Endometriosis-associated pain syndrome: a nurse-led approach

Introduction

This October marks the International Association for the Study of Pain (IASP) Global Year against visceral pain. Amongst all the pain conditions, visceral pain is one of the most common reasons for consulting medical professionals, yet very little is understood of the mechanisms and aetiology underlying this type of persistent pain, which encompasses a variety of organs within the pelvic and abdominal areas.

The aim of this article is not to cover the established definitions of chronic pain or the new nomenclature of chronic pelvic pain, which is well covered in the new axial pain structural classification of the European Association of Urology (EAU). ¹ Rather it is aimed at looking at the pathway and treatments of a chronic persistent pelvic pain syndrome. The article aims to outline a multidisciplinary approach aimed at functional improvements. One particular condition will be examined and broad brush strokes of the general concepts we use in our urogenital and visceral pain department will be given. Our pathway for patients with endometriosis-associated pain syndrome (EAPS) will also be studied.

Epidemiology

A French study ² suggested that one-third of chronic pelvic pain in females is attributable to endometriosis but further American studies and other reviews suggest a much higher prevalence. ³ Although it is a diagnosis that many physicians are well aware of, there is a paucity of knowledge in the public domain of its aetiology, symptoms or treatment options and even more so with regard to the pain associated with endometriosis. ⁴ This leads to a delay in the diagnosis and treatment. ⁵

Patterns of referral in the UK reflect the fact that the majority of women who consult their general practitioner are not referred on to a specialist, despite numerous presentations with pelvic pain: 28% of women did not receive a diagnosis during 3 to 4 years of follow up after the first consultation and 60% of women had no evidence of a specialist referral. Women seen in secondary care for chronic pelvic pain are a highly selected group and are likely to represent only the tip of the iceberg. ⁶

Multiple studies^5,7,8 highlight the benefit of a multidisciplinary approach to the management of chronic pelvic and perineal pain however there is a scarcity of information regarding the structure of such a service.

Hurd ⁹ suggested in 1999 that chronic pelvic pain and endometriosis are two significant perplexing problems in gynaecology, and that endometriosis might not be the cause of their pain; however, his paper goes on to suggest three criteria for the diagnosis of endometriosis: first, that the pelvic pain should be cyclic because endometriosis is a hormonally responsive disease; second, endometriosis should be diagnosed surgically; and, third, medical or surgical treatment of endometriosis should result in prolonged pain relief.

We have come a long way in our understanding of endometriosis-related pain in the last decade and now know that these common fallacies are unhelpful and indeed not reflected accurately in this cohort of patients.

There is evidence from the 1990s that endometriosis staging in the current classification was not related consistently to pain symptoms. ¹⁰

A prospective German health insurance study following up patients over 4 years showed that only 7.5% of patients with the symptoms ascribed to endometriosis actually had surgical evidence of endometriosis subsequently, and thus symptoms are of limited predictive value. ¹¹

A large 5-year Australian ¹² exploratory study suggested that there might be an associated risk of endometriosis for those women who have worked as a flight attendant, service station attendant or health worker, particularly a nurse. However other findings ¹³ fail to support the presence of a unique psychological profile or even a disproportionate psychological disturbance in women with chronic pelvic pain due to endometriosis; in addition, no differences were obtained for ratings of depression, anxiety, mood factors or additional personality traits. These data suggest that, in general, when psychological disorders are observed in chronic pelvic pain patients, they most likely reflect the effects of chronic pain rather being causative of it.

Despite its prevalence, there is no optimal treatment for endometriosis; recurrence of the disease is a common problem. Laparoscopic surgery shows improved patient satisfaction outcomes in general health, quality of life and emotional wellbeing compared with medical therapies. ¹⁴

Most patients developed adhesions after radical surgical excision of endometriosis for pelvic pain. ¹⁵ The high incidence of adhesion formation after surgery for endometriosis emphasises the importance of optimising surgical techniques to potentially reduce adhesion formation. ¹⁵

Intra-abdominal adhesions are accepted as aetiological factors for infertility and other physical manifestations of secondary endometriosis; however, the contribution of adhesions to pelvic pain is less clear. The most common laparoscopic findings in patients both with and without pelvic pain were endometriosis and adhesions. Multiple adhesiolysis techniques have been employed, with the outcome of surgical procedures ranging from no pain relief to pain relief in 90% of patients. However, randomised trials have shown that adhesiolysis is ineffective in improving the outcome of the treatment of pelvic pain, possibly because of adhesion reformation. ¹⁶ The health-related quality of life in women is only partially restored by a combination of medical and surgical treatment. ¹⁷ Interestingly, adhesions are usually not described as an aetiological factor for pelvic pain in men; this might be related to a gender difference in pain perception or the possibility that adhesions per se do not cause pain.^4,18

Pathogenesis

Pain of any type is processed in nervous system activity. Rodent research ¹⁹ suggests that a major contributing factor for endometriosis pain is not the ectopic growths themselves, but sensory and autonomic nerve activity from nerves that have sprouted from nearby tissues to innervate the growths and affect activity of neurons in the spinal cord and brain.

