The Yabuki space: landmark in pelvic anatomy and surgery

Gynecological surgery, especially oncological surgery, is a daily challenge with an impressive development over time. The anatomy of the pelvis and its study have led to the development of new surgical techniques with the discovery of spaces and structures that bring considerable benefits to the postoperative result, both oncological and hemodynamic or func-tional. Radical nerve-sparing hysterectomy is a topical issue that significantly improves patients' quality of life.


INTRODUCTION
The history of gynecological surgery has evolved based on anatomical findings. In 1895, Mackenrodt's transverse cervical ligament was a controversial dis covery, with some considering it an extension of the parameter, and the cardinal ligament terminology was agreed upon [1,2]. In 1945, Wertheim and Meigs revolutionized cancer surgery [3].
The spaces are delimited, from the point of view of the clinical anatomy, by at least two fasciae and contain connective tissue [4,5]. Their exposure by separating the fascia leads to the creation of surgical cleavage spaces, but, from a surgical point of view, not all avascular spaces are delimited by two fasciae [4,[6][7].
Laparoscopy in gynecology has led to the revelation of new spaces and dissection plans, and nervesparing procedures have been improved. The pararectal and paravesical spaces can be divided into medial or lateral spaces, and the total number of spaces varies between six and eight [4][5][6][7][8][9]. The spaces are avascular and contain fatty tissue and connective tissue being derived from different embryological structures. Knowing these spaces and accessing them prevents unnecessary blood loss, injury to the viscera and ureter [4,[8][9][10].
The spaces of the pelvis are divided into lateral spaces and medial spaces, being named according to the nearest organ [4]. The lateral spaces are paravesical, pararectal and Yabuki's fourth space. The paravesical and pararectal spaces are in turn divided, by the umbilical artery, respectively the ureter, into lateral and medial spaces [4,11]. The medial spaces are represented by the Retzius space (retropubic), the rectovaginal, presacral or retrorectal, vesicovaginal or vesicocervical spaces [4,11].

THE YABUKI SPACE: DESCRIPTION
Yoshihiko Yabuki described the Yabuki space, also called the fourth space, in 2000. The delimitations of the Yabuki space are given by the bladder and ureter ligament, which contains the splanchnic nerves that intervene in the bladder, its dissection being possible by dissecting the cranial portion of the bladder-uterine ligament, having utility in nerve-sparing surgery [4].
Along with the Okabayashi, Latzko and medial paravesical spaces, the Yabuki space is one of the most important landmarks in the nerve-sparing tech niques of gynecological oncological surgery [4,[12][13].
The Yabuki space is located in the area of the ureter insertion into the bladder, and unlike the other pelvic spaces, it is not lined by the peritoneum, so this space is between the anterior face of the uterus and the entrance of the ureter into the bladder [14,15].
The cervicovesical fascia consists of an anterior and a posterior leaf and delimits the Yabuki space. The anterior sheet accompanies the ureter at the entrance to the bladder, and the covering of the ureter in the anterior sheet leads to the formation of bladder pillars. The posterior leaf of the cervicovesical fascia communicates at the levator level with the endopelvic fascia [7,15].

IMPORTANCE OF YABUKI SPACE
A retrospective study analysed 440 patients with IBI to IIB cervical cancer. Patients were divided into two groups according to the chosen surgical method. The two methods approached were the traditional one and the one that uses anatomical landmarks. The blood loss and the ureteral injury were significantly lower in the anatomical space group [14].

CONCLUSION
Knowing the anatomical spaces of the pelvis are important both for operating comfort and for improving the quality of life of patients. The Yabuki space is a space of remarkable importance by preserving the bladder innervation and by the open approach of a space that provides important interoperative information for the orientation and pre servation of tissues.