The "Concept" of Parametria in the Treatment of Deep Infiltrating Endometriosis

Background Deep infiltrating endometriosis (DIE) is most commonly located at the uterosacral ligaments, rectovaginal septum, pararectal space and vesicouterine fold. A nodule within the uterosacral ligaments (i.e involvement of the dorsal parametrium), increases the complexity of surgical resection. Parametrial involvement in DIE cases occurs in 25% of patients with severe endometriosis, possibly with hypogastric/sacral plexus or sciatic nerve involvement. The bladder functional impairment, after surgery for DIE involved the parametria, may vary between the 6.5% to 32.8%. Preservation of the hypogastric and pelvic splanchnic nerves represents the key aspect in pelvic surgery to prevent postoperative voiding disfunction. Several techniques for the excision of DIE have been described, but large, prospective RCTs are lacking. In particular, a clear standardization of the parametrectomy for DIE is missing. Systematic reviews on the surgical treatment of DIE demonstrated that it is impossible to compare the literature about the parametrectomy for DIE, because to unclear definitions and lack of standardization. We therefore believe it is necessary to propose a standardization of the definition of parametrectomy performed during procedures for DIE, to allow a clear comparison in the future between scientific works on surgical treatment of DIE, as already widely accepted in gynaecologic oncology with the classification of radical hysterectomy of Querleu-Morrow. In particular we believe that the parametrectomy for DIE must be described based on its anatomical extension and focused on the concepts of nerve sparing dissection, and vascular structures preservation, to reduce the risk of complications due to ischemia (i.e. ureter fistula). Rationale A standardized description of the procedure (parametrectomy) will allow the comparison between the different techniques in terms of functionality preservation of the pelvic sympathetic and parasympathetic neural pathway. Therefore,