Another hypothesis is that lesions may produce pain by compressing or infiltrating nerves near lesions, but it does not explain pain in situations in which nerves are not near lesions. Indeed, pelvic pain is not correlated with nerve fibres in adhesions or within endometriomas.

Importantly, endometriosis lesions must be vascularised to attach and survive. ²⁰ Blood vessels are innervated by sensory and sympathetic fibres; thus when blood vessels branch to vascularise developing lesions, termed angiogenesis, nerves innervating those blood vessels may also branch (neural sprouting), thereby enabling nerves to invade lesions.

Zhang et al ²¹ suggest that endometriosis is a neurovascular condition much like headache, a concept that was also suggested clinically. ²¹

Certainly here, as in other chronic pain type mechanisms, a combined complex circuitry of peripheral and central sensitisation mechanisms are in play.

Visceral pain is unique in that not all pain that is evoked is entirely linked to visceral injury, and the pain can be referred to other locations, is diffuse and poorly localised.

Prolonged noxious stimulation of the viscera, for example in a distended bladder, which is normally not a painful stimulus, can evoke increased excitability of viscerosomatic neurones in the spinal cord and subsequently cause pain. Once triggered, this central sensitisation is sustained despite the termination of noxious input, demonstrating that pain may be experienced even in the absence of peripheral noxious stimuli. ²² Specifically, these events are known to occur within the dorsal horn of the spinal cord and culminate in a process termed spinal sensitisation.^23,24

This establishes central hypersensitivity whereby normal sensory stimuli, in a magnified form, are perceived as pain. This may also result in muscle hyperalgesia, as muscles are closely related to viscera and the nerves. There is also an implication of chemical changes, for example in the central neuromodulator N-Methyl-D-aspartate. ⁷

There is also evidence that painful endometriosis can be classified as a mixed inflammatory and neuropathic pain condition ²⁵ or a neurovascular condition, ²⁰ both of which open new avenues for pain relief.

There is a lot of evidence in the literature to suggest that a combination of medical and surgical approaches to some aspects of pain associated with endometriosis works up to a limited ceiling. ²⁶ This is a reflection of the complex circuitry involved in the pathogenesis of pelvic pain, as discussed above. A common summary to most literature regarding treatment options for any persistent pain syndrome is that a multimodal treatment option is advocated.^26,27 In an extensive literature search the authors did not find an account of how this was currently facilitated in a centre from a patient perspective.

Patient pathway

In this section a new nurse-led pathway for patients with EAPS will be described. The assessment process will be used as a framework to explain interventions and referrals; in practice, explanations and referrals are discussed at the end of the consultation.

Patients are referred from the hospital’s endometriosis service usually when active treatment for endometriosis has been completed and, in the opinion of the gynaecological endometriosis team, there are no further surgical interventions yet the pain is persistent, or when pain appears unrelated to lesions. These referrals are triaged to be seen by clinical nurse specialists (CNSs) who specialise in urogenital pain management.

Patients with pelvic pain, dyspareunia and dysmenorrhoea often find it gratifying to be given a diagnosis of endometriosis, as they feel that a cause has been found for their pain, and that this cause has a viable and recognised treatment option, which is removal of endometriotic lesions, and the expectation is that excision will relieve pain. ²⁸

Counselling prior to laparoscopy is important to enable understanding of the fact that the primary function of surgery is confirmation of endometriosis, and to allow surgical treatment of the lesions, and that a laparoscopy is not the diagnostic modality for relief of pelvic pain.

There are many aetiologies of pelvic pain that present with symptoms resembling those of EAPS ²⁹ that are not diagnosable with laparoscopy, such as interstitial cystitis and irritable bowel syndrome. In fact, the pain-related diagnoses that are amenable to and possibly require a laparoscopy are quite limited. Howard ²⁹ would argue that diagnostic laparoscopy in modern gynaecology has a limited, if any, role and that, when laparoscopy is planned for women with chronic pelvic pain, it should be with a very high suspicion of a diagnosis and with plans to treat the disease operatively.

