Abstract
Backgrounds/Aims
Caudate bile ducts are routinely presented using negative images as X-ray-cholangiograms. Such information does not provide for instant surgical orientation of the relationships between caudate ducts and the liver itself−a paramount skill for successfully performing hilar cholangiocarcinoma resection and living donor/split transplantation. This study presents a 4-step procedure to prepare, dissect and present, high-quality, 2D/3D anatomical images of biliary caudate ducts in a surgically meaningful way.
Methods
Fresh cadavers had arteries and veins injected with colored-silicone and ducts bile-stained to facilitate recognition. Dissections were performed under magnification with microsurgical instruments. Stepwise 2D and 3D images were acquired.
Results
Dissection of silicone-injected specimens under magnification allows identification of caudate structures, its portions and processes while preserving tridimensional arrangement of caudate vessels, biliary ducts and collectors. Such dissections can help enhance cholangiogram interpretation and favor its direct correlation to intraoperative findings.
Conclusions
A procedure including: a) preparation of high-quality cadaveric livers, b) with silicone-injected vessels, c) dissected under surgical microscope and d) documented using 2&3D images aimed at enhancing the clinical understanding of the anatomy of caudate ducts is presented. It has potential to enhance morphological and clinical understanding of caudate ducts, being useful to anatomists and surgeons alike.
The biliary ducts of the caudate lobe must be dealt with during two major hepatobiliary surgical procedures: a) hilar cholangiocarcinoma resection1,2 and b) living donor/ split liver transplantation. 3,4 Surgical maneuvers and complication avoidance in both procedures involve detailed anatomical knowledge of this area. 5,6
Caudate bile duct anatomy has been extensively described using X-ray cholangiograms,7 CT cholangiogram,8-10 magnetic resonance cholangiopancreatography (MRCP)11 and liver corrosion casts.6,7,12 Because these are negative-image data, these methods fail to provide surgeons with information on the relationships between ducts and surrounding structures-as portal vein, arteries and the caudate lobe itself-and in demonstrating the microsurgical anatomy of the biliary ducts, including the second and third order branches to portions of caudate as paracaval, caudate process and Spiegel lobe.
This study presents a 4-step procedure to prepare, dissect and present, high-quality, 2D/3D anatomical images of biliary caudate ducts in a surgically meaningful way.
Anatomical specimens were obtained from the Anatomical Board of the State of Florida. Injection and dissections were undertaken at the George Schrader Colter International Anatomical Lab (Gainesville, US). This studied has been registered at the Institutional Review Board PAAP-HPS 2020 693716 04.
Fixation of fresh whole cadavers was accomplished after thorough saline cleanse of the vascular tree and arterial injection of formalin 10%. Specimens were kept refrigerated (−4°C) until whole-body arterial silicon injection and/or liver harvesting.
Using fresh cadavers treated so early, ducts were bile- stained and were easily recognizable during dissection.
Six livers were used in this study. After inspected in situ, each liver was resected by sectioning supra and infrahepatic vena cava and the distal liver pedicle.
Dissections were performed using 3× to 14× magnification of a surgical microscope (S21 Surgical Microscope; Carl Zeiss AG, Oberkochen, Germany) and standard microsurgical instruments.
The hilar fissure was fully dissected and exposed under magnification. All the connective tissue originated from Glisson’s capsule was cleaned from the hilar fissure (hilar plate total resection) to highlight the complete extra-hepatic relations of the caudate ducts and its bifurcations before entering the liver tissue.
The last dissection step was accomplished by total removal of vascular (portal and arterial) branches around Segment 1 to expose the caudate ducts and its relations to the lobe itself.
