Gab Kovacs1 and Paula Briggs2
(1)
Department of Obstetrics and Gynaecology, Monash University, Clayton, Victoria, Australia
(2)
Sexual and Reproductive Health, Southport and Ormskirk Hospital, Southport, UK
Definition
Incidence
Aetilogy and Pathogenesis
Clinical Assessment
History
Examination
Investigations
Treatment
Medical
Surgical
Complications: Subfertility
Prognosis
Definition
Endometriosis is the growth of endometrial tissue outside the uterine cavity.
· Endometriosis interna is within the wall of the uterus – also known as adenomyosis
· Endometriosis externa is outside the uterus – the pelvic wall, the Pouch of Douglas and the ovaries (called endometriomata) are the commonest sites, but deposits of endometriosis can be anywhere, including the lungs and brain!
Incidence
The true incidence of endometriosis is not known.
· It is often associated with subfertility
· It is more common in the 20s and 30s
Aetilogy and Pathogenesis
There are several theories for the aetiology:
· Retrograde spread of menstruation
· Coelomic metaplasia
· Lymphatic spread
· Vascular spread
· But no-one actually knows
The common factor is thought to be a change in immunological tolerance, where the ectopic endometrium is not attacked by the immune system.
The way that endometriosis interferes with fertility is not well understood. The pathogenesis is thought to be through the excessive release of prostaglandins, which in turn interfere with fertilisation and implantation.
Clinical Assessment
History
The most common symptom of endometriosis is pain. Classically this increases as menstruation progresses (in contrast to spasmodic dysmenorrhoea which is at its worst just before the start of, and on the first day of menstruation). The degree of pain is not helpful. Often women with severe endometriosis have minimal pain, whereas some women with minimal endometriosis report debilitating pain, that is not relieved by over-the counter pain medications and prevents them from performing daily activities.
Pelvic pain resulting from endometriosis is not restricted to menstruation. The site of the endometriotic deposits can determine the nature of the pain experienced. For example, endometriosis in close proximity to the bowel can result in pain on defaecation (dyschezia), deposits in the Pouch of Douglas may result in pain during sexual intercourse (deep dyspareunia) and deposits in and around the bladder can cause dysuria and cyclical haematuria.
The pain often radiates through to the back and down the legs.
It may be associated with pre-menstrual spotting, diarrhoea, nausea or vomiting.
A significant number of women with endometriosis will present with heavy menstrual bleeding (HMB). Many women who complain of HMB will have undiagnosed endometriosis. Where there is a suspicion that there may be underlying endometriosis, it is reasonable to undertake a therapeutic trial (see below) as definitive invasive investigations have an element of risk associated with them.
Examination
· Abdominal examination may reveal nothing to assist with the diagnosis.
· Speculum examination can occasionally reveal endometriotic deposits in the vagina or on the cervix.
· Bimanual examination may detect nodules in the Pouch of Douglas and possibly enlargement and/or tenderness of the ovaries if endometriomata are present. The uterus may be enlarged and/or tender. A retroverted uterus, especially if “fixed” may indicate adhesions in association with endometriosis in the Pouch of Douglas.
Investigations
· Biochemistry – whilst CA125 is often elevated in endometriosis, it is not diagnostic. There are other causes for a raised CA 125, especially epithelial ovarian tumours, although the levels seen in association with ovarian cancer are often significantly higher than those seen in association with endometriosis.
· Ultrasound – this is best performed transvaginally and is only really helpful in detecting endometriomata (chocolate cysts). Other endometriotic deposits are not detected using ultrasound, although it may be possible to detect adhesions.
· The “gold standard” for diagnosing endometriosis is to visualise it laparoscopically and then confirm it by biopsy and histology. However not all suspected areas of endometriosis are positive on biopsy and some types of endometriosis are difficult to detect visually.
· Endometrial histology with special stains – there is some early work suggesting that the detection of nerve fibres within the endometrium (between the basal and stromal layer) may be suggestive/diagnostic of endometriosis. However this still needs to be confirmed by further studies.
· Staging – a number of scales for staging endometriosis have been described.
