Evaluation of the Concordance of Portal Vein and Biliary Duct Variations: A Retrospective Donor Series

Introduction

Accurate definition of hepatic vascular and biliary anatomy is crucial for safe liver transplantation and hepatobiliary surgery [1]. Undetected portal or biliary variants can result in unexpected intraoperative complications such as bleeding, ischemia, or biliary injury, and can compromise both donor and recipient outcomes [2–4]. In living donor liver transplantation, donor safety is paramount because a healthy individual undergoes hepatectomy; therefore, all relevant variants must be identified before surgery. Because the portal vein and biliary systems develop in parallel during embryogenesis, an anatomical concordance between them has been suggested [5–7]. A clinically relevant question is whether preoperative vascular imaging-particularly triphasic CT angiography can provide enough information to anticipate biliary anatomy and guide surgical planning. However, the literature on this relationship is limited and sometimes contradictory [8–10].

The aim of this study was to retrospectively evaluate and statistically analyze the relationship between PV and BD types in a large cohort of living liver donors. By focusing exclusively on this population and combining preoperative CT angiography with intraoperative cholangiography, we sought to contribute more robust data to the literature.

Material and Methods

IMAGING AND CLASSIFICATION:

Portal vein anatomy was assessed using triphasic multiplanar CT angiography after intravenous administration of Iohexol. PV variants were classified according to Cheng et al [4] as:

All CT images were reviewed by a senior radiologist experienced in hepatobiliary imaging. In all donor hepatectomies, intraoperative cholangiography was routinely performed after hilar dissection and before parenchymal transection to obtain real-time biliary mapping. Bile duct anatomy was categorized using the Couinaud classification [11,12], from BD Type 1 to BD Type 6, which is the most widely used system for surgical planning [13].

DEFINITIONS:

“Classical concordance” was defined as PV Type 1 coexisting with BD Type 1. “Anatomical concordance” was defined as a direct one-to-one match between PV and BD types (PV1-BD1, PV2-BD2, PV3-BD3). Demographic data (age, sex), graft type (right or left lobe), PV type, and BD type were recorded in a Microsoft Excel database.

STATISTICAL ANALYSIS:

The relationship between PV and BD types was analyzed using the chi-square test or Fisher’s exact test where appropriate. A P value <0.05 was considered statistically significant. The study was approved by the Institutional Ethics Committee (64–2025/12.03.2025) and conducted in accordance with the Declaration of Helsinki.

Results

DISTRIBUTION OF ANATOMICAL VARIANTS:

Portal vein types were distributed as follows: PV Type 1 in 362 donors (85.6%), PV Type 2 in 51 (12.1%), and PV Type 3 in 10 (2.4%). The most frequent bile duct pattern was BD Type 1 (n=272; 64.3%), followed by BD Type 2 (n=50; 11.8%), BD Type 3A (n=42; 9.9%), BD Type 3B (n=53; 12.5%), BD Type 4 (n=3; 0.7%), and BD Type 6 (n=3; 0.7%). Representative IOC images are shown in Figure 1, and the proportional distribution of BD subtypes according to PV type is summarized in Table 1.

OVERALL RELATIONSHIP BETWEEN PV AND BD TYPES:

The coexistence of PV Type 1 with BD Type 1 (“classical concordance”) was observed in 239 donors (56.5%), representing the most frequent combination. Among donors with PV Type 1 (n=362), BD Type 1 was seen in 239 (66%), whereas 123 (34%) had a variant BD configuration. In donors with non-Type 1 PV anatomy (Types 2 and 3, n=61), BD Type 1 was found in 33 (54.1%), while 28 (45.9%) had variant BD anatomy (Table 2). Although variant BD patterns were more common in PV Types 2 and 3, the difference between PV Type 1 and non-Type 1 PV donors regarding the coexistence of variant BD was not statistically significant (P=0.098).

SUBGROUP ANALYSIS BY PV TYPE:

In donors with PV Type 2 (n=51), BD Type 1 remained the most common (52.9%), but BD Type 3A and 3B together accounted for 23.5%. Similarly, in PV Type 3 donors (n=10), BD Type 1 was observed in 60%, and BD Type 3 variants in 30%. Although numbers were limited, these findings suggest a tendency for more complex biliary anatomy in association with PV Types 2 and 3. Due to sample size, statistical testing for these subgroups was not applicable (df=0, P=1.0).

ANALYSIS BY GRAFT LOBE:

When analyzed according to graft side, classical concordance (PV Type 1 + BD Type 1) was identified in 222 of 385 right-lobe donors (57.7%) and in 13 of 38 left lobe donors (34.2%), a statistically significant difference (χ2=7.58, P=0.0058). The overall anatomical concordance (direct PV–BD type match) was 64.9% in right-lobe and 52.6% in left-lobe donors (χ2=2.27, P=0.131). These results indicate that while concordance is generally higher in right-lobe grafts, left-lobe donors display greater variability in biliary anatomy (Table 3).

SEX-BASED ANALYSIS:

The distribution of PV and BD types did not differ significantly between male and female donors (PV: p=0.953; BD: P=0.418), suggesting that anatomical variation is not sex-related.

Discussion

This study investigated the anatomical concordance between portal vein (PV) and bile duct (BD) variations in living liver donors and demonstrated a statistically significant association between their configurations. Our results provide new evidence that 21% of donors with a “normal” PV Type 1 had BD Type 3 variants. This finding emphasizes that even donors with standard vascular anatomy may present complex biliary structures that could complicate donor surgery and graft implantation.

