Posterior colpocentesis

Anatomical basis and core of the method

Posterior colpocentesis is a full-fledged diagnostic and therapeutic procedure, not merely a digital examination or reconstructive surgery.

• Access point: Posterior vaginal fornix (fornix vaginae posterior).
• Target area: Rectouterine pouch (excavatio rectouterina), also known as the Pouch of Douglas.

It is important to clearly differentiate this area from the vesicouterine pouch. The rectouterine pouch is precisely the lowest part of the peritoneal cavity in the pelvis. Due to this topographical feature, any pathological fluid in an acute intra-abdominal condition accumulates here under the influence of gravity. The needle insertion is performed taking into account the position of the uterosacral ligaments, between which the target "pocket" lies (the broad ligament of the uterus is not a landmark in this case).

Preparation and classical technique (Option 1)

Indications for the procedure: clarifying the diagnosis in suspected intra-abdominal pathology and evacuating accumulated exudate.

Preparation: The patient is placed in the gynecological position (supine, hips and knees flexed). The procedure requires adequate anesthesia — local anesthesia or short-term general anesthesia is used.

Course of the classical procedure:

1. The vagina is exposed with specula to visualize the cervix.
2. The posterior lip of the cervix is fixed. For this, strictly vulsellum forceps are used (using ring forceps or a uterine sound here is an error).
3. Vaginal specula are removed.
4. Traction (pulling) of the cervix with vulsellum forceps is performed anteriorly — toward the symphysis. It is a mistake to pull the cervix toward the sacrum, coccyx, or sacral promontory. Traction toward the symphysis is necessary to properly smooth out the posterior fornix.
5. Insertion: Performed with a long puncture needle attached to a dry syringe. The insertion point is in the midline, slightly posterior to the border between the smoothed fornix and the cervix.
6. The needle is advanced parallel to the pelvic axis to a depth of 2–3 cm.
7. Aspiration: The syringe plunger is slowly pulled back.

Evaluation of results and alternative technique (Option 2)

Evaluation criteria: If dark blood or a small clot appears in the syringe upon aspiration, this reliably confirms the presence of spilled blood in the peritoneal cavity.

Critically important rule: The absence of fluid in the syringe on the first attempt does not rule out intra-abdominal pathology. If the result is negative, do not immediately terminate the procedure. You must slightly shift the needle to the side (without completely removing it from the tissues) and repeat aspiration.

Technique with specula (Option 2): Unlike the classical method, here the vaginal specula remain in place throughout the entire procedure.

1. The vagina is exposed with specula.
2. A long retractor is introduced under the posterior lip of the cervix, pushing the tissues upward and anteriorly.
3. A spoon-shaped speculum is placed in the posterior fornix.
4. Insertion of the needle is performed strictly in the midline between the uterosacral ligaments. The direction of the needle in this option is strictly parallel to the cervix.

Class and exam questions

What else to study on this topic

• Topography of the rectouterine pouch (Pouch of Douglas) and its boundaries.
• Ligamentous apparatus of the uterus: uterosacral and broad ligaments, their role as anatomical landmarks.
• Types of pathological fluids in the pelvic cavity (blood, pus, serous exudate) and their diagnostic significance.
• Surgical instruments in gynecology: vulsellum forceps, vaginal specula, retractors, and ring forceps.
• Errors during puncture: incorrect direction of traction (toward the sacrum or coccyx) and incorrect insertion depth.

Other topics in the section «Pelvic and Perineal Surgery»

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.