Diagnosis, treatment and follow up of women undergoing conscious pain mapping for chronic pelvic pain: a prospective cohort study

Authors

  • A Swanton,

    1. Department of Obstetrics and Gynaecology, Wexham Park Hospital, Slough, Berkshire, UK
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  • L Iyer,

    1. Department of Obstetrics and Gynaecology, Wexham Park Hospital, Slough, Berkshire, UK
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  • PW Reginald

    Corresponding author
    1. Department of Obstetrics and Gynaecology, Wexham Park Hospital, Slough, Berkshire, UK
      Dr PW Reginald, Department of Obstetrics and Gynaecology, Wexham Park Hospital, Wexham Street, Slough, Berkshire SL2 4HL, UK. Email philip.reginald@hwph-tr.nhs.uk
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Dr PW Reginald, Department of Obstetrics and Gynaecology, Wexham Park Hospital, Wexham Street, Slough, Berkshire SL2 4HL, UK. Email philip.reginald@hwph-tr.nhs.uk

Abstract

Objective  To assess the efficacy of conscious pain mapping in diagnosing and treating chronic pelvic pain (CPP).

Design  Prospective cohort study.

Setting  Gynaecology Department, UK District General Hospital.

Population  Forty-three women diagnosed with CPP.

Methods  The cohort was followed up for 18–24 months after diagnosis and treatment based on conscious pain mapping.

Main outcome measures  Improvement of pain assessed by using visual analogue scale (VAS) pain scores at 6-month follow up.

Results  Thirty-nine women had successful conscious pain mapping. Pelvic pathology was identified in 18, pelvic congestion in 13 and 8 women had normal pelvic organs. In 35 women (90%), conscious pain mapping identified the cause of pain. Five out of eight women (63%) who were judged to have a normal pelvis had positive findings at pain mapping. VAS scores fell significantly from pre-treatment to post-treatment values at 6-month follow up (P < 0.01). Overall, 26 women (74%) felt that their symptoms had improved after treatment based on findings at pain mapping. However, we concluded that pain mapping only contributed to the diagnosis and treatment in seven women (27%), who may not have received appropriate diagnosis and treatment if they had a laparoscopy under general anaesthetic.

Conclusions  Conscious pain mapping is a useful additional investigation in the management of women with CPP. It can be employed in women with a negative laparoscopy or with visible pathology where the conventional treatment has failed.

Introduction

Chronic pelvic pain (CPP) is a significant problem for both GPs and gynaecologists. CPP is commonly defined as pain originating in the lower abdomen or pelvis for duration of at least 6 months, which is not exclusively cyclical or intercourse related and not relieved by narcotic analgesics.1 Women who describe symptoms which are solely related to either menstruation (i.e. dysmenorrhoea) or to sexual intercourse (i.e. dyspareunia) are usually excluded. The annual prevalence of CPP in primary care was estimated as 38/1000 in women between 15–73 years of age,2 compared with figures reported for asthma (37/1000) and back pain (41/1000).

Investigations are often uninformative at eliciting a cause and unsuccessful surgical intervention is not uncommon. A diagnostic laparoscopy can be extremely useful in identifying pathology and up to 40% of laparoscopies performed by gynaecologists are for CPP.3 No visible pathology is identified in 35% of women, endometriosis detected in 33% and adhesions in 24% of women, respectively.3,4 Other data have shown up to 31% incidence of pelvic congestion in women with CPP.5 The number of negative laparoscopies remains high and women are often discharged back to primary care on the basis of this result. However, it is not uncommon for women to return with recurrence of symptoms and have further inappropriate surgical intervention.

The identification of pathology at laparoscopy may not necessarily be the cause of the pain. The poor correlation between symptoms and extent of endometriosis diagnosed at laparoscopy is well known,6 and other pathology such as adhesions may not be the cause of CPP either.7 Symptoms that are incorrectly attributed to pathology identified at laparoscopy can not only label women but also put them at risk of further unnecessary surgery.

