Comprehensive anatomy of the superior hypogastric plexus and its relationship with pelvic surgery landmarks: defining the safe zone around the promontory.

Abstract

Pelvic surgery carries an inherent risk of autonomic nerve injury leading to genitourinary and bowel dysfunction due to the close proximity of the superior hypogastric plexus (SHP). The aim of this study was to define the detailed anatomy of SHP and identify its relationship with the vascular landmarks and ureters for pelvic autonomic nerve-preserving surgery. A cadaveric study on the detailed anatomy of the SHP was conducted in our surgical anatomy research unit. Between 02/2019 and 10/2019, macroscopic anatomical dissections were performed on 45 fresh adult cadavers (39 male, 6 female). Distances between the SHP, major vascular structures, and other anatomical landmarks were measured. Three types of SHP morphology were observed: mesh (64.8%), single nerve (24.4%), and fiber (10.8%). SHP bifurcation was located inferior to the aortic bifurcation in all cases; however, it was observed cranial to the promontory in 80% of the cases, whereas 18% were caudally and 2% were over the promontory. The closest vessels to the left and right of the SHP bifurcation were the left common iliac vein (LCIV) (86.2%, the mean distance was 8.49 ± 7.97mm) and the right internal iliac artery (RIIA) (48.2%, mean distance was 13.4 ± 9.79mm), respectively. At SHP bifurcation level, the lateral edge of the SHP was detected on the LCIV in 22 cases and on the RIIA in 10 cases for the left and right side of the plexus, respectively. The distance between the SHP bifurcation and the ureter was 27.9mm on the right and 24.2mm on the left. The width of the left (LHN) and right hypogastric nerves (RHN) were 4.35mm and 4.62mm at 2cm below the SHP bifurcation, respectively. LHN was on the vascular structures in 13 cases, whereas RHN in only 1 case, 2cm below the SHP bifurcation. Understanding the location of the SHP, including its relationship with important anatomical landmarks, might prevent iatrogenic injury and reduce postoperative morbidity in the pelvic surgery setting.