Configuration of hepatic veins in the right surgical lobe of the human liver with special reference to their complementary territorial relationships: morphometric analysis of controlled specimens with clearly defined portal segmentation

Venous drainage map of the liver for complex hepatobiliary surgery and liver transplantation

BACKGROUND

Inflow and outflow patency of the liver parenchyma is required to maximize the metabolic function of the liver. However, the definition and distribution of hepatic venous drainage regions has yet to be reported. The aim of this study was to define major hepatic venous tributaries and investigate the mean drainage volume of each territory.

METHODS

Three-dimensional (3D) simulations from the livers of 100 healthy donors were reviewed for living donor liver transplantation to determine the distribution of the significant hepatic venous tributaries and the drainage patterns of each segment.

RESULTS

The left hepatic vein (LHV), middle hepatic vein (MHV), and right hepatic vein (RHV) contributed a mean drainage of 20.7%, 32.7%, and 39.6% of the entire liver, respectively. Accessory hepatic veins accounted for remaining 7.0%. The middle right hepatic vein (MRHV) and inferior right hepatic vein (IRHV) accounted for a mean total drainage of 8.0% and 10.6%, respectively, when they present. In addition, major tributaries of hepatic veins were clearly detected, and their typical distributions were described.

CONCLUSIONS

Knowledge of hepatic venous territories is necessary for complex hepatobiliary surgery. This "venous drainage map" may provide useful information for complex liver surgery and transplantation.

Morphometrical study of arteries and veins in the human sheet-like muscles (pectoralis major, latissimus dorsi, gluteus maximus and trapezius) with special reference to a paradoxical venous merging pattern of the trapezius

The trapezius is one of the critical targets of physical therapy for shoulder functional disorder because this muscle plays a great role in fixation and elevation of the shoulder. Trapezius (n = 63), latissimus dorsi (n = 5), pectoralis major (n = 7) and gluteus maximus (n = 7) muscles were obtained from 43 donated cadavers, and vascular morphologies were compared. An artery without a concomitant vein was found in 35 of 63 trapezius muscles. Moreover, twice as many venous merging sites as arterial branching sites were present in the trapezius. Notably, peripheral or distal venous tributaries were larger in caliber than the proximally located vein in 6.2% of all 404 venous merging sites in the trapezius. Moreover, similar paradoxical venous merging, in which tributaries were relatively thicker than drainage capacity of the venous trunk after merging according to Poisueille's law (peripheral or distal thickness >0.85 x proximal thickness), was observed in 39.1% (158 of 404 merging sites) in the trapezius, compared to 8-9% in the other 3 muscles. Given this vascular morphology, trapezius muscle seems likely to frequently display venous blood retention. Interestingly, venous valves were not observed in the trapezius, compared to 1-7 valves per one of the other 3 muscles. Abundant venous mergings without valves might form a venous network acting as a reservoir. Therefore, for the trapezius, collateral venous routes such as the external vertebral plexus are essential to provide additional peripheral drainage. However, sufficient muscle-pump function does not seem to be expected for trapezius muscle, given the venous courses parallel to muscle fibers.

Arterial supply and biliary drainage of the dorsal liver: a dissection study using controlled specimens

Liver surgeons favor using the entity called the 'dorsal liver' (i.e. the caudate lobe and other paracavally located liver parenchyme of segments 7 and 8). According to minute dissection of 48 livers, we describe the territories of the left/right portal veins, hepatic ducts and hepatic arteries in the dorsal liver. In the caudate lobe, the right hepatic artery, rather than the left hepatic artery (23/48 vs 19/48 for right vs left, respectively), tended to supply the 'left' portal vein territory. Similarly, paradoxical drainage patterns, such as the right hepatic duct draining the left portal vein territory, were found in seven of 48 livers. In the territory of the hilar bifurcation, right hepatic artery dominance was also evident and various bile drainage patterns were found. These included double drainage by the bilateral hepatic ducts (3/48) and drainage into the confluence of bilateral ducts (6/48). In contrast, the arterial supply and biliary drainage of the paracavally located parenchyme of segments 7 and 8 usually depended on the proper segmental arteries and ducts and their variations were within the range of those found in other parts of the right lobe. Therefore, the dorsal liver concept may not be anatomical but, rather, simply aimed at usefulness in surgery. Nevertheless, clear subdivision of the caudate lobe according to biliary drainage and/or arterial supply seemed difficult because of the paradoxical relatioships among the portal vein, hepatic artery and bile duct. Consequently, the present results support extended surgery based on the dorsal liver concept for carcinomas involving the caudate lobe.

