassification of the liver

Although a right liver graft without a middle hepatic vein resulted in potential venous congestion in the right paramedian sector, the details of the hepatic venous distribution in the right paramedian sector have not been established. In this study, the ramification patterns of the hepatic veins draining the right anterosuperior segment (S8) and the relation between the hepatic and portal veins were assessed using multislice computed tomography in 44 patients without lesions in the liver. All 52 drainage veins of the ventral area of S8 joined the middle hepatic vein, and all 48 drainage veins of the dorsal area joined the right hepatic vein. The hepatic vein crossing between the ventral and dorsal areas was observed in each patient examined. Therefore, we propose a reclassification wherein the right paramedian sector is divided into ventral and dorsal segments. This new classification may contribute to the development of new and safer surgical procedures, including more limited resection and right lobe adult living donor liver transplantation to avoid graft congestion.

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.

Multi–Detector Row CT of Relevant Vascular Anatomy of the Surgical Plane in Split-Liver Transplantation

PURPOSE

To evaluate relevant arterial and venous anatomy of the hepatectomy plane lateral to segment IV by using multi-detector row computed tomography (CT) with respect to adult living related transplantation of the right lobe of the liver.

MATERIALS AND METHODS

In potential liver donors, 100 consecutive hepatic CT angiograms were obtained after intravenous bolus administration of 150-180 mL of nonionic contrast material. Arterial phase images (1.25-mm collimation, 7.5 mm/ 0.8-second table speed) were acquired after test dose injection. Portal phase images were acquired at 60 seconds (2.5-mm collimation, 15 mm/0.8-second table speed). Postprocessing depicted arterial, portal, and hepatic vein anatomy traversing the anticipated surgical hepatectomy plane to the right of the middle hepatic vein (MHV) and separating the right and left lobes of the liver. Two radiologists interpreted the images, and data were agreed on by consensus. Data collected included intrahepatic anatomy and origin of the artery and vein supplying segment IV; the venous drainage from segments V and VIII; and the presence, size, and distance from the right hepatic vein (RHV) confluence of accessory hepatic veins in the surgical plane.

RESULTS

Thirty-one donors had conventional hepatic vascular anatomy. Vessels that traversed the hepatectomy plane included the artery supplying segment IV in seven (7%) patients, dominant portal vein supply to segment IV from the right portal vein in two (2%) patients or from both right and left portal vein branches in three (3%) patients, segment VIII draining into the MHV in 67 (67%) patients or both the MHV and RHV in 18 (18%) patients (the major draining vein was >7 mm in diameter in 23%), segment V draining into the MHV in 10 (10%) patients, or both the MHV and RHV in 19 (19%) patients (the major draining vein from segment V was 7-10 mm in diameter in 70 patients, and larger than 10 mm in five). Forty-four accessory hepatic veins were identified in 40 patients; seven drained segment V, while the majority drained segments VI and VII. The mean diameter was 5.3 mm and 45% were larger than 6 mm. The average distance to the RHV-inferior vena cava confluence was 28.7 mm. Of 70 patients with drainage from segment V into RHV, 22 (31%) had an accessory RHV. However, atypical drainage into the MHV was noted in seven (70%) of 10 patients and into the MHV and RHV in 11 (58%) of 19 patients.

CONCLUSION

In the majority of potential donors, CT angiography depicted a wide range of vascular anatomic variations that traverse the hepatectomy plane.

Relationship between left biliary duct system and left portal vein: evaluation with three-dimensional portocholangiography

PURPOSE

To investigate the relationship between the left biliary duct system and the left portal vein by using in vivo analysis of the human liver with three-dimensional portocholangiography.

MATERIALS AND METHODS

Twenty-seven patients underwent helical computed tomography during both arterial portography and cholangiography. Three-dimensional portocholangiograms were reconstructed to evaluate the relationship between the left biliary duct system and the left portal vein, in particular the umbilical portion.

RESULTS

In 16 (59%) patients, segment II and III ducts united just above the umbilical portion or laterally to it, and the segment IV duct joined medially to the umbilical portion. In eight (30%) patients, segment III and IV ducts united medially to the umbilical portion and the segment II duct joined at a point close to the hepatic hilum. In three (11%) patients, three ducts from segments II-IV united at a position immediately medial to the umbilical portion.

CONCLUSION

Three types of left bile duct anatomy were seen in relation to the left portal vein.

Living donor liver transplantation in adults: vascular variants important in surgical planning for donors and recipients

OBJECTIVE

The purpose of our study was to explore the frequency with which surgically important hepatic vascular variants occur independently as well as in genetically related adult candidates for donation or receipt of a liver transplant.

MATERIALS AND METHODS

We conducted a retrospective study of 107 adult living donor liver transplant candidates. From this pool of candidates, 50 sets of close relatives were selected to undergo transplantation. As part of the preoperative evaluation, all underwent multidetector CT angiography for evaluation of arterial and venous anatomy. Nonionic IV contrast material (180 mL) was given at a rate of 5 mL/sec, and collimations of 1.25 and 2.50 mm were used for true arterial and portal hepatic venous phase scanning, respectively. Image processing included three-dimensional volume renderings and multiplanar reformations. Two radiologists assessed the prevalence of vascular variants that were important for surgical planning and execution.

RESULTS

We identified surgically important hepatic vascular variants in 70 (65%) of the 107 patients. A total of 129 variants were identified, of which 27 were important surgical considerations for recipients, 37 were important for donors, and 65 were important for both recipients (19 variants) and donors (46 variants). Of the 50 pairs of close relatives, 10 (20%) of the pairs were found to have the same hepatic vascular variant or one that was similar. However, when the pairs were set randomly, with no genetically related pairs included, similar variants were noted in 11 pairs (22%). The most common hepatic arterial variant in all candidates was an accessory right or left hepatic artery. The most common hepatic venous variant was an accessory right inferior hepatic vein.

CONCLUSION

We observed a high prevalence of surgically important vascular variants in living adult candidates for living liver transplant donation and receipt. Because of the frequent occurrence, similar variants are to be expected among these sets of patients, regardless of whether they are closely related.

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.