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

(1) BASIC RESEARCH OF CHRONIC PELVIC PAIN

(2) CLINICAL TREATMENT OF CHRONIC PELVIC PAIN

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).

REFERENCES

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;

87:321-327.

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.