Right lobe living donor liver transplantation-addressing the middle hepatic vein controversy

OBJECTIVE

To describe our approach in the decision-making for taking the middle hepatic vein with the graft or leaving it with the remnant liver in right lobe live donor liver transplantation.

SUMMARY BACKGROUND DATA

Right lobe living donor liver transplantation has been successfully performed. However, the extent of donor hepatectomy is still a subject of debate and the main considerations in the decision making are graft functional adequacy and donor safety.

METHODS

An algorithm based on donor-recipient body weight ratio, right lobe-to-recipient standard liver volume estimate, and donor hepatic venous anatomy was used to decide the extent of donor hepatectomy. This algorithm was applied in 25 living donor liver transplant operations performed between January 1999 and January 2002. In grafts taken without the middle hepatic vein, anterior segment tributaries draining into it were not reconstructed. Outcomes between right lobe liver transplants with (Group I) and without (Group II) the middle hepatic vein were compared.

RESULTS

Ten grafts included the middle hepatic vein and 15 did not. The mean graft to recipient standard liver volume ratio was 58% and 64% in Groups I and II, respectively, and the difference was not statistically significant. Donors from both groups had comparable recovery, with 2 complications, 1 from each group, requiring a percutaneous drainage procedure. The recipient outcomes were, likewise, comparable and there was 1 case of structural outflow obstruction in Group I, which required venoangioplasty and stenting. There were 2 recipient mortalities, 1 due to a biliary complication and the other to recurrent hepatitis C. Another patient required retransplantation for secondary biliary cirrhosis. The overall actuarial graft and patient survival rates are 84% and 96%, respectively, at a median follow-up of 16 months.

CONCLUSION

Based on certain preoperative criteria, a right lobe graft can be taken with or without the middle hepatic vein with equally successful outcomes in both the donors and recipients. The decision, therefore, of the extent of right lobe donor hepatectomy should be tailored to the particular conditions of each case.

Análise da segmentação venosa hepática através de moldes de resina

OBJETIVO: Aferir a independência da segmentação da drenagem venosa hepática, bem como a relação entre seus segmentos. MÉTODO: Foram utilizados trinta fígados humanos, analisados cuidadosamente para exclusão de possíveis rompimentos extra e intra-parenquimatosos. Foi injetada uma resina sintética (Resapol T-208) nas veias hepáticas direita, média e esquerda isoladamente, com diferentes cores, para identificação dos segmentos, utilizando-se a técnica de injeção-corrosão. Após a obtenção dos moldes, foi realizada a pesagem e a planimetria destes, em conjunto e separadamente. RESULTADOS: Foi observado que todos os moldes hepáticos apresentaram independência entre seus segmentos e que o segmento direito foi o maior (p=0,005). Ao correlacionar o peso do fígado com a proporção entre os segmentos, obteve-se um coeficiente de correlação de 0,023. CONCLUSÕES: Os segmentos das veias hepáticas são independentes entre si, ocorrendo preponderância do segmento venoso direito sobre os demais e o aumento do peso do fígado sem patologia corresponde a um aumento proporcional entre os seus segmentos.

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.

The minor hepatic veins: anatomy and classification

A detailed description of the distribution and drainage pattern of the minor hepatic veins is presented in this paper. A classification based on the segmentation of the liver divides these veins into four main groups: 1) veins of Segment I which includes the veins of the caudate lobe and the veins of the caudate process; 2) veins of Segment VI; 3) veins of Segment VII; and 4) veins of Segment IX. A knowledge of the anatomy of the minor hepatic veins becomes more clinically valuable as the number of complex dissections of the retrohepatic areas, hepatectomies. and hepatic transplantations grow.

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).