MIRALab Copyright © Information 1998

The Liver of the "Visible Man" J.H.D. Fasel1, P. Gingins2, P. Kalra2, N. Magnenat-Thalmann2, C. Baur3, J.F.Cuttat4, M. Muster5, P. Gailloud2 1

Department of Morphology, University Medical Center 2 3

4

MIRALab, University of Geneva

Swiss Federal Institute of Technology

Department of Digestive Surgery, University Hospital , Lausanne 5

Department of Radiology, University Hospital , Geneva Abstract:

Endoscopic surgery, also called minimally invasive surgery, is presumed to drastically reduce postoperative morbidity and thus to offer both human and economic benefits. For the surgeon, however, this approach leads to a number of gestural challenges that require extensive training to be mastered. In order to replace experimentation on animals and patients, we decided to develop a simulator for endoscopic surgery. To achieve this goal, a firm step was to develop a working prototype, a 'standard patient', on which the informatic and microengineering tools could be validated. We used the visible man dataset for this purpose. The external shape of the visible man's liver, his biliary passages and his extrahepatic portal system turned out to be fully within the standard pattern of normal anatomy. Anatomic variations were observed in the intrahepatic right portal vain, the hepatic veins and the arterial blood supply to the liver. Thus, the visible man dataset reveals itself to be very well suited for the simulation of minimally invasive surgical operation such as endoscopic cholecystectomy. Key words: Virtual surgery, endoscopic cholecystectomy, clinical anatomy, visible human project Introduction Derived from gyncological laparoscopy, endoscopic surgery (also called minimally invasive surgery or coelioscopy) has imposed itself since the end of the 80s as a new method, first in abdominal, then in thoracic surgery (McKeman, 1994). Il is presumed to drastically reduce postoperative morbidity and thus to offer both human and economic benefits. For the surgeon,

however, this approach involves a number of gestural challenges such as manipulation of new kinds and sizes of instruments, adaptation to a restricted field of view, bimanual ability with inversed eye-hand coordination and loss of tactile feedback. Thus, extensive training is required, which must avoid endangering living patients or risk ethical or political limitations in regard to animal experiments (Imbembo and Zucker, 1991; Altman, 1992; Wolfe et al., 1993; Hiatt et al., 1994). This can now be contemplated thanks to computerized virtual reality. The aim of our work is therefore to contribute to the elaboration of endoscopic surgery simulators. To achieve this goal, a first step was to develop a prototypic "standard patient", on which the informatic and microengineering tools could be validated. We used the visible man dataset to generate a simulation for endoscopic cholecystectomy. Since this was the first non-gynecological endoscopic procedure to be performed and therefore offers sufficient feedback (Filipi et al., 1991; McKernan, 1994), the present paper describes the hepato-biliary anatomy of the visible man. Materials and methods The visible man dataset is a part of the visible human project, initiated by the US National Library of Medicine (NML) (Ackermann, 1995). It comprises 1800 transverse cryosections at lmm intervals of a 39-year-old male subject, who had willed his body to the medical sciences. This collection of images corresponds to 15 gigabytes of data and is intended to offer a digital image library of volumetric data representing a complete normal human being. We used the cryosection slices 1458 to 1640 of the dataset. For the reconstruction of theliver we processed the data on a Silicon Graphics workstation using techniques described by Beylot et al. (1996), Geiger (1993), Kass et al. (1988), and summarized in Fig. 1. Results External Shape: The visible man's liver was of entirely classical external shape. It displayed the traditional four lobes (right, left, quadrate and caudate) and the H-shaped fossae and fissures on its inferior and posterior surfaces (Fig. 2). There was no bridge of liver parenchyma (pons hepatis) connecting the quadrate with the left lobe below the umbilical part of the left portal vein branch. Thus, the dorsal part of the fissure for the ligamentum tares hepatis was free, as was that for the ligamentum venosum. The groove for the inferior vena cava also did not display posterior parenchymateous connections. Biliary Tract The bile passages and the gallbladder are represented in Fig. 3. There were two hepatic ducts leaving the porta hepatis and forming the common hepatic duct. The gallbladder, free of calculi, emptied into the cystic duct, whose mucous membrane displayed the typical spiral shape. The cystie duct joined the common hepatic duct from the right side, just above the first part of the duodenum. The common bile duct passed behind the first part of the duodenum and the head of the pancreas. It united with the main pancreatic duct shortly before entering the descending part of the duodenum. No accessory biliary ducts were observed. Portal Vein:

