Do women with PPP have different pain thresholds than healthy women?

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A cross-sectional observational study has found that women with persistent pelvic pain (PPP), with or without confirmed endometriosis, have significant lower pain thresholds compared to healthy women.

The Swedish study in the journal Acta Obstetricia et Gynecologica Scandinavica assessed pain thresholds for heat, cold and pressure with quantitative sensory testing at six anatomical locations: low back (L5), right and left low anterior abdominal wall, right and left abdominal wall at level of umbilicus and anterior tibial tuberositas of dominant leg.

A control group of 55 healthy women without pelvic pain symptoms was compared with 37 women with PPP who had been admitted for diagnostic laparoscopy on the suspicion of endometriosis. 

The three modalities of pain were measured within 4 weeks of planned surgery in the PPP group. Compared with the control group, the PPP group showed significantly lower pain thresholds on all locations. 

Principal investigator Preben Kjølhede, MD, PhD, a professor of children and women’s health in the Department of Clinical and Experimental Medicine at Linköping University in Sweden, was inspired to undertake the study because of his daily clinical duties with women suffering from PPP/endometriosis and the helplessness of many of his fellow clinicians in helping these women, due to their lack of knowledge and understanding of the mechanisms of pain.

“Pain thresholds were evaluated by means of quantitative sensory testing of heat and cold using a Medoc TSA II NeuroSensory Analyzer and of pressure measured by a handheld algometer,” Dr. Kjølhede told Contemporary OB/GYN. 

In the PPP group, pain thresholds for heat correlated significantly with the Short Form Health Survey 36 dimension of bodily pain, whereas thresholds for cold correlated with Short Form Health Survey 36 bodily pain and with symptoms of depression.

“These findings are indicative of sensitization,” Dr. Kjølhede said. The duration of pelvic pain correlated significantly positively with reduced pain thresholds; for example, the longer the duration, the more sensitization. 

“For the first time, we have found a time-dependent correlation between duration of pelvic pain and pain thresholds, which indicates that pain duration is a crucial factor in the development of sensitization,” Dr.  Kjølhede said.

However, the study observed no difference in pain thresholds between women with (n = 13) and women without (n = 24) biopsy-proven endometriosis. 

The investigators were surprised by the results in three ways. “First, we found widespread alterations in pain thresholds, indicative of central sensitization in women with PPP,” Dr. Kjølhede explained. “Secondly, pain and not endometriosis per se seemed to be the driving force in the development of sensitization; and thirdly, as with the first surprise, we demonstrated a significant correlation between duration of pelvic pain and the pain thresholds.”

Dr. Kjølhede is hopeful that study results will motivate clinicians to pay more attention to young women seeking first-time treatment for PPP and to treat the pain and the etiology of the pain adequately in order to avoid or reduce the risk of developing a state of sensitization.

“This field of research should be encouraged and deserves high public priority and funding,” he said. “Much suffering can be eliminated in the future by an active and effective treatment of symptoms of endometriosis in young women.”

If traditional treatment for suspected endometriosis does not rapidly alleviate symptoms, the diagnosis should be reconsidered, and invasive diagnostic tools should be employed to verify the diagnosis, according to Dr. Kjølhede. “At that point, treatment should be delegated to multidisciplinary teams specialized in PPP,” he said.  

Disclosures:

Dr. Kjølhede reports no relevant financial disclosure.