The PDIIA typically gives rise to three primary branches: the iliolumbar artery, the lateral sacral artery, and the superior gluteal artery. However, several meta-analyses exploring the anatomical characteristics of arteries originating from the anterior division of the internal iliac artery have revealed that these vessels can also emerge from the posterior division, albeit with variable frequencies [4, 5]. Notably, there is a noticeably low number of studies specifically examining the anatomical features of the PDIIA, including its branching pattern and pelvic location. Most previously published research on pelvic arterial anatomy has concentrated on the entire internal iliac system [6,7,8,9,10,11,12], frequently employing traditional classifications such as the Adachi system developed in 1928 [13]. The Adachi classification, with its five types and eight groups, posits that the umbilical artery is the primary stem of the internal iliac artery, with other pelvic arteries (e.g., superior gluteal, internal pudendal) being its branches from an embryological perspective [11]. However, this classification has undergone multiple revisions over the last century owing to oversimplification and practical limitations, failing to showcase all the internal iliac artery branches such as the uterine or iliolumbar arteries. Subsequent classifications have emerged to better elucidate iliac artery branching patterns and their clinical implications. The most recent classification, proposed by Balcerzak et al. [14], emphasizes practical aspects and visual representation of the main branches arising from the internal iliac artery, including the presence or absence of the umbilical artery. Yet, this new system focuses less on detailed branching patterns without descriptions of each individual branch.

Despite numerous existing classifications demonstrating the general anatomy of the internal iliac artery, there remains a scarcity of data specifically detailing the branching pattern and anatomical features of the PDIIA. Thus, our study introduces a novel classification of PDIIA branching patterns and their prevalence. Our classification identifies six types: type 1 (41.22%) features the iliolumbar artery as the first branch and the superior gluteal artery as the terminal branch. Conversely, type 2 (13.51%) begins with the lateral sacral artery, followed by the superior gluteal artery. Type 3 (5.41%) shows the obturator artery followed by the superior gluteal artery. Types 4 and 6 represent the PDIIA, giving rise to its three traditional branches in different orders. Type 4 (4.05%) showcases the lateral sacral artery as its first branch, and type 6 (3.38%) demonstrates the iliolumbar artery as its first branch. In both types, the superior gluteal artery is the terminating branch. Finally, type 5 consists of the superior gluteal artery as the first branch and the lateral sacral artery as the terminating branch (3.38%). Other observed variations (n = 42) were less prevalent (< 3.00%) and thus not included in our classification system.

Few studies have thoroughly examined the anatomy of the PDIIA. Bleich et al. [15] conducted a cadaveric study focusing on the general anatomy and clinical implications of the PDIIA, particularly in managing obstetrical hemorrhage. They found that in 62.30% of pelvic halves, posterior division arteries originated from a common trunk, whereas the remainder arose independently from the PDIIA. Additionally, the iliolumbar artery was the most frequently observed first branch (28.3%). Our imaging-based analysis reveals that the predominant initial branch of the PDIIA is the iliolumbar artery (57.76%), whereas the superior gluteal artery is commonly identified as the terminating branch (90.52%). We also examined the prevalence of each branch originating directly from the PDIIA, aligning closely with descriptions in major anatomical references. Notably, the superior gluteal artery (77.03%), iliolumbar artery (53.38%), and lateral sacral artery (32.43%) were the most frequent direct branches. Interestingly, the obturator artery was identified as a direct branch of the PDIIA in a notable percentage of cases (8.11%), contrasting with its conventional origin from the anterior division, a finding supported by other studies [6, 16]. Furthermore, branches that are traditionally known as branches of the anterior division were found to originate from the PDIIA in 13.51% of the individuals. Overall, our findings underscore the considerable variability in pelvic arterial anatomy.

A comprehensive understanding of the PDIIA and its branches is critical for various procedures directly involving these structures. The ligation of the internal iliac artery remains a viable option for managing pelvic hemorrhage [3], particularly in obstetrical and gynecological scenarios such as placenta previa, uterine rupture, and hemorrhage related to advanced pelvic cancers [17,18,19]. However, this procedure presents challenges, notably the importance of avoiding ligation proximal to the branches of the PDIIA to prevent complications such as buttock claudication and necrosis, as highlighted in previous studies [15, 20, 21]. Accurate identification of the anterior and posterior divisions of the internal iliac artery is crucial for successful ligation. Our study contributes valuable data on the arterial anatomy of the iliac system, including the median distance from the origin of the internal iliac artery to its bifurcation into the anterior and posterior divisions (42.48 mm). We also present an anatomical map highlighting the most frequent locations of this arterial bifurcation. The lower number of branches typically associated with the PDIIA (median = 3) compared with the more complex branching pattern of the anterior division aids in distinguishing between these vessels, facilitating precise arterial ligation.

Injury to specific branches of the PDIIA, such as the iliolumbar artery, can result in severe hemorrhage [22]. Therefore, accurate localization of PDIIA branches is crucial for effectively managing and controlling potential bleeding. Our study provides reliable data that can assist surgeons in this endeavor. By tracing from the origin of the PDIIA, our study outlines median distances to key branches such as the iliolumbar (9.63 mm), lateral sacral (11.88 mm), and superior gluteal arteries (10.02 mm), aiding in precise branch identification and subsequent hemorrhage control if required. It is important to note that the morphometric properties of the analyzed vessel may showcase age-related differences. This is shown in Table 5, where all measured parameters increased with older age. This includes the origin of the branches of the PDIIA, data that are relevant for interventional radiologists who control bleeding with endovascular treatments, such as embolization [23].

The variable vasculature of the pelvis presents significant risks for surgeons performing gynecological procedures, particularly vaginal sacrospinous fixation for apical support [24]. The sacrospinous ligament is in close proximity to critical structures such as the internal pudendal and inferior gluteal vessels, the sciatic nerve, and branches of the sacral nerve plexus as they exit the pelvis via the greater sciatic foramen [25, 26]. Notably, the anatomy of the inferior gluteal artery is highly variable, and its proximity to the sacrospinous ligament places it at heightened risk during vaginal sacrospinous fixation [27]. In our cohort, the inferior gluteal artery originated from the PDIIA in 5.41% of cases. This aberrant origin can lead to a more tortuous and unpredictable course of the artery, increasing the likelihood of injury during surgical procedures. Such injury could result in severe hemorrhagic complications [28]. Additionally, our study highlights that branches typically arising from the anterior division often originate from the PDIIA, further underscoring the complexity and variability of pelvic vasculature.

The present study undoubtedly has several limitations. Radiological imaging is limited to evaluating arteries that are hemodynamically functional. As a result, this introduces a significant bias when assessing anatomical variations of the PDIIA and other vascular structures. Furthermore, the studied sample consisted solely of results from the Polish (white) population. Despite its limitations, this study was aimed at providing comprehensive morphological and anatomical data on the PDIIA, aligning with the principles of evidence-based anatomy [29, 30].