The difficulty of accessing the Pouch of Douglas (POD) surgically was one of the factors that popularized the move to laparoscopic and robotic approaches for hysterectomy. The conditions that create POD entry problematic are conditions that cause obliteration of the POD space such as endometriosis, prior surgery, pelvic inflammatory disease, or diverticulitis to name a few. To determine whether preoperative ultrasound is a feasible tool for visualization of the pouch of Douglas (POD) to facilitate a safe vaginal entry for direct vaginal trocar insertion for visualization of uterosacral ligaments and pelvic cavity.

Endovaginal ultrasound-guided needle insertion of a trocar into the POD was performed in six fresh frozen female cadavers and in a live sheep animal model. Six female cadavers with the pelves intact were available for the study.  The cadavers and the ewe were placed in the dorsal lithotomy position.  Pelvic ultrasound was performed using a BK FlexFocus triplane probe.  The cul-de-sac space was identified as a fluid-filled space clear of bowel or adhesions, with visible bowel displacement with probe pressure to detect the “sliding sign” (Fig 1).  A veress needle was advanced under vaginal ultrasound guidance to confirm POD localization.  Access to the Pouch of Douglas was achieved using a blunt, extra-long metal trocar  (Fig 2).

Laparoscopy and cadaveric dissections confirmed safe cul-de-sac entry and accurate trocar placement.  The average age of fresh frozen cadavers was 60, and a BMI of 27.  All cadavers had intact uteri. Two of the fresh frozen cadavers underwent laparoscopic inspection and four direct inspections via a laparotomy to confirm safe POD entry for both ultrasound-guided needle placement and trocar placement in all cases.  The uterosacral ligaments were identified with direct visualization and laparoscopic dissection in all cases at the level of the ischial spine.  All the other adnexal structures could be seen.

The strength of this study is the use of cadavers and a live ewe model to confirm the feasibility of ultrasound-guided entry into the POD prior to clinical large scale application of this procedure.  We believe ultrasound-guided entry into the POD in the appropriately trained hands can overcome the challenges associated with culdotomy in anticipated difficult cases.  Ultrasound-guided direct vaginal trocar entry into the POD is a good option to avoid prevent accidental bowel and vascular injuries.  We advocate further studies to prove the safety of this modality.  In the case of the unavailability of the ultrasound in the operating room or lack of expertise, there are two clinical options in performing the ultrasound.  It can be performed preoperatively by a skilled sonologist or a gynecologic surgeon in the office to confirm the patency of the POD.

Ultrasound-guided POD entry for pelvic cavity was found feasible in the development of a safe vaginal entry in a ewe and a cadaveric model, thereby possibly negating the need for laparoscopic / robotic umbilical observation in the future.

Leonardi, M., et al., Diagnostic accuracy and reproducibility of predicting cul-de-sac obliteration by general gynaecologists and minimally invasive gynaecologic surgeons. Journal of Obstetrics and Gynaecology Canada, 2019. 41(4): p. 443-449. e2.
Alshiek, J., L. Bar-El, and S.A. Shobeiri, Vaginal Robotic Supracervical Hysterectomy in an Ovine Animal Model: The Proof of Concept. Open Journal of Obstetrics and Gynecology, 2019. 09(08): p. 1114-1129.
Baekelandt, J., Total vaginal NOTES hysterectomy: a new approach to hysterectomy. Journal of minimally invasive gynecology, 2015. 22(6): p. 1088-1094.