Endometriotic Peritoneal Implants
The mechanism through which endometriotic peritoneal implants may cause subfertility is probably by inducing a chronic pelvic inflammation. Peritoneal fluid becomes biochemically altered because it contains abnormally high concentrations of prostaglandins, proteases, inflammatory cytokines, and angiogenic cytokines, possibly interfering with the physiologic activity of the tubal ampulla. Moreover, some published data suggest that peritoneal fluid from women with endometriosis negatively affects multiple steps of the fertilization process by causing DNA damage to sperm, altering sperm motility, hindering sperm capacitation, hampering oocyte-sperm interactions, decreasing sperm binding to the zona pellucida, and impairing the acrosome reaction and sperm-oocyte fusion.
The diagnosis of endometriotic peritoneal implants requires direct visualization at surgery, preferably followed by biopsy and histologic confirmation. Without surgical evaluation, the presence of superficial serosal foci can only be hypothesized: In infertile women, the chance of having endometriosis is on average ~30%, which rises to roughly 50% if moderate to severe dysmenorrhea is also present. Cyclic or chronic pelvic pain as well as deep dyspareunia may coexist. Significant findings suggestive of endometriosis at vaginal examination include uterosacral ligament thickening and/or tenderness, Douglas pouch nodularity, and a fixed retroverted uterus.
Role of Surgery
The effect through which surgery would purportedly enhance the chances of natural conception in patients with peritoneal endometriosis is by reduction of pelvic inflammation, although this hypothesis has never been formally verified.
Two randomized controlled trials (RCTs) were conducted to evaluate the impact of the destruction of peritoneal endometriosis on pregnancy rate in infertile women. In the multicenter Canadian study, a significantly higher pregnancy rate was observed in women undergoing laparoscopy with ablation of peritoneal implants (63 of 172; 36.6%) as compared with those undergoing diagnostic laparoscopy only (37 of 169; 21.9%). Conversely, in the multicenter Italian trial, a comparable proportion of women achieved a pregnancy in the two study groups [(10 of 51; (19.6%) in the operative laparoscopy group and 10 of 45 (22.2%) in the diagnostic laparoscopy group]. After pooling the results of the two trials, the main outcome of interest (i.e., the rate of late pregnancies) was 26% in the operative laparoscopy group as compared with 18% in the diagnostic laparoscopy group (Fig. 1).
Results of randomized controlled trials comparing laparoscopic ablation of lesions with no surgery in infertile women with minimal or mild endometriosis. The diamonds represent the odds ratio (OR) of conception and the horizontal lines the 95% confidence intervals (CIs). Breslow-Day test for heterogeneity: χ2 3 = 13.24, p = 0.42. (From Vercellini P, Somigliana E, Viganò P, Abbiati A, Barbara G, Crosignani PG. Surgery for endometriosis-associated infertility: a pragmatic approach. Hum Reprod 2009;24:254–269. Reprinted by permission.)
When translating this result into clinical practice, the actual impact of the observed 8% increase in late pregnancies is greatly influenced by the background prevalence of endometriosis in the studied population. Accordingly, the number needed to treat (i.e., the number of operative laparoscopies required to obtain one additional pregnancy compared with treatment abstention) would be 12 with a background prevalence of endometriosis of 100%, 24 with a prevalence of 50%, and 40 with a prevalence of 30%. As for the surgical technique, a similar reproductive outcome has been observed with laparoscopic excision and electrocoagulation.[19,20]
Therefore, the clinical benefit of peritoneal implants ablation seems to be limited, especially if women are otherwise asymptomatic. In such a condition, a laparoscopy could not even be justified at least to relieve pelvic pain. As recently stated by the Practice Committee of the ASRM, "laparoscopic confirmation of asymptomatic endometriosis is almost always limited to uncovering minimal or mild disease. The therapeutic benefit of laparoscopy to increase fecundity in a woman with mild disease is minimal. The combination of these factors renders laparoscopy of asymptomatic women with infertility, simply to rule out or confirm disease, unwarranted."
Semin Reprod Med. 2013;31(2):133-143. © 2013 Thieme Medical Publishers