A new method of three-dimensional computer assisted reconstruction of the developing biliary tract

[Computerized three-dimensional reconstruction of the retrohepatic segment of inferior vena cava of a 20 mm human embryo]

The subdiaphragmatic venous drainage of the embryo is provided by the two caudal cardinal veins to which is added the subcardinal vein system, draining the mesonephros, the perispinal supracardinal veins and the umbilical and vitelline venous system. The anastomosis of certain segments of the embryonic venous structures and the disappearance of others are at the origin of the inferior vena cava. Since the 19th century, three-dimensional reconstruction of solid models from histological sections were developed. At present, the development of computerized three-dimensional reconstruction techniques allowed to operate a multitude of techniques of image processing and modeling in space. Three-dimensional reconstruction is a tool for teaching and research very useful in embryological studies because of the obvious difficulty of dissection and the necessity of introducing time as the fourth dimension in the study of organogenesis. This method represents a promising alternative compared to previous three-dimensional reconstruction techniques including Born technique. The aim of our work was to create a three-dimensional computer reconstruction of the retrohepatic segment of the inferior vena cava of a 20mm embryo from the embryo collection of Saints-Pères institute of anatomy (Paris Descartes university, Paris, France) to specify the path relative to the liver and initiate a series of computerized three-dimensional reconstruction that will follow the evolution of this segment of the inferior vena cava and this in a pedagogical and morphological research introducing the time as the fourth dimension.

[3D reconstruction of anterior internal vertebral venous plexus of a human fetus: a feasibility study]

Anterior internal vertebral venous plexus have been studied extensively due to their clinical importance in diseases of the spine and obstruction of the inferior vena cava. The aim of this feasibility study was to reconstruct in 3D the lower thoracic area of the anterior epidural space of a 69 mm (crown-rump) human fetus from the Rouvière Collection, circa 1927. Forty slices (spaced by 40 microm) at the level of the tenth and eleventh thoracic vertebrae, and their lower adjacent intervertebral discs, were reconstructed in 3D using the commercial software SURFdriver. In a preliminary study, we had found that the structures of the epidural space are already formed at this stage of development, and that they are comparable to the adult stage (2002). Reconstruction of the microscopic slices in 3D allowed to better visualize spatially the structures of the venous plexus and their anatomical relationships. This technique could be used as a complement to the classically used histological studies.

Three-dimensional computer-assisted reconstruction of ductal plate in the rat embryo (Carnegie stages 19-23)

In bile duct morphogenesis it has been established that the extrahepatic bile ducts in human originate from hepatic diverticulum while intrahepatic bile ducts arise from the ductal plate (DP), a network of primitive biliary epithelium that develops in the periportal connective tissue. The aim of this work was to reconstruct in rat embryos, stages 19-23, the three-dimensional (3D) distribution of the DP by means of a computer-assisted method. Six specimens, stages 19-23, fixed, dehydrated and paraffin-embedded, were submitted to serial histological sections and stained by hematoxylin-eosin and Heidenhain techniques. The images were directly digitalized with a CCD camera. The serial views were aligned anatomically by software and the data were analyzed following segmentation and thresholding. At stage 19, the DP was not yet organized. The periportal mesoderm (M) was gaining ground with some cords of cubic cells evoking primitive ductal cells. At stage 20, a row of ductal cubic cells went around the transverse portal sinus at the junction between M and liver cells. At stage 21, the DP developed at the periphery of periportal connective tissue and appeared in direct continuity with the hepatic duct (HDu). Four evaginations emerged from the DP and were growing up in the hepatic parenchyma. At stage 23, the DP appeared as a large network in continuity with the HDu located at the periphery of periportal M and presenting several evaginations radiating in the liver parenchyma. This work in the rat embryo permits the clear visualization of the development of the junctional zone in the hepatic hilum. Three phenomena are observed: (1) proximal left and right hepatic ducts and their segmental branches are derived from DP and not from the HDu; (2) the extrahepatic biliary system is in contact with the developing hilar ducts; (3) ductal maturation begins at the hilum and proceeds centrifugally. These observations are of great relevance in explaining pathological changes appearing at the hepatic hilum of neonates: hepatic polycystic disease, intrahepatic bile duct agenesis or atresia, and cyst of the extrahepatic bile duct.