Stepwise 2D and 3D images were acquired using Nikon cameras (D80, D5100 and P100, Nikon Corp., Tokyo, Japan) and Nikon lenses (Nikon microlenses 2.0, 105 mm, Nikon Corp., Japan). 3D images were also acquired using Fuji cameras (Finepix Real 3D W1 and W3, Fuji Film Corp., Japan). All pictures were taken using a slidebar attached to a Manfrotto tripod (Manfrotto B55 tripod, Manfrotto, Italy). A ring flash was also used (Sigma Corp., Japan).15,16
The anatomical relationships exposed using this 4-step procedure are presented on Fig. 1 (silicone-injected specimens) and Fig. 2 (cleaned hilar fissure: ducts-only specimen) and summarized on Table 1.
The stepwise dissection under magnification allows identification of minute caudate structures and allows differentiation of caudate portions and processes. The tridimensional arrangement of caudate draining veins can be appreciated, and the biliary ducts and collectors followed. Such dissections can help enhance cholangiogram interpretation and favor its direct correlation to intraoperative findings.
To further exemplify the application of this 4-step procedure in highlighting the caudate ducts anatomy, images of a seldom-presented pattern of caudate biliary ducts have been chosen (Fig. 2). This specimen (Liver 1) has a common caudate duct, that collect all portions of Segment 1, entering the confluence of the right and left hepatic ducts. This pattern was observed by Healey and Schroy7 in 5% of livers,17 studied using cholangiography.
Anatomical understanding of the liver has changed in the last 2,000 years. Galen described 5-lobed livers in apes18 and even Vesalius19 perpetuated this misunderstanding in his Fabrica. Till renaissance, the internal liver anatomy had seldom been described.
In 1654, Francis Glisson described the inner anatomy of the liver (and its capsule/envelop) using “cooking” and “ants-digestion” methods, earlier described by Spiegel. Glisson named those methods “liver-defleshing”, as the final result would be a cast of intrahepatic vessels. 20
The enlightenment and the modern era brought the availability of organs to be studied (and injected), culminating with the studies of Cantlie, MacIndoe & Counseller, Hjortsjo, Goldsmith & Woodburne and Couinaud. 21,22 Couinaud and his collection of corrosion casts revolutionized the anatomical knowledge of the liver. 22
For the last 50 years, attention has been driven towards the caudate. Its anatomy has been studied using several methods. 7,9,11,12
Considering the caudate lobe complexity, divisions and micro-anatomical architecture, its published anatomical data has been mainly limited to “negative images”, including corrosion casts or X-ray cholangiograms. The missing relationships between caudate ducts and the liver itself are shortcomings of such methodologies. To further increase the difficulties in obtaining a realistic, surgically oriented representations of the caudate ducts, are articles presenting macroscopically dissected (de-fleshed), black-and-white figures of caudate lobes without differentiation between arteries, veins, portal branches and ducts. 15,23,24
Based on techniques described and routinely used in other areas of anatomical knowledge, this study comprises a 4-step procedure that includes: a) preparation of high- quality cadaveric livers, b) with silicone-injected arteries and veins an stained biliary ducts to facilitate recognition, c) dissected under surgical microscope and d) documented using 2 & 3D images aimed at enhancing the clinical understanding of the anatomy of caudate. Its application has the potential to enhance clinical and morphological of the caudate ducts, being of interest to anatomists and surgeons alike.
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FIGURES AND TABLE
Table 1
Specimen | Artery | Portal | Duct |
---|---|---|---|
Liver 1* | 2 branches: 1 left hepatic artery 1 Seg 6/7 artery | 3 branches: 1 right portal 2 left portal | |
Liver 2 | 3 branches: 2 left hepatic artery 1 Seg 6/7 artery | 4 branches: 1 right portal 2 left portal 1 main portal | |
Liver 3 | 2 branches: 2 left hepatic artery | 4 branches: 1 right portal 1 left portal 2 main portal | |
Liver 4 | 2 branches: 1 left hepatic artery 1 accessory right artery | 2 branches: 1 right portal 1 main portal | |
Liver 5 | 3 branches: 1 left hepatic artery 2 right hepatic artery | 3 branches: 1 right portal 1 left portal 1 main portal | |
Liver 6 | 2 branches: 1 right hepatic artery 1 accessory left artery | 3 branches: 1 right portal 1 main portal |