Clinically, identifying BD Type 3 variants is particularly important, as these configurations may predispose to bile leakage or stricture formation if not recognized during donor hepatectomy or recipient anastomosis. The observation that such variants occur even in PV Type 1 donors suggests that relying solely on vascular anatomy to predict biliary configuration can be misleading. Our data also indicate that the left lobe can display greater biliary variability than traditionally assumed. Importantly, no donor in this series experienced biliary complications or mortality, confirming the safety of combining CT angiography and intraoperative cholangiography (IOC) for comprehensive preoperative and intraoperative evaluation.

The statistically significant association between PV and BD anatomy (P=0.0028) supports the concept of parallel embryological development of the hepatic vascular and biliary systems [5,6,14]. During liver morphogenesis, both structures arise from the same embryonic plate and undergo segmental remodeling. This shared developmental origin explains the frequent coexistence of certain PV and BD variants. Our results are consistent with previous reports. Takeishi et al (2015), in a series of 407 living donors, demonstrated a strong correlation between PV and BD variations (P<0.0001) [14]. Similarly, Guler et al (2013) found that 54% of donors with variant PV anatomy also had biliary anomalies [15]. The concordant findings across studies reinforce the reliability of our data and confirm that vascular and biliary systems exhibit parallel variability patterns.

In our donor cohort, BD Type 1 was the most prevalent configuration (64.3%), which closely matches previously reported frequencies 63% by Choi et al [16] and 65.8% by El Hariri et al [17]. This similarity indicates that our population reflects general anatomical trends. The prevalence of BD Type 2 and BD Type 3 variants was 11.8% and 22.5%, respectively. The relatively high frequency of BD Type 3 variants, compared with earlier studies [16,18,19], highlights the need for increased awareness of right posterior sectoral ducts draining into the left hepatic duct, as these patterns may pose challenges during graft preparation and biliary reconstruction.

Bile duct variations occurred more frequently in donors with PV Types 2 and 3. As shown in Table 1, donors with PV Type 2 had BD Type 1 in 52.9% and BD Type 3 (3A + 3B) in 23.5%. Among PV Type 3 donors, BD Type 1 was seen in 60%, and BD Type 3 variants in 30%. This trend indicates that variant PV anatomy often coincides with increased biliary complexity. Such coexistence may reflect subtle embryological heterogeneity in the branching of the hepatic diverticulum and vitelline veins. Therefore, when a PV variant is detected preoperatively, detailed biliary assessment becomes essential to avoid postoperative complications.

The presence of BD Type 3 variants in 21% of PV Type 1 donors is another key finding, demonstrating that a seemingly “normal” portal configuration does not exclude the possibility of significant biliary anomalies. This finding is particularly relevant for left-hepatectomy and left-lobe donation, where a right posterior sectoral duct draining into the left hepatic duct can increase the risk of bile leakage or residual segmental obstruction in the donor.

“Classical concordance” (PV Type 1 with BD Type 1) was observed in 57.7% of right-lobe donors but only 34.2% of left-lobe donors, with a statistically significant difference (P=0.0058). Although right-lobe grafts are generally considered more technically challenging, our findings indicate that the left lobe may have greater biliary variability. This difference reflects not an inherent complexity of the left lobe, but rather the high prevalence of BD Type 3 variants in that group (3A + 3B=57.9% of left-lobe donors). Notably, even among left-lobe donors selected preoperatively for “normal” PV anatomy, IOC revealed classical PV–BD harmony in only 34.2% of cases.

Previous studies often describe left-lobe grafts as safer and simpler due to the predictable course of the left hepatic duct and portal vein [20,21]. However, our findings challenge this perception, showing that the left lobe can also present complex biliary arrangements. Thus, comprehensive biliary evaluation should always precede graft side selection. The decision between right- and left-lobe donation must prioritize anatomical clarity rather than assumptions of simplicity.

No significant difference was observed between male and female donors in the distribution of PV or BD variations (PV: P=0.953; BD: P=0.418), suggesting that these variations arise from individual developmental differences rather than sex-related factors. The systematic use of intraoperative cholangiography in our series significantly strengthened the anatomical accuracy of our findings. IOC provides real-time, high-resolution visualization of biliary branching and is particularly valuable when MRCP results are equivocal. Several authors have emphasized its importance for surgical safety, especially in patients with non-Type 1 biliary anatomy [17–19,22].

Finally, the international composition of our donor population comprising individuals from multiple ethnic and geographic regions-enhances the generalizability of these results. By integrating preoperative triphasic CT angiography with routine intraoperative cholangiography, this study demonstrates that detailed mapping of both vascular and biliary structures is indispensable for minimizing risk and optimizing outcomes in living donor liver transplantation.

Conclusions

In this large series of living liver donors, we demonstrated a significant association between portal vein anatomy and bile duct variations, supporting the concept of parallel embryological development of the hepatic vascular and biliary systems. However, the detection of clinically relevant biliary variants in donors with normal portal vein anatomy – particularly the presence of BD Type 3 in 21% of PV Type 1 cases – indicates that portal vein type alone is not a reliable predictor of biliary complexity. Moreover, the lower rate of classical concordance in left-lobe donors challenges the traditional assumption that the left lobe is anatomically simpler and highlights the need for meticulous biliary mapping in these cases. For these reasons, preoperative triphasic CT angiography should routinely be complemented by intraoperative cholangiography to ensure safe donor hepatectomy, accurate graft selection, and prevention of biliary complications. A comprehensive anatomical evaluation remains essential in living donor liver transplantation.