Conscious pain mapping involves a laparoscopy under local anaesthetic, which is an interactive approach with the woman in order to elicit the cause of their pain. The technique could potentially reduce the number of unnecessary interventions, thereby eliminating inherent risks to the woman, and subsequently produce a more cost–effective course of treatment. Laparoscopy under local anaesthesia has been performed for many years.8 First described in 1996, conscious pain mapping has been practised for a relatively shorter period9 and the number of studies is limited. Conscious pain mapping aims to localise areas within the pelvis responsible for CPP in order to provide specific treatment options.10

A literature search has been performed and there are no follow-up studies to determine the efficacy of diagnosis at conscious pain mapping by assessing the response to appropriate treatment. The aim of this study was to assess any symptomatic improvement after treatment, based on the diagnosis by conscious pain mapping, thereby determining whether the procedure is a useful diagnostic tool in the management of CPP.

Methods

Ethical approval was obtained from the East Berkshire Ethics Committee prior to starting the study. Forty-three women with CPP were recruited for conscious pain mapping. The mean age of the women was 33 years (range 24–44 years). Thirty-one women were parous, having had one or more children, while the remaining 12 were nulliparous. The duration of pain ranged from 6 months to 3 years. Prior to conscious pain mapping, women were asked to score their average intensity of pain using a visual analogue scale (VAS) of 0–10. The aims of the study and procedure were explained in detail and the women provided informed consent. We provided the choice of conversion to general anaesthesia if local anaesthesia was unsuccessful, either during the same procedure or at a later date.

Contraindications to the technique were the following: body mass index (BMI) > 30 kg/m2, surgical phobia and proven psychiatric disorders, including generalised anxiety disorder. Women with a BMI > 30 kg/m2 were excluded in order to minimise potential technical difficulties.

The anaesthesia involved a combination of an intravenous anxiolytic and opioid medication, together with local anaesthetic infiltration at the trocar sites. Premedication was not administered. Alternating doses of midazolam 70 μg/kg and pethidine 500 μg/kg were administered intravenously and repeated at 5- to 10-minute intervals if required. Not more than two doses were required for any of the women in the study. After infiltrating the skin, the deeper layers of tissue in the subumbilical area were thoroughly anaesthetised using 20 ml of 0.25% bupivicaine with adrenaline 1:200 000 in a fan-shaped manner with a spinal needle. A small incision was made transversely below the umbilicus and the woman was asked to distend her abdomen and the Verres needle introduced simultaneously. Pneumoperitoneum was achieved by 1.5 l of nitrous oxide. A 10-mm trocar was inserted as the woman was again asked to distend the abdomen. All laparoscopies were performed by the same surgeon (P.W.R.), using an Olympus 10-mm laparoscope with a 0° lens (A5290A). Illumination was provided by a 250-W, high-intensity cold light source and the images were viewed on a high-resolution colour monitor using a chip camera. The suprapubic area was infiltrated with 20 ml of 1% lignocaine for insertion of the second trocar. Adequate infiltration of the peritoneum was made under direct vision and a second (5-mm) trocar then introduced.

The operator was blind to the exact side on which the woman experienced pain. A probe was introduced through the second port and the pelvic organs and large bowel were systematically mobilised. Any adhesions identified were stretched in order to try and reproduce the symptoms. Identified pathology, such as endometriosis or pelvic varicosities, was again probed systematically. Women were instructed to score the pain on probing using a verbal rating score (VRS) of 0–10 and also were asked whether any of the operator’s manipulations reproduced the pain that she complained. Pathological findings were probed after the whole pelvis was systematically screened twice, to try and achieve maximum consistency. The identified pathology was judged to be the cause of pain if the probing reproduced the pain that the woman complained of.

Medical or surgical treatment was started depending on the diagnosis made at conscious pain mapping. Women were followed up at 6 months, 12 months and at 18 months or whenever clinically indicated. Women who underwent subsequent surgical procedures were followed up until 24 months. During the follow up at 6 months, the pain intensity was scored again using a VAS. A comparison of VAS scores recorded pre-treatment and at 6 months was analysed using Wilcoxon signed rank test. Complete resolution of the pain or a 70% reduction of the VAS was considered to be an improvement. Further improvement of pain, after subsequent medical or surgical interventions, was recorded at follow-up visits but not included in the evaluation.

Results

Forty-three women were recruited for conscious pain mapping of whom 39 had a successful conscious pain mapping procedure. Four of the 43 women were excluded from the initial results. In three women, inadequate anteversion of the uterus rendered the procedure unsatisfactory and the remaining woman did not tolerate insufflation of the peritoneal cavity. Twenty-three women had undergone previous diagnostic or therapeutic surgical intervention for pelvic pain.