It is unfortunate that many women are left with the belief that, if a laparoscopy fails to provide a diagnosis of a pain generator or excision of the lesions does not remove the pain or it returns within a few months, then it means the pain is in her head or, to employ a term often used by clinicians, ‘supratentorial’.

The pain encompasses and impacts their relationships both social and intimate; they may be on the verge of unemployment or already unemployed. It is not uncommon for these patients to have been investigated by multiple specialists who, after extensive expensive procedures, have told them that their pain is psychosomatic as they do not have any active lesions, and they may also have been labelled as drug or attention seeking.

The CNS in the EAPS clinic provides a faster route to initial treatment and this is essential for this group of patients as, if they are managed correctly, they can stay in jobs or get back to work sooner. If managed poorly they could well bounce around the healthcare system and have yet more expensive unrequired investigations, which may lead further into a never-ending cycle of medicalisation, increase their pain and lead to the patient becoming further exasperated. ³⁰

Nurse-led service for EAPS

The CNS-led clinics run at the same time as the consultant clinics; patients are discussed after assessment but prior to presentation of treatment options. This pathway aims to reduce the long waiting lists that are common in our specialist urogenital pain clinics.

While there is evidence in the literature that supports the efficacy of nurse-led pain management programmes ³¹ there is a dearth of literature regarding CNS-led management of patients with EAPS.

Ryan ³² showed that in a nurse-led clinic for patients with fibromyalgia the mean number of hospital appointments fell significantly in the first, second and third years and 78% of patients reduced their general practitioner visits in the first year. They concluded that having nurse-led pain clinics can allow patients access to appropriate pain management strategies at an earlier stage in their conditions.

Managing pelvic pain patients with a timely multidisciplinary approach appears to be acknowledged as an ideal approach but it is expensive ³³ and resource heavy, and services are rare; however, when weighed against the cost for repeated referrals resulting in needless procedures it is money well spent. ³⁰

This is supported by an old study that found that patients attending a multidisciplinary pain clinic are nearly twice as likely to return to work, ³⁴ though it should be noted that this study looked at back pain and was methodologically poor. A more recent study of patients with neuropathic pain found improvement in quality of life outcomes and anxiety by application of a multidisciplinary clinic approach; however, there were acknowledged methodological errors in this study. ³⁵

In a specific neuropathic multidisciplinary pain clinic ³⁶ improvements in sleep, reductions in medication use and reductions in healthcare resource use were observed; however, pain severity only decreased after the 1-year follow up, whereas quality of life indexes and anxiety improved after 6 months.

Required training for CNS

The nurses are educated to masters level in pain, are experienced in general pain management and have four years’ of experience in the multidisciplinary urogenital pain management clinics; the development of the role of the nurse specialist in these clinics is dependant on their expertise. ³⁷

The consultation

The style of the consultation is a key element to the initiation of treatment, which is detailed below.

A thorough history is taken, after which the patient is provided with a diagnosis and comprehensive explanation. The mechanisms and reasons for their pain are explained and discussed along with an explanation for cessation of active treatment. Their ability to take on board the functional aspects of treatment hinge on an understanding of muscle hyperalgesia and the central sensitisation model.

Where necessary, the patient is referred to pain management physiotherapists and pain management psychologists for individual sessions covering pacing, tolerance, mood management and muscle training. This may also be delivered in a unique gender-specific pelvic pain management programme.

The consultation is 45 minutes and patients are given time to tell their story. They have often been told that their pain is in their mind as all the active disease has gone and they do not understand why they still have pain. A detailed history is taken from the patient, not from the clinic letters – it is important for these patients to feel heard. ³⁸ Patients are encouraged to describe what they think is the cause of their pain. It is accepted that this improves the clinician–patient relationship. ³⁹

The initial lengthy consultation starts the process of moving the patient from thinking about EAPS as being a lesion that can be removed to regarding it as a chronic disease process that is recognised and managed, ⁴⁰ and shifts the patient’s orientation to the problem of ongoing pain. Over time the aim is to help the patient to give up the relief of pain as their goal and entertain alternative means of realising their hoped-for goals. This may be by developing a new aspect of their hoped-for selves that matches their core values or by modifying their goals. ⁴¹

EAPS patients may present as very distressed as their hoped-for futures are blocked by persistent pain. Their distress may manifest as relentless searching for a cure, which has been observed as ‘doctor shopping’, which at best results in no abnormal findings and may result in further procedures. ⁴²

Example case

Conclusion

This patient’s experience reflects that of the majority of our patients who come to our specialist clinic as a last resort and feel hopeless. We find that our approach gives patients a framework of functional improvement whereby they have a readily accessible scientific explanation but also the support of a multidisciplinary approach to enable those very important functional improvements to be made in tandem.