The following is recommended (Fig. 8.1):
Fig. 8.1
Staging of endometriosis
· Stage 1 (minimal)
Stage 1 endometriosis is classified as minimal, as there are only a few small isolated patches of tissue growing outside of the uterus. These deposits are often located on the peritoneum.
· Stage 2 (mild)
Stage 2 endometriosis is considered mild and is usually diagnosed when there are several small patches of endometriosis, a few of which are associated with areas of adhesions or scar tissue. These deposits, as with minimal disease are often located on the peritoneum.
· Stage 3 (moderate)
In stage 3 endometriosis there are areas of both superficial and deep disease. There are usually several well defined areas of adhesions or scar tissue. This stage commonly involves endometriomata (chocolate cysts).
· Stage 4 (severe)
Stage 4 endometriosis is the most severe. Women have both superficial and deep disease associated with adhesions and may also have involvement of the bowel and other organs.
Treatment
Medical
Hormonal
· Withdrawl of oestrogen – Under the influence of oestrogen the endometrium proliferates. The same process occurs within endometriotic deposits. Consequently, if the circulating level of oestrogen decreases, the endometriotic deposits regress.
· The use of GnRH agonists to suppress the secretion of gonadotrophins will achieve this, but at the price of side effects of oestrogen deprivation (menopausal symptoms).
· Administration of progestogen. Progestogens suppress the endometrium and can be used to treat endometriosis. This requires long term administration.
· Desogestrel progestogen only pills result in anovulation and this eventually results in amenorrhoea in most women. Unscheduled bleeding in the intervening period can result in discontinuation of treatment before the desired effect can be achieved.
· Medroxyprogeterone acetate can be provided orally or used in depot form to achieve anovulation and amenorrhoea (Depoprovera®). Like the POP, the depot product is licensed for contraception, but it is also recommended (but not licensed) to manage heavy menstrual bleeding (NICE Clinical Guideline 44), a common presenting complaint in women with endometriosis.
· Dienogest, marketed as Visanne®, is an orally active progestin licensed to treat endometriosis and approved in the European Union, but not available in the UK. It has been shown to be as effective as a GNRH analogue in treating endometriosis..
· The use of combined hormonal contraception (CHC) – pills, patches and rings, results in an inactive endometrium with few glands. Omitting the hormone free interval with any one of these products, reduces potential bleeding and will result in an improvement in control of symptoms related to endometriosis in some women.
Other Medical
In women with mild symptoms of endometriosis, even without a definitive diagnosis the use of simple analgesics, antispasmodics and non-steroidal anti-inflammatory drugs may be sufficient to control symptoms.
· A new class of drug known as selective progesterone receptor modulators look promising as a treatment option for endometriosis. This class of drug is already used as a method of emergency contraception in a stat dose and more recently as a treatment to shrink uterine fibroids. Notably women using this treatment, marketed as Esmya®, become amenorrhoeic, and logically this would be helpful in reducing and controlling symptoms associated with endometriosis.
Surgical
· Minor – this involves laparoscopic excision or ablation of endometriotic lesions. Care has to be taken not to damage underlying structures, especially the ureter.
· Major – this may require extended surgery for extensive endometriosis possibly involving the bowel or bladder. This type of surgery is difficult and time consuming and women with severe disease are better managed by tertiary referral to a sub-specialist.
Total hysterectomy including removal of the ovaries (pelvic clearance) (TAHBSO) is sometimes necessary in an attempt to manage chronic pelvic pain associated with endometriosis. However, such radical surgery is avoided where possible.
Complications: Subfertility
The association between endometriosis and subfertility is well recognised, but the mechanism is poorly understood.
Prognosis
During the reproductive years endometriosis is a recurring disease. Treatment depends on the severity of the disease and an attempt is made to avoid radical surgery if possible. However, a small number of women may require surgical intervention in order to improve their quality of life. Following pelvic clearance, hormone replacement therapy will be required and the possibility of residual endometrial deposits should not be forgotten. Despite removal of the uterus, endometrial protection should be provided in order to prevent endometrial hyperplasia in any deposits of endometriosis not removed at the time of surgery.
Once a woman reaches the natural menopause, and circulating oestrogen levels are insignificant any remaining deposits of endometriosis are likely to resolve.