Endometriosis affects about 2.5%-3.3% of reproductive-aged women and is characterized by extrauterine growth of endometrial tissue consisting of endometrial glands and stroma. Its depth ranges from superficial to deep infiltration.
When described as deep infiltrating endometriosis (DIE), the disease involves lesions that are invasive and that extend into areas or organs that are in direct contact with already affected areas. Although the theory of migration of endometrial glands may help to explain endometriosis in general and superficial disease in particular, the prevailing opinion currently is that DIE may result from metaplasia of remnants of Müllerian tissue.
DIE lesions penetrate greater than 5 mm under the peritoneal surface and can cause severe pelvic pain. The lesions are mainly composed of smooth muscle with active glandular epithelium, which causes fibrosis and eventually their nodular characteristics.
In cases in which the DIE lesions affect areas such as the rectovaginal space (as well as the uterosacral ligaments and the rectocervical area), treatment is more successful with a surgical approach.
Although rectovaginal lesions are eventually diagnosed through surgical methods, clinical examinations and imaging should be performed to support the surgical approach.
On medical history, many of these patients present with pelvic pain, dysmenorrhea, dyspareunia, or infertility.
Clinical examination must be done to help appreciate the location of the nodular lesion. The size of the nodule may be palpated on bimanual exam and can involve uterosacral ligaments, the posterior vaginal wall, the anterior rectal wall, and the posterior fornix.
Preoperative imaging, especially transvaginal and transrectal ultrasound and MRI, will establish the distribution and depth of the deep lesions.
The presence of deeply infiltrative endometriosis and the resulting alteration of normal anatomical planes make this one of the most challenging surgical cases that gynecologists encounter. Laparoscopic treatment requires an intimate understanding and application of pelvic anatomy, and the surgical fundamentals of visualization and traction-counter-traction, as well as electrosurgery.
Pathophysiology
The presence of deep endometriotic lesions in the posterior cul-de-sac is, again, likely a consequence of metaplasia of Müllerian rests, and the nodules are composed of smooth muscle proliferation and fibrosis, which is a result of infiltration.
The endometriotic foci migrate to the rectovaginal area, where hyperplasia of smooth muscle incites an inflammatory response; this evolves into retraction, which then leads to pelvic fibrosis and a subsequent reduction in uterine mobility and distortion of the pelvic anatomy.
DIE lesions have been classified through studies by Dr. Philippe Koninckx and his colleagues into three types based on their depth of invasion and location.
Type I lesions are conically shaped rectovaginal septum nodules and are located between the posterior and anterior walls of the vaginal mucosa and rectal muscularis, respectively. Lesions categorized as type II are deeply located and form from the posterior fornix to the rectovaginal region. They are typically covered by extensive adhesions causing retraction. The most severe lesions—type III—are composed of spherical nodules. The largest dimension of these lesions is located under the peritoneal fold of the rectouterine pouch of Douglas. The cranial movement of these posterior fornix lesions eventually causes the nodules to join the anterior rectal wall and creates an “hourglass”-like appearance.
Anatomy
It is important to appreciate the relationships of the avascular spaces and their relevance to the dissection of the obliterated cul-de-sac and excision of rectovaginal endometriosis. Also remember that the ureter enters the pelvis over the bifurcation of the common iliac and medial to the infundibulopelvic ligament (see photo below).
The pararectal space is bordered laterally by the pelvic sidewall, anterolaterally by the cardinal ligament, and medially by the rectal pillars. The ureter courses beneath the peritoneum and through the rectal pillar.
The rectovaginal space is bordered laterally by the uterosacral ligaments, anteriorly by the vaginal fascia, and posteriorly by the rectal fascia.
The potential surgical space between the ureter and uterosacral ligament is utilized to transect the uterosacral ligament, which provides a means of access from the pararectal space into the rectovaginal space.
Instrumentation and Process
Surgical management of DIE is essential for restoring pelvic anatomy, relieving debilitating pelvic pain, and eliminating endometriotic nodular foci. Laparoscopic surgery provides magnified views of the posterior cul-de-sac and its pathology, and results in less postoperative pain and decreased recurrence of adhesions.
Instruments typically utilized during these procedures include monopolar scissors, bipolar coagulation, and the Harmonic scalpel.
Energy sources that provide the least amount of lateral spread are key in these procedures as the relationships of the pelvic organs, ureters, and rectum are exceptionally close.
The systematic approach of resecting these nodules entails restoring the normal anatomic relationships of the adnexa and sigmoid, then dissecting the obliterated cul-de-sac and performing a thorough excision of the rectovaginal endometriotic lesions.