Bile duct anatomy of the Anatolian Caucasian population: Huang classification revisited

Background and objectives Living donor liver transplantations (LDLT) donor candidates are being assessed with MRCP (magnetic resonance cholangiopancreatography) to identify their suitability for standard surgical techniques. Variations of the bile duct anatomy play an important role in donor selection and in the selection of the resection technique. If bile duct anatomy is misrecognized, complications may occur. Anatomic variations are classified according to the origin of the right posterior hepatic duct (RPHD). According to the so called Huang classification, type A1 is the most, and type A5 is the least frequent variation. These frequencies were initially validated on Chinese population. Later studies revealed significant variability in frequency for the so called trifurcation, the variation in which a common junction of RHPD, right anterior hepatic duct (RAHD) and left hepatic duct (LHD) (A2) exists. In this study we aimed to determine the bile duct anatomy variations for the Anatolian Caucasians. Methods One hundred and thirty-four healthy subjects were investigated under 1.5 T MRI, with breath-hold (expiration) heavily T2-weighted turbo spin echo (TSE) static fluid imaging (TR/TE = 8,000/800). The sequence has permitted three to five oblique coronal thick sections (40 mm) around a common axis. Sequences were repeated until anatomically interpretable images were obtained. Diagnostic images could not be obtained in 22 subjects. Radiologists who were fully experienced in LDLT assessment investigated these images, and classified them for the surgical variations of the bile duct anatomy. One hundred and twelve subjects (58 men, 54 women) who were classified were between 14 and 81 years of age (mean: 39.3; SD 14.1). According to Huang classification, 61 of them (55%) were classified as type A1 (normal right and left hepatic duct junction), 16 (14%) as type A2 (common junction of RAHD, RHPD and LHD), 24 (21%) as type A3 (aberrant drainage of RPHD to left main duct), and 11 (10%) as type A4 (aberrant drainage of RPHD to main hepatic duct). When subjects, in whom the distance (d) between RPHD insertion and the right and left hepatic duct junction is less than 1 cm, are classified as type A2, the type A1 prevalence decreases to 28%. For the entire population that distance was between 3 and 25 mm (mean: 9.8, SD: 4.8). Accordingly, the frequency of type A1 anatomy was 8-29% lower than the respective frequency in Chinese population. Conclusion From the surgical perspective, close proximity (d < 1 cm) of RPHD to right and left hepatic duct junction is considered as type A2 variation. According to that concept, type A1, usually accepted as the dominant anatomic variation, is encountered only in 28% of the Anatolian Caucasians. We have proposed a modified surgical classification in which Huang type 2 was subdivided into types K2a (close proximity) and K2b (trifurcating). The predominance of K2 types in the population of the study may necessitate the use of bench ductoplasty in many liver grafts.