The portal vein, formed by the superior mesenteric and the splenic veins, ascended to the right end of the liver hilum, where it bifurcated into its right and left branches (Fig. 4). The right portal vein gave rise to an anterior and a posterior trunk. The anterior trunk vascularized subsegment 8 (according to Couinaud, 1957, and Bismuth, 1982), whereas the posterior trunk first gave origin to the main branch to subsegment 5. The posterior trunk then bifurcated into two main branches, entering subsegments 6 and 7, respectively. The left portal vein, as usual, displayed a so-called transverse portion running to left within the liver hilum, and an umbilical portion within the fissure of the round ligament. The transverse part of the left portal vein gave origin to branches for the caudate lobe (=subsegment 1). At the site of the bend between the two portions of the left portal vein, the branch to subsegment 2 arose and immediately split into two branches. From the umbilical part of the left portal vein, and particularly from its end, a group of branches arose from its lateral and medial aspect, destinated to subsegment 3 and 4 respectively. In summary, the portal venous system in the visible man corresponded to the presumed standard distribution pattern, with exception of the main branch to subsegment 5 originating from the posterior (and not from the anterior) branch of the right portal vein. Hepatic Veins: The distribution of the hepatic veins in the visible man was also within the standard patterns. There were three principal trunks: the right, middle and left hepatic veins. The left and middle hepatic veins joined to form a short common trunk before emptying into the inferior vena cave. As far as the right hepatic vein was concerned, however, there were two large accessory right hepatic veins: a middle and an inferior one (Fig. 5). Arterial Blood Supply : The arterial blood supply to the liver, as far as it may be determinded on non-injected whole body cryosections, originated from the coeliac trunk by means of a common hepatic artery (Fig. 6). This latter bifurcated into its right and left branches medial to the portal vein. The right hepatic artery, after having immediately given rise to the gastroduodenal artery, crossed anteriorly to the common bile duct and then coursed posterior to the cystic duct. The left hepatic artery coursed upwards far medial within the lesser omentum, gave rise to an accessory left gastric artery and entered the liver hilum in the region of transition between transverse and umbilical portions of the left portal vein. Discussion The external shape of the visible man's liver, the biliary passages and the extrahepatic portal venous system revealed to be fully within the standard pattern of normal anatomy. The intrahepatic part of the portal venous system also corresponded to the presumed most frequent distribution pattern, as far as the left hemiliver was concerned (Gens, 1955; Couinaud, 1957; Healey, 1970; Couinaud, 1981) . The right portal vein gave rise to an anterior and a posterior branch presumed to vascularize the right anterior and the right posterior liver segments respectively (Goldsmith and Woodburne, 1957; Elias and Sherrick, 1969). In the visible man's liver, however, the inferior part of the right anterior segment (subsegment 5 according to Couinaud, 1957, and Bismuth, 1982) was vascularized by a main branch arising from the posterior trunk of the right portal vain very briefly after the origin of the anterior trunk destinated to subsegment 8 (Fig. 4). This behaviour may be considered as a variation (not an anomaly). But,

