Chronic pelvic pain is common, affecting perhaps one in six of the adult female population. Much remains unclear about its aetiology, but chronic pelvic pain should be seen as a symptom with a number of contributory factors rather than as a diagnosis in itself. As with all chronic pain it is important to consider psychological and social factors as well as physical causes of pain. Many non-gynaecological conditions such as nerve entrapment or IBS may be relevant. Women often present because they seek an explanation for their pain.
There is frequently more than one component to chronic pelvic pain. Assessment should aim to identify contributory factors rather than assign causality to a single pathology. At the initial assessment, it may not be possible to identify confidently the cause of the pain.
Given the incomplete understanding of the genesis of pelvic pain, it may be necessary to keep an open mind about the cause and consider unusual diagnoses, such as hernias or retroperitoneal tumours, or consider causes which until recently might have been dismissed as rarities, such as musculoskeletal pain.
Pelvic pain which varies markedly over the menstrual cycle is likely to be attributable to a hormonally driven condition such as endometriosis. The cardinal symptoms of dysmenorrhoea, dyspareunia and chronic pelvic pain are said to be characteristic of endometriosis or adenomyosis. In a prospective study of 90 women undergoing laparoscopy or laparotomy, the combination of clinical examination and trans vaginal ultrasound accurately identified ovarian endometriosis but not peritoneal disease. Symptoms alone were a poor predictor of finding endometriosis at surgery, but a causal association between the disease and severe dysmenorrhoea probably exists.
The existence of pelvic venous congestion as a cause of chronic pelvic pain remains controversial. A recent systematic review of diagnosis and management of this condition found no valid diagnostic tests, although ovarian suppression was effective in treating pelvic pain symptoms. In women suspected of having this condition,both progestins and gonadotrophin-releasing hormone (GnRH) agonists were shown in randomised controlled trials to effectively decrease pain during therapy, with GnRH agonists showing higher efficacy.
Adhesions may be a cause of pain, particularly on organ distension or stretching. Dense vascular adhesions may cause chronic pelvic pain. However, adhesions may be asymptomatic. Evidence to demonstrate that adhesions cause pain or that laparoscopic division of adhesions relieves pain is lacking. However, in a randomised controlled trial, 48 women with chronic pelvic pain underwent laparotomy with or without division of adhesions. Although overall there was no difference between the two groups, a subset analysis showed that division of dense, vascular adhesions produced significant pain relief. In a 2003 study of 100 women, no difference in pain scores was found between a group undergoing laparoscopic adhesiolysis and those having laparoscopy alone.
Adhesions may be caused by endometriosis, previous surgery or previous infection. Two distinct forms of adhesive disease are recognised: residual ovary syndrome (a small amount of ovarian tissue inadvertently left behind following oophorectomy which may become buried in adhesions) and trapped ovary syndrome (in which a retained ovary becomes buried in dense adhesions post-hysterectomy). Removal of all ovarian tissue or suppression using a GnRH analogue may relieve pain.
Symptoms suggestive of IBS or interstitial cystitis are often present in women with chronic pelvic pain. These conditions may be a primary cause of chronic pelvic pain, a component of chronic pelvic pain or a secondary effect caused by efferent neurological dysfunction in the presence of chronic pain.
Musculoskeletal pain may be a primary source of pelvic pain or an additional component resulting from postural changes. Pain may arise from the joints in the pelvis or from damage to the muscles in the abdominal wall or pelvic floor. Pelvic organ prolapse may also be a source of pain. Increasing interest is also being shown in trigger points – localised areas of deep tenderness in a tight band of muscle, the aetiology of which is not fully understood. It may relate to chronic contraction of the muscle, with the stimulus coming from misalignment of the pelvis or a discrete pain such as endometriosis. The pain from a trigger point may then become self-perpetuating. Clear evidence regarding diagnostic tests and therapeutic options is lacking.
Nerve entrapment in scar tissue, fascia or a narrow foramen may result in pain and dysfunction in the distribution of that nerve. The incidence of nerve entrapment (defined as highly localised, sharp, stabbing or aching pain, exacerbated by particular movements, and persisting beyond 5 weeks or occurring after a pain- free interval) after one Pfannenstiel incision is 3.7%.
Enquiry should be made regarding psychological and social issues which commonly occur in association with chronic pelvic pain; addressing these issues may be important in resolving symptoms. Depression and sleep disorders are common in women with chronic pain. This may be a consequence rather than a cause of their pain, but specific treatment may improve the patient’s ability to function. Similarly, women with chronic pelvic pain tend to suppress their unwanted thoughts and feelings either as a cause or consequence of their pain.
The relationship between chronic pelvic pain and sexual or physical abuse is complex. Women with chronic pain in general are more likely to report physical or sexual abuse as children than pain-free women. Those who experience chronic pelvic pain specifically are more likely to report sexual abuse than women with another chronic pain complaint.
The initial history should include questions about the pattern of the pain and its association with other problems, such as psychological, bladder and bowel symptoms, and the effect of movement and posture on the pain.
On taking the history, special note should be taken of any ‘red flag’ symptoms which may need further investigation and referral to a specialist.
If the situation allows, it may be helpful to ask directly about past or present sexual assault, particularly intimate partner violence.The doctor must be prepared to listen and accept these experiences as stated and know where to access specialist support.
Completing a daily pain diary for two to three menstrual cycles may help the woman and the doctor identify provoking factors or temporal associations. The information may be useful in understanding the cause of the pain.
Symptom-based diagnostic criteria can be used with confidence to make the diagnosis of IBS with a positive predictive value of 98%.
Continuous or recurrent abdominal pain or discomfort on at least 3 days a month in the last 3 months, with the onset at least 6 months previously, associated with at least two of the following:
Symptoms such as abdominal bloating and the passage of mucus are commonly present and are suggestive of IBS. Extraintestinal symptoms such as lethargy, back ache, urinary frequency and dyspareunia may also occur in association with IBS.
Diagnostic laparoscopy has been regarded in the past as the ‘gold standard’ in the diagnosis of chronic pelvic pain. It may be better seen as a second-line investigation if other therapeutic interventions fail.
Diagnostic laparoscopy is the only test capable of reliably diagnosing peritoneal endometriosis and adhesions. Gynaecologists have therefore seen it as an essential tool in the assessment of women with chronic pelvic pain. However, it carries significant risks: an estimated risk of death of approximately 1 in 10 000, and a risk of injury to bowel, bladder or blood vessel of approximately 2.4 in 1000, of whom two-thirds will require laparotomy.
One-third to one-half of diagnostic laparoscopies will be negative and much of the pathology identified is not necessarily the cause of pain.
Women with cyclical pain should be offered a therapeutic trial using hormonal treatment for a period of 3–6 months before having a diagnostic laparoscopy.
Women with IBS should be offered a trial with antispasmodics.
Women with IBS should be encouraged to amend their diet to attempt to control symptoms.
Women should be offered appropriate analgesia to control their pain even if no other therapeutic manoeuvres are to be initiated. If pain is not adequately controlled, consideration should be given to referral to a pain management team or a specialist pelvic pain clinic.
Ovarian suppression can be an effective treatment for cyclical pain associated with endometriosis. The effect can be achieved with the combined oral contraceptive, progestogens, danazol or GnRH analogues, all of which are equally effective but have differing adverse effect profiles.