Pain typology and incident endometriosis

Abstract

Study question: What are the pain characteristics among women, with no prior endometriosis diagnosis, undergoing laparoscopy or laparotomy regardless of clinical indication?

Summary answer: Women with surgically visualized endometriosis reported the highest chronic/cyclic pain and significantly greater dyspareunia, dysmenorrhea, and dyschezia compared with women with other gynecologic pathology (including uterine fibroids, pelvic adhesions, benign ovarian cysts, neoplasms and congenital Müllerian anomalies) or a normal pelvis.

What is known already: Prior research has shown that various treatments for pain associated with endometriosis can be effective, making identification of specific pain characteristics in relation to endometriosis necessary for informing disease diagnosis and management.

Study design, size, duration: The study population for these analyses includes the ENDO Study (2007-2009) operative cohort: 473 women, ages 18-44 years, who underwent a diagnostic and/or therapeutic laparoscopy or laparotomy at one of 14 surgical centers located in Salt Lake City, UT or San Francisco, CA. Women with a history of surgically confirmed endometriosis were excluded.

Participants/materials, setting and methods: Endometriosis was defined as surgically visualized disease; staging was based on revised American Society for Reproductive Medicine (rASRM) criteria. All women completed a computer-assisted personal interview at baseline specifying 17 types of pain (rating severity via 11-point visual analog scale) and identifying any of 35 perineal and 60 full-body front and 60 full-body back sites for which they experienced pain in the last 6 months.

Main results and the role of chance: There was a high prevalence (≥30%) of chronic and cyclic pelvic pain reported by the entire study cohort regardless of post-operative diagnosis. However, women with a post-operative endometriosis diagnosis, compared with women diagnosed with other gynecologic disorders or a normal pelvis, reported more cyclic pelvic pain (49.5% versus 31.0% and 33.1%, P < 0.001). Additionally, women with endometriosis compared with women with a normal pelvis experienced more chronic pain (44.2 versus 30.2%, P = 0.04). Deep pain with intercourse, cramping with periods, and pain with bowel elimination were much more likely reported in women with versus without endometriosis (all P < 0.002). A higher percentage of women diagnosed with endometriosis compared with women with a normal pelvis reported vaginal (22.6 versus 10.3%, P < 0.01), right labial (18.4 versus 8.1%, P < 0.05) and left labial pain (15.3 versus 3.7%, P < 0.01) along with pain in the right/left hypogastric and umbilical abdominopelvic regions (P < 0.05 for all). Among women with endometriosis, no clear and consistent patterns emerged regarding pain characteristics and endometriosis staging or anatomic location.

Limitations, reasons for caution: Interpretation of our findings requires caution given that we were limited in our assessment of pain characteristics by endometriosis staging and anatomic location due to the majority of women having minimal (stage I) disease (56%) and lesions in peritoneum-only location (51%). Significance tests for pain topology related to gynecologic pathology were not corrected for multiple comparisons.

Wider implications of the findings: Results of our research suggest that while women with endometriosis appear to have higher pelvic pain, particularly dyspareunia, dysmenorrhea, dyschezia and pain in the vaginal and abdominopelvic area than women with other gynecologic disorders or a normal pelvis, pelvic pain is commonly reported among women undergoing laparoscopy, even among women with no identified gynecologic pathology. Future research should explore causes of pelvic pain among women who seek out gynecologic care but with no apparent gynecologic pathology. Given our and other's research showing little correlation between pelvic pain and rASRM staging among women with endometriosis, further development and use of a classification system that can better predict outcomes for endometriosis patients with pelvic pain for both surgical and nonsurgical treatment is needed.

Study funding/competing interests: Supported by the Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development (contracts NO1-DK-6-3428, NO1-DK-6-3427, and 10001406-02). The authors have no potential competing interests.

Keywords: dysmenorrhea; dyspareunia; endometriosis; epidemiology; laparoscopy.

Figure 1

Percent distribution of anatomical site-specific pain in the perineal area by post-operative diagnosis. (A = endometriosis, B = other gynecologic pathology and C = normal pelvis). Significant differences (*P < 0.05 and **P < 0.01) between pair-wise pain report frequencies were conducted using the Tukey procedure for multiple comparisons (Elliott and Reisch, 2006; Zar, 2009). Women only indicated areas where they experienced regular pain, if any. To delineate significant differences between more than two groups (endometriosis, other gynecologic pathology and normal pelvis), values sharing a common superscript (a or b) are significantly different at *P < 0.05 and **P < 0.01. Study sample for these analyses includes all women undergoing a diagnostic and/or therapeutic laparoscopy or laparotomy regardless of clinical indication who participated in the ENDO Study (n = 473). There were no missing data in regards to pain location by post-operative diagnosis. Primary post-operative diagnosis among women with gynecologic pathology included uterine fibroids (n = 58), pelvic adhesions (n = 30), benign ovarian cysts (n = 46), neoplasm (n = 3) and congenital Müllerian anomalies (n = 10). Primary reason for surgery among women with a post-operative diagnosis of a normal pelvis included tubal ligation (n = 36), pelvic pain (n = 42), pelvic mass (n = 9), infertility (n = 16), and menstrual irregularities (n = 32), missing (n = 1).

Figure 2

Percent distribution of anatomical site-specific pain in the front of the body by post-operative diagnosis. (A = endometriosis, B = other gynecologic pathology and C = normal pelvis). For other information see Fig. 1.

Figure 3

Percent distribution of anatomical site-specific pain in the rear of the body by post-operative diagnosis. (A= endometriosis, B= other gynecologic pathology and C= normal pelvis). For other information see Fig. 1.