astonishingly enough, there is no complete accordance with regard to what is the most frequent distribution pattern of the portal vein even at the second generation branch level, and this despite the numerous investigations made (Rex, 1888; Melnikoff, 1924; Hjortsjö, 1951; Elias and Petty, 1952; Healy and Schroy, 1953; Gans, 1955; Couinaud, 1957). With regard to the major hepatic veins, the distribution pattern observed in the visible man corresponded to the prevailing pattern of branching described by Healey (1970), Masselot and Leborgne (1978) and Appel and Loeweneck (1987). As far as the right hepatic vein was concerned, however, two major accessory veins were observed (Fig. 5). According to Masselot and Leborgne (1978) they can be called middle and inferior accessory right retrohepatic veins. The frequency of these veins has been reported to be about 10% for the former and about 20% for the later (Masselot and Leborgne, 1978). These accessory right hepatic veins take over much of the drainage from the right hepatic vein proper. Concerning the arterial blood supply to the liver, the identification of the small vessels near the gallbladder and in the region of the liver hilum was not easy. The vascular pattern, as determined with this reservation, was an unusual one. First, the bifurcation of the common hepatic artery occurred medial to the portal vein. According to VanDamme and Bonte (1990), this is the case in about 6% of individuals without aberrant hepatic arteries. In the visible man, the right hepatic artery then crossed the common bile duct anteriorly. This pattern has been reported by Adachi (1928) and Michels (1955) with a frequency of about 3% in their material. Benson and Page (1976) reported an overall frequency of about 20% for right hepatic or cystic arteries crossing the common hepatic or common bile duel anteriorly. No indication is given for the sole right hepatic artery crossing anteriorly the common bile duct. Scott-Connor and Hall (1992) suggested an occurrence of about 18% for arteries lying anterior to the cystic duct, whereas Hugh et al. (1992) found a cystic artery running ventral to the common bile duct in 6% of their patients during laparoscopic cholecystectomy. With regard to the surgeons' training intended by the present study, the unusual arrangement observed in the visible man is welcome, since it demonstrates a variation that could lead to unexpected bleeding during cholecystectomy. The right hepatic artery lying ventral to the common bile duct will surprise the surgeon and challenge his capacity for adequate reaction. In conclusion, the visible man dataset appears to be very well suited for the simulation of minimally invasive surgical procedures such as endoscopic cholecystectomy. References Ackermann, M.J. 1995 The visible human project. http://www.nlm.nih.gov/research/visible/~ visible_human. Adachi, B. 1928 Des Arteriensystem der Japaner. Vol. Il. Kyoto: Verlag der KaiserlichJapanischen Universität, pp. 49 (fig. 30), 51-52. Altman, L.K. 1992 Surgical injuries lead to new rule. New York Times, 14.06.1992 Appel, M. and H. Loeweneck 1987 Verlauf und Mündungen der grossen Lebervenen zu Leitstrukturen an der Leberoberfläche. Chirurg, 58:243-247. Benson, E.A. and R.E. Page 1976 A practical reappraisal of the anatomy of the extrahepatic bile ducts and arteries. Br. J. Surg., 63:853-88O.

Beylot, P., P. Gingins, P. Kalra, N. Magnenat Thalmann, W. Maurel, D. Thalmann, and J. Fasel 1996 3D interactive topological modeling using visible human dataset. Eurographics, 15:C33C44. Bismuth, H. 1982 Surgical anatomy and anatomical surgery of the liver. World J. Surg., 6:3-9. Couinaud, C. 1957 Le foie. Etudes anatomiques et chirurgicales. Paris: Masson, pp. 71-74. Couinaud, C. 1981 Controlled hepatectomies and exposure of the intrahepatic bile ducts. Paris: Couinaud, pp. 10-14. Elias, H. and D. Petty 1952 Gross anatomy of the blood vessels and ducts within the human liver. Am. J. Anat., 90:59-111. Elias, H. and J.C. Sherrick 1969 Morphology of the liver. New York: Academic Press, pp. 268270, 281. Filipi, C.J., R.J. Fitzgibbons, G.M. Salerno 1991 Historical review: Diagnostic laparascopy to laparoscopic cholecystectomy and beyond. In: Zucker, K.A. (ed). Surgical laparascopy. St. Louis, Missouri: Quality Medical Publishing, pp. 3-21. Gans, H. 1955 Introduction to hepatic surgery. Amsterdam: Elsevier, pp. 51-60. Geiger, B. 1993 Three dimensional modeling of human organs and its application to diagnosis and surgical planning. Ph.D. Thesis, INRIA, France. Goldsmith, N.A. and R.T. Woodbume 1957 The surgical anatomy pertaining to liver resection. Surg. Gynecol. Obstet., 105:310-318. Healey, J.E. 1970 Vascular anatomy of the liver, Ann. N.Y. Acad. Sci., 170:8-17. Healey, J.E. and P. Schroy 1953 Anatomy of the biliary ducts within the human liver. Arch. Surg., 66:599-616. Hiatt, J.R., J.M. Sackier, G. Berci, N. Paz-Partlow 1994 The place of laparoscopy in modern surgical training. In: Steichen, F.M. and R. Welter (eds) Minimally invasive surgery and new technology. St. Louis, Missouri: Quality Medical Publishing, pp. 37-39. Hjortsjö, C.H. 1951 The topography of the intrahepatic duct systems. Acta Anat., 11:599-615. Hugh, T.B., M.D. Kelly, and B. Li 1992 Laparoscopic anatomy of the cystie artery. Am. J.Surg., 163:593-595. Imbembo, A.L. and K.A. Zucker 1991 Training for laparoscopie surgery and credentialing. In: Zucker, K.A. (ed) Surgical laparascopy. St. Louis, Missouri: Quality Medical Publishing, pp. 343-350. Kass, M., A. Witkin, and D. Terzopoulos 1988 Snakes: active contour models. Int. J. Comput.Vis., 1:321-331. Masselot, R. and J. Leborgne 1978 Etude anatomique des veines sus-hépatiques. Anat. Clin., 1:109-125.

