Endometrial tissue is that which lines the inside of the uterus, and which bleeds approximately once a month during menstruation. Endometriosis is a condition in which a piece of endometrial tissue has travelled out of the uterus and implanted in a place it ought not to be. Adenomyosis, on the other hand, is where the endometrial tissue spreads directly into the muscle of the uterus – the name refers to the glandular tissue of the endometrium invading the muscle. Both conditions can lead to painful menstruation and irregularly heavy or frequent periods, although some individuals will have no symptoms whatsoever. While endometriosis can be treated using hormones and by destruction of the errant tissue, adenomyosis is currently thought to only be curable by hysterectomy.

Cause

In the case of endometriosis, the menstrual cycle appears to be to blame. In each cycle in which the ovum is not fertilised, the endometrial lining of the uterus is shed. While the bulk of this shed lining leaves via the vagina, most women are thought to also lose a little through the Fallopian tubes¹. Contrary to popular perception, the tubes are not superglued onto the ovaries; as a result, some blood and endometrial tissue can escape into the abdominal cavity. These little bits of the lining of the uterus commonly end up resting on the outer surfaces of the ovaries, uterus, colon, rectum, and bladder, though they have been known to head as far afield as the umbilicus².

Once a piece of endometrium has come to rest, it may form a small cyst into which it bleeds each month. Continued cycles of bleeding and reabsorption cause the cyst to slowly enlarge as it fills with thickened blood; the dark brown colour of this blood means developed patches of endometriosis are often referred to as 'chocolate cysts'. The ability of endometrial tissue to survive where it shouldn't is not properly understood, though it may involve a defect in the process by which errant tissue is normally destroyed by white blood cells. Equally, it is not understood why in half of all cases the errant tissue later dies off for no apparent reason. It is clear, however, that the endometrial tissue requires a regular cycle of oestrogen – for this and other reasons, endometriosis is less likely to be a problem during pregnancy.

Meanwhile, adenomyosis is due to a direct spread of endometrial cells into the muscular wall of the uterus (the myometrium). These cells tend to come from the base of the endometrium; as a result, they are less sensitive to the hormonal cycle, and adenomyosis does not feature the chocolate cysts of endometriosis. Instead, the presence of endometrial cells in the myometrium triggers a growth of connective tissue and muscle around the site, leading to the slow growth of an 'adenomyoma'. Symptoms may take years to develop, and thus older women are more likely to be affected.

Symptoms

• Pain. As mentioned, both conditions can cause pain. In endometriosis this pain is cyclical, starting a few days before menstruation and peaking towards the end of the period. The pain is often felt in the lower abdomen, but may be quite vague and can vary depending upon the location of the cyst. In some cases the cyst may be quite large, leading to constant pain that worsens upon menstruation. The pain in adenomyosis tends to be like this, and worsens over time. Endometriosis involving the gut may lead to pain that alters with bowel motions, or may cause pain on defecation. If a cyst occurs in the 'pouch of Douglas³.' between the uterus and rectum, there may also be pain on intercourse (dyspareunia).

• Irregular periods. Both conditions can cause premenstrual spotting of blood, heavy periods, and an increase in the frequency of periods.

• Infertility. While both conditions are associated with decreased fertility, not all women with the conditions suffer from problems with fertility, and endometriosis is very much in the small print compared to other causes of infertility.

Treatment

Endometriosis can be suspected on the basis of symptoms, but can only be properly confirmed by laparotomy or laparoscopy⁴. The simplest treