The Association of Minimally Invasive Gynecologic Surgeons
…dedicated to safe, state-of-the-art surgery and health life-styles for women of all ages
Basic Research of Chronic Pelvic Pain
Ursula Wesselmann, M.D.
The International Pelvic Pain Society – Fall Meeting
Ft. Lauderdale, FL, October 20, 1999
Ursula Wesselmann M.D., John Hopkins University School of Medicine, Baltimore
Ursula Wesselmann MD
Assistant Professor
Johns Hopkins University School of Medicine
Depts. Of Neurology and Biomedical Engineering,
Blaustein Pain Treatment Center, Traylor Building 604,
720 Rutland Avenue, Baltimore, MD 21287
The International Association for the Study of Pain defines chronic pelvic pain without obvious
pathology as chronic or recurrent pelvic pain that apparently has a gynecological origin but for
which no definitive lesion or cause is found (Merskey and Bogduk 1994). This definition has not
been widely used in the literature (Campbell and Collett 1994). The problem with this definition
is that it (1) implies absence of pathology, which is not necessarily the case, and (2) it also
excludes cases in which pathology is present but not necessarily the cause of pain. In fact, the
relationship of pain to the presence of pathology is often unclear in women with chronic pelvic
pain. We will refer here to chronic pelvic pain as pelvic pain in the same location for at least 6
months (ACOG Technical Bulletin 1996). Many chronic pain states begin with a nociceptive
process, although that event might go unrecognized or unremembered.
Chronic pelvic pain is a common and debilitating problem that can significantly impair the
quality of life of women. Overall, a woman has about a 5 percent risk of having chronic pelvic
pain in her lifetime. Recent epidemiological data from the USA showed that 14.7 percent of
women in their reproductive ages reported chronic pelvic pain (Mathias et al. 1996). Fifteen
percent of these women with chronic pelvic pain reported time lost from work and 45 percent
reported reduced work productivity. Estimated medical costs for outpatient visits for chronic
pelvic pain in the United States are $881.5 million per year (Mathias et al. 1996). The personal
cost to the affected woman in terms of years of suffering, disability, marital discord, loss of
employment and unsuccessful medical intervention can be calculated less easily.
Patients with pelvic pain are usually evaluated and treated by gynecologists, gastroenterologists,
urologists and internists. In many cases the focus is on finding and treating the underlying
etiology of the chronic pain syndrome and these patients often undergo many diagnostic tests and
procedures. However, often the examination and work-up remain unrevealing and no specific
cause of the pain can be identified. Although these patients are often depressed, rarely are the
chronic pelvic pain syndromes the only manifestation of a psychiatric disease. In these cases it is
important to recognize that the patient is suffering from a chronic pain syndrome and to direct
treatment strategies towards symptomatic pain management. Despite the challenge inherent in
the management of chronic pelvic pain, many patients can be treated successfully (Wesselmann
1998). Effective treatment modalities are available to lessen the impact of pain and offer
reasonable expectations of an improved functional status.
Chronic pelvic pain belongs to the category of chronic visceral pain. Although persistent pain of
visceral origin is a much greater clinical problem that that from skin, the overwhelming focus of
experimental work on pain mechanisms relates to cutaneous sensation. The neurophysiological
mechanisms underlying visceral pain are poorly understood. In the past 10 years several different
animal models have been developed to study the behavioral manifestations, the neurophysiology
and neuropharmacology of somatic pain. The greatest contribution of these animal models may
lie in their use to study the effects of traditional analgesic therapies and to develop new analgesic
therapies, rationally targeted upon the pathophysiological mechanism. In contrast, very few
animal models have been developed to study visceral pain (Berkley and Hubscher 1995). The
reason for this is that, similar to the clinical situation, the manifestations of visceral pain in
animal models are more difficult to describe and to quantify than somatic pain. Until relatively
recently, it was often assumed that concepts derived from cutaneous studies could be transferred
to the visceral domain. However, there is experimental evidence demonstrating that the neural
mechanisms involved in pain and hyperalgesia of the skin are different from the mechanisms
involved in painful sensations from the viscera. We have recently developed an animal model of
inflammatory uterine pain in the rat (Wesselmann and Lai 1997, Wesselmann et al. 1998). This
model will allow to study pain pathways of uterus and the effects of interventions for the
treatment of uterine pain in the future.
Progress in chronic pelvic pain management is likely to come from the combination of basic
science and clinical research studies: (1) It is important to develop specific models of pelvic pain
in which the peripheral and central processing of visceral information and its pharmacological
manipulation can be studied. (2) Clinical studies are necessary to assess the characteristics of
pelvic pain syndromes and controlled clinical trials are important to study the effects of
traditional analgesics and of new analgesics targeted against the pathophysiological mechanisms
of visceral pain syndromes (based on basic science studies).
ACOG technical bulletin: Chronic pelvic pain, number 223 – May 1996. Int J. Gynecol and
Obstet 1996; 54:59-68.
Berkley KJ, Hubscher CH, Visceral and somatic sensory tracks through the neuraxis and their
relation to pain: Lessons from the rat female reproductive system., In: Gebhart GF (Ed). Visceral
Pain, IASP Press, Seattle, 1995, pp 195-216.
Campbell F, Collett BJ. Chronic pelvic pain. Brit J. Anaest 1994; 73:571-573.
Mathias SD, Kuppermann M, Liberman RF, Lipschutz RC, Steege JF. Chronic pelvic pain:
prevalence, health-related quality of life, and economic correlates. Obstet & Gynecol 1996;
Merskey H., Bogduk N. Classification of chronic pain. Seattle:IASP Press, 1994.
Wesselmann U, Lai J. Mechanisms of referred visceral pain: Uterine inflammation in the adult
virgin rat results in neurogenic plasma extravasation in the skin. Pain 1997, 73:309-317.
Wesselmann U, Management of Chronic Pelvic Pain. In: Aronoff GM (Ed). Evaluation and
Treatment of Chronic Pain., 3
Edition. Williams & Wilkins, Baltimore, 1998, pp 269-279.
Wesselmann U, Czakanski PP, Affaitati G, Giamberardino MA. Uterine inflammation as a
noxious visceral stimulus: behavioral characterization in the rat. Neurosci. Lett. 1998, 246:73-76.