McKeman, J.B. 1994 Essential concepts and skills in laparoscopic surgey. In: Steichen, F.M. and R. Welter (eds) Minimally invasive surgery and new technology. St. Louis, Missouri: Quality Medical Publishing, pp. 28-30. Melnikoff, A. 1924 Architektur der intrahepatischen Gefässe und der Gallenwege des Menschen. Z. Anat. Entw.Gesch., 70.411-465. Michels, N.A. 1955 Blood supply and anatomy of the upper abdominal organs. London: Pitman, pp. 152-154. Rex, H. 1888 Beiträge zur Morphologie der Sugerleber. Morphol. Jahrb., 14:517-616. Scott-Conner, C.E.H. and T.J. Hall 1992 Variant arterial anatomy in laparoscopic cholecystectomy. Am. J. Surg., 163:590-592. VanDamme, J.P. and J. Bonte 1990 Vascular anatomy in abdominal surgery. Stuttgart: Thieme, pp. 7-20. Wolfe, B.M., Z. Szabo, M.E. Moran, P. Chan, J.G. Hunter 1993 Training for minimallyinvasive surgery: need for surgical skills. Surg. Endosc. 7:93-95.

(a)Visible Male Data: Cryosections

(b)Preprocessing:Filtering, Cropping, Scaling, Filpping

(c)Labeling: Interpretation, 2D contouring

(d) 3D Reconstruction Fig. 1. Surface modeling process.

(a)

(b) Fig. 2. External shape of the visible man's liver. a Frontal view, b Left postero-lateral view. 1 Right lobe, 2 Left lobe, 3 Quadrate lobe, 4 Caudate lobe, 5 Gallbladder fosse, 6 Fissure of the teres ligament, 7 Fissure of the venous ligament, 8 Groove for the inferior vena cave.

Fig. 3. The gallbladder and biliary ducts. Frontal view. 1 Right hepatic duct, 2 Left hepatic duct, 3 Common hepatic duct, 4 Gallbladder with fundus (a), body (b) and neck (c); 5 Cystic duct; 6 Common bile duct.

Fig. 4. The portal vein. View from above and right. Note the origin of the branch to subsegment 5 from P (instead of A). P Portal vein, T Left portal vain, transverse portion, U Left portal vein, umbilical portion, R right portal vein, A Anterior branch of the right portal vein, P Posterior branch of the right portal vein, 1-8 main branches to the corresponding subsegments (according to Couinaud, 1957)

Fig. 5. The hepatic veins. Right antero-lateral view. Note the two accessory right hepaticveins. 1 left hepatic vein, 2 middle hepatic vein, 3 right hepatic vein, 4 middle accessory right hepatic vein, 5 inferior accessory right hepatic vein, 6 inferior vena cava

Fig. 6. The arterial blood supply to the visible man's liver. Frontal view with slight superior and right angulation and the biliary system also displayed. Observe the right hepatic artery (9)crossing the common bile duct ventrally. 1 Aorta, 2 superior mesenteric artery, 3 coeliac trunk, 4 left gastric artery, 5 splenic artery, 6 common hepatic artery, 7 left hepatic artery, 8 gastroduodenal artery, 9 right hepatic artery, 10 cystic artery. [1] To be published in journal Clinical Anatomy.