Pelvic Floor, Abdominal and Uterine Tenderness in Relation to Pressure Pain Sensitivity Among Women with Endometriosis and Chronic Pelvic Pain

Objective: Pelvic floor pain, abdominal wall pain, and central nervous system pain amplification can be contributing factors in chronic pelvic pain (CPP), however; limited research has investigated the association of pelvic floor, abdominal, and uterine tenderness with central nervous system pain amplification. We assessed whether pressure pain thresholds on the non-dominant thumbnail, a marker of central nervous system pain amplification, were associated with pelvic floor, abdominal, and uterine tenderness among women with endometriosis or CPP.

Study Design: We conducted a cross-sectional study among 88 females with endometriosis and/or CPP. Abdominal (6 locations), pelvic floor (6 locations) and uterine (1 location) tenderness were assessed via a standardized physical exam. Participants reported their pain levels (0-10 scale) with application of 2 kg of pressure at each area, with a pain rating of ≥4 on the 0-10 scale considered moderate to severe pain. Pain sensitivity was measured on the non-dominant thumbnail by applying discrete pressure stimuli using a previously validated protocol.

Results: Overall, 50% (44/88), 42% (37/88), and 58% (51/88) of participants reported high pelvic floor, abdominal, and uterine tenderness, respectively. Pressure intensities needed to elicit 'faint' and 'mild' pain were lower for participants with high vs. low pelvic floor tenderness (median intensity for 'faint' pain = 0.50 kgf/cm(min-max:0.25-3.25) vs. 1.06(0.25-3.00), p-value = 0.006; median intensity for 'mild' pain = 2.00(0.63-4.88) vs. 2.63(0.75-6.00), p-value = 0.03). No association was observed between pressure pain sensitivity and abdominal or uterine tenderness (p > 0.11). Participants with endometriosis without pain were less likely to have high pelvic floor (22.2%), abdominal (11.1%), and uterine (25.9%) tenderness compared to participants with endometriosis with pain (63.0%, 50%, 65.2%, respectively) and participants with chronic pelvic pain (60%, 73.3%, 93.3%, respectively).

Conclusions: These results suggest that high pelvic floor tenderness among women with endometriosis/CPP may be a marker of heightened pain sensitivity suggestive of central nervous system pain amplification and may impact treatment response. Future research should examine whether this clinical phenotype predicts response to medical and behavioral treatments (e.g, anti-convulsants, behavioral therapy, Physical Therapy).