The need for precise intrahepatic biliary anatomy is essential especially with the biliary intervention procedures as well as liver surgery including liver resection and transplantation to have a safe hepatectomy and reduce biliary complications [17,18,19,20].
While biliary anatomical variants are not a contraindication for liver donation, however, detailed accurate pre-operative identification is essential to avoid iatrogenic ligation of the donor or recipient’s major biliary tract, for example, ligation of aberrant RAHD or RPHD drainage into the left hepatic duct can cause cirrhosis [18, 19]. On the other hand, during right lobe transplantation, multiple biliary anastomoses in the recipient may be needed to prevent biliary obstruction .
MRCP is a noninvasive diagnostic technique with no radiation hazards and avoids the hazards of nephrotoxic contrast media and ERCP. It can show the high signal of the biliary and pancreatic secretions with dark background (sensitivity up to 90%) in normal biliary mapping [22, 23].
Breath-hold imaging can eliminate the artifacts caused by respiratory motion with the ability to improve spatial resolution by using a longer time of acquisition. It shows the advantage of a relatively short time of acquisition; however, the quality of images is affected by a low signal-to-noise ratio as well as low spatial resolution. The respiratory-triggered technique is able to extend the time of acquisition thus having higher spatial resolution .
There is a high prevalence of biliary variants which was shown in a many previous studies [25,26,27].
In the current study, we used Huang classification to categorize intrahepatic ducts according to the RPHD insertion.
The current study showed that vast subject number had intrahepatic duct Huang type A1 (typical type) representing 65.83% (n = 79) of the examined subjects followed by Huang A2, 11.67% (n = 14); Huang A3, 13.3 (n = 16); type A4, 7.5% (n = 9); and Huang type A5, 1.67 (n = 2).
This coincides with many previous studies [3, 15, 24, 28,29,30,31,32,33] while lower incidence of A1 (56%) was encountered in the study of Wang et al. .
Huang type A is optimum for right hepatic lobe living transplantation as it is simple; however, the right hepatic duct (RHD) length has a crucial impact as with sufficient length, one biliary-enteric anastomosis may be done easily, while in the case of short RHD, it may need modification as double anastomoses to avoid injury risk of the bile duct in hepatic resection [15, 19, 20, 35]. In the current study, Huang A1 was the dominant type representing 65.83% (n = 79) of the subjects included in our study. Due to the surgical importance of the distance between RPHD insertion and the right and left hepatic duct junction which assume a trifurcation pattern (common RAHD, RHPD, and LHD junction) for distance of 1 cm or less [20, 28, 35, 36], we had to subtype our subjects of Huang A1 based on the distance (L) between the insertion of RPHD and the right and left hepatic duct junction into S1 (L > 1 cm) and S2 (L = 1 cm or less). Accordingly, we had Huang A1 subtypes: subtype S1 (n = 52, 43.33%) and subtype S2 (n = 27, 22.5%).
In current study, the second predominant type was Huang type A3 in which the RPHD ends into the LHD, and it was seen in 13.3% (n = 16) which coincides with many previous studies [3, 15, 20, 29, 31, 36]. Also, it is close to the results of Basaran et al.  (Gawad 22) and Wang et al.  which was 20% and 18% respectively.
This variant may cause donor biliary injury and may necessitate double anastomoses to prevent postoperative biliary complication such as biliary leakage or segmental atrophy [9, 20, 36].
The third frequency was in the current study was for Huang A2 in which the RPHD open to the hepatic confluence (trifurcation) and represented 11.67% (n = 14) of our subjects which is near to the results of Wang et al.  which was 11% and higher than the frequency in the series of Basaran et al.  which was 5%. Some centers may avoid graft harvesting in biliary trifurcation to prevent a higher rate of postoperative complications.
In Huang types A4 and A5, there is aberrant right posterior hepatic duct that drains to the CHD or cystic ducts respectively this can be inadvertently ligated or injured during biliary surgery .
Double anastomoses may be needed in Huang type A4 also to prevent possible postoperative biliary complications in cases of liver transplantation [19, 20]. In current report, Huang A4 was seen in 7.5% of current subjects (n = 9) which is near to the results of Wang et al.  and higher than the results of Basaran et al.  who had donors having their RPHD drain into the main duct in 8% and 2.5% respectively.
We encountered Huang A5 in two subjects (1.67%) which is nearly of similar incidence reported in many previous studies [20, 37, 38].
Huang type 5 with RPHD draining into the cystic duct is of biliary surgical importance especially during laparoscopy as its damage may lead to biliary leakage and biloma [20, 37, 38].
In current study, 23 subjects had bile duct exploration or intraoperative cholangiograms, and 22 (95.65%) of them had the same MRC Huang type while only one case (4.35%) was reported as A2 at MRC but shown at intraoperative classification as Huang A3 due to RPHD insertion into the left hepatic duct’s distal end.
We had some limitation in our study; first, it was a small cohort study, and secondly, only 23 of our subjects were confirmed by intraoperative procedure.