In 35 women (90%), probing of the pelvic organs reproduced the pain. In four women (10%), no site of pain was identified. Three of these women had normal pelvic organs. The remaining woman had an ovarian cyst, which was not symptomatic when probed or manipulated. No complications were recorded, either at the time of the procedure or at follow up.

Pelvic pathology was identified in 18 women, pelvic congestion in 13 and the eight remaining women were judged to have normal pelvic organs providing three major categories (Figure 1). The median pain score (VRS) on probing the pelvic organs when judged to be responsible for the pain was 8 (range 7–10), compared with 2 (range 1–4) when the organ probed was not thought to be the cause of pain.

Figure 1.

Flow diagram representing cohort of women with CPP and clinical outcome after 6-month follow up.

The pathology group can be further subdivided as follows: adhesions (n= 5); endometriosis (n= 6); trapped ovary (n= 3); fibroids (n= 2) and ovarian cyst (n= 2). Appropriate management, either medical or surgical, was implemented following the diagnosis of symptomatic pelvic pathology.

In 12 out of the 18 (67%) women, the pelvic pathology identified was judged to be the cause of pain. Of these women, nine (75%) felt their symptoms had improved following treatment and this was sustained at follow up. The three women who did not improve following treatment had three separate diagnoses made, including adhesions, a uterine fibroid and endometriosis.

The pain was not reproduced by probing the area of pathology observed in 6 of the 18 women (33%). Of these women, two had adhesions, two had endometriosis, one had an ovarian cyst and the remaining woman had a trapped ovary. In five women, an alternative site of pain was identified. In the woman with the ovarian cyst, no alternative site of pain was found, and the woman continued to complain of pain despite aspiration of the cyst at the time of pain mapping. The woman with a trapped ovary was lost to follow up. In the remaining four women, two had tender ovaries and uterine tenderness was noted in the other two women. Following subsequent treatment, all these four women (80%) showed improvement.

Thirteen women were diagnosed with pelvic congestion syndrome based on the findings of a congested uterus with varicosities in the broad and infundibulopelvic ligaments. One woman was lost to follow up and one woman declined the treatment offered. They were both excluded from subsequent analysis. In each of the remaining 11 women, medical ovarian suppression was administered. One woman did not respond to ovarian suppression and no further treatment was given. All the remaining ten women (91%) improved at 6 months, but on stopping treatment, symptoms returned in five women (45%). Surgical management was then recommended, as directed by the initial pain mapping. Pain mapping records of these women identified the uterus only to be tender and reproducing pain in one woman and she had a total abdominal hysterectomy (TAH). In another woman, the uterus and both ovaries were tender and we performed a TAH and bilateral salpingo-oophorectomy (BSO). In the remaining three women, the uterus and only one ovary was tender and the treatment was TAH with unilateral ovarian conservation. All five women were subsequently pain free at follow up.

In the eight women who were judged to have normal organs, conscious pain mapping identified the site of pain in five women (63%). In two women, the site of pain was interesting. They had both had a TAH with conservation of the ovaries in the past. Although there was no obvious pathology visible at laparoscopy, probing of the vaginal vault reproduced the pain. On closer examination, both women had areas of peritoneal puckering over the vaginal vault measuring approximately 1 cm in diameter. These areas were infiltrated with local anaesthetic, and subsequent probing did not reproduce the pain. These areas were ablated at a subsequent laparoscopy under general anaesthetic with a carbon dioxide laser. In the remaining three women, the uterus was found to be exquisitely tender in one woman, both ovaries in the second and the left ovary in the third. All these women underwent ovarian suppression. At 6 months, only one woman who had bilaterally tender ovaries was pain free. Subsequently, the woman with the tender uterus underwent a TAH, and we performed a left salpingo-oophorectomy for the woman with a tender left ovary. Both women were pain free after 24-month follow up.

No identifiable site of pain was found in three (38%) of the eight women in this group. One woman was referred to the gastroenterology team, which diagnosed irritable bowel syndrome and the woman’s symptoms improved after treatment. The second woman was referred to the orthopaedic team, which diagnosed a musculoskeletal disorder and again the woman improved following a discectomy. The remaining woman was lost to follow up.

In summary, the pain was reproduced and the site identified in 35 of the 39 women (90%) who had a successful laparoscopy. Overall, significant reduction in pain scores was noted in 26 women (74%). The median pain score before treatment in women where a site of pain was identified was 8.5 (range 7.0–10.0). The median pain score at 6-month follow up after treatment was 1.0 (range 0.0–5.0), which is statistically significant (P < 0.01).

