Four to fifteen out of a hundred women between the ages of 18 and 55 are affected by chronic pelvic pain. This is when internal pain occurs below the belly button for at least six months, though for many women the pain has been there for a lot longer. Chronic pelvic pain may be caused by a few different conditions, but in many cases, it is due to abnormal function of the nervous system, and called “neuropathic pain”. This is when constant pain in the pelvis, for example, pain arising from endometriosis, sensitises the nerves so that even non-painful stimuli (such as sitting down) become unbearable.
In a proportion of women with chronic pelvic pain, the pelvic floor muscles themselves are overly tight (or ‘spastic’). During a physical examination, your gynaecologist may feel thick and bulky bands of muscle on either side of the vagina. Though the reasons why this happens in some women is not clear, one theory is that the body tries to protect itself from the constant pain in the abdomen or genitals by clenching the pelvic floor muscles. The sensitised nerves contribute to this problem by making the muscles more ‘twitchy’ and prone to spasm. However if the muscles are forced to contract all the time, it can be very difficult for the muscles to fully relax, even after the source of pain is removed. The sensitised nerves and contracted pelvic muscles remain, and start to generate their own pain. This kind of pain is notoriously difficult to treat, and there is currently no perfect solution or objective way of assessing how treatments affect the muscles themselves.
Researchers at Alana have been collecting images of the pelvic floor muscles of 1,000 women at rest and under stress, in order to better understand the causes and effects of pelvic pain and come up with better treatments. A three-dimensional (3D) ultrasound machine uses a sensitive probe that sits just on the skin of the vulva (the skin around the vagina) and collects information on the muscles 2 to 3 centimetres underneath the skin. It almost allows us to put on X-ray goggles and see through the skin at the muscles beneath – in real time. We expect to find that the muscles are bulkier and stiffer than usual in women with pain.
So far, we have scanned 663 women visiting Alana Healthcare for Women with different combinations of pain symptoms and from a large range of ages. From the images, we’ve been able to measure the dimensions of the muscles using computer software to calculate the average width and length of the muscles, as well as visualise any injuries to the muscles themselves. Importantly we also asked each patient facts about themselves that may affect their muscles, such as previous pregnancies and births and past surgeries in the abdomen and pelvic floor, as well as concurrent conditions like endometriosis, pelvic floor prolapse and back pain.
If 3D ultrasound can accurately pick up bulky pelvic muscles in patients with chronic pelvic pain, treatments such as injections to the pelvic floor can then be given to relax the contracted muscles and interrupt the cycle of pain. Another use of the 3D ultrasound is to guide the injections into the pelvic floor. This is the second part of this study, which will assess if using 3D ultrasound guided injections to the pelvic floor improves how effective the treatment is at relieving pain. We expect that the accuracy offered by visualising the target muscles will have an edge over conventional methods where the surgeon locates the spasmed muscles using his or her finger. For the patient, this could mean longer lasting pain relief and reduced complications after the procedure. The surgeon also benefits with a reduced risk of sticking themselves with the needle!
Preliminary analysis of data from 228 women has confirmed the theories, with women with pain having a smaller pelvic opening and shorter pelvic floor muscles. However, a large proportion of the images have not yet been analysed and recruitment for the study is still ongoing (a big thank you to the ladies who’ve already participated!). 3D ultrasound has given doctors an objective way to assess pelvic floor muscles in women with pain, and will hopefully illuminate how chronic pain affects the body. We are excited about the potential uses for this technology and look forward to sharing the results from the final group.
References
- Zondervan, K. T., et al. (1999). “Prevalence and incidence of chronic pelvic pain in primary care: evidence from a national general practice database.” BJOG: An International Journal of Obstetrics & Gynaecology 106(11): 1149-1155. (http://onlinelibrary.wiley.com/doi/10.1111/j.1471-0528.1999.tb08140.x/full)
- Grace, V. M. and K. T. Zondervan (2004). “Chronic pelvic pain in New Zealand: prevalence, pain severity, diagnoses and use of the health services.” Australian & New Zealand Journal of Public Health 28: 369. (http://www.ncbi.nlm.nih.gov/pubmed/15704703)