Discussion

Laparoscopy is a widely used investigation in the management of CPP as it still remains the only tool capable of diagnosing peritoneal endometriosis and adhesions that are sometimes responsible for pelvic pain. However, in as many as 50% of women with CPP, laparoscopic examination under general anaesthesia does not find a cause, and in some women, the pathology identified is not necessarily the cause of pain. It is therefore reasonable to expect that an interactive approach would enable identification of the actual cause of pain and thereby appropriate treatment could be initiated.

The validity of the diagnosis is supported by the significant reduction of pain noted at 6-month follow up after the initial treatment. Of the 35 women in whom a cause was identified at conscious pain mapping, 26 reported an improvement of symptoms at 6 months after the appropriate treatment based on the diagnosis made at laparoscopy. However, the role of conscious pain mapping was deemed useful in seven women as the outcome in the remaining 19 women would have been the same even if the laparoscopy was performed under general anaesthesia. Although the possible placebo effect of surgery can be significant, the authors feel that 6-month follow up is enough time to negate any effects as a result of this.

Not unexpectedly, this study noted that the observed pathology was not the cause of pain in 6 of the 18 women diagnosed in this group. However, an interactive approach adopted in this study enabled the identification of an alternative cause of pain and improvement after treatment in four of them. Yet, the outcome would not have been any different in 14 of the 18 women had the laparoscopy been performed under general anaesthesia.

Pelvic congestion was thought to be the cause of pain in 13 women, with improvement noticed after ovarian suppression in 10. The results would likely have been the same even if the laparoscopy was performed under general anaesthesia. It is not uncommon for women to have recurrence of pain after the cessation of ovarian suppression, and in some women with intractable pain interfering with their quality of life, abdominal hysterectomy and BSO is successful.11 In our study, surgical options became necessary in five women who had significant recurrence of pain and would have been therefore considered for BSO with hysterectomy. Although this option may relive pain, it is not optimal in women with pelvic congestion as they are often young with a mean age of 33 years.12 The identification of the specific organ tenderness at conscious pain mapping may become useful in conserving the ovaries in some women. In four of the five women in this study, pain mapping identified nontender ovaries, which were therefore conserved, with women continuing to remain pain free at 24-month follow up. Clearly, this would not have been possible if laparoscopy was performed under general anaesthesia, but the value of this approach needs further evaluation in future studies.

Conscious pain mapping identified the cause of pain in five of the eight women with a normal pelvis. In three out of the five women there was an improvement with appropriate treatment at 6 months. The remaining two women needed subsequent surgical intervention which was only possible as the site of pain was clearly identified through the interactive procedure. Had the laparoscopy been performed under general anaesthesia, no cause of pain would have been identified in any of them.

It could be argued that the sensation evoked by probing of the pelvic organs may be not be comparable with the women’s symptoms. However, this was possibly overcome by establishing the cause of pain only when probing reproduced the pain experienced by the woman. It could be criticised that the stimulus on probing was variable, but this possibility was reduced by a single operator and that the pelvic organs were systematically probed twice in order to achieve consistency. It is evident from this study that conscious pain mapping actually contributed to the diagnosis and treatment in only 7 of the 26 women (27%) who improved at 6 months after treatment based on the diagnosis. However, identifying the site of pain at conscious pain mapping subsequently helped to offer appropriate surgical options in five women in the pelvic congestion group and two women in the normal pelvis group, all of whom improved. Perhaps similar results could have been achieved by identifying and recording the site of pain during a careful bimanual examination, at least in some cases. This area needs further evaluation.

Conclusion

This study has confirmed that the observed pathology is not always the cause of pain and in such cases an alternate site of pain was identified and treated successfully as a result of this interactive approach. Furthermore, pain mapping can be employed as a useful additional tool in women who have failed to respond to conventional treatments. In cases of pelvic congestion, conscious pain mapping may provide the possibility of conserving ovaries in some women who may require surgical intervention.

An interactive approach enables an individualised and sometimes limited surgical intervention. It can also be useful in identifying unusual causes of CPP. However, in order to further assess the efficacy of conscious pain mapping, large randomised controlled trials with comparison of long-term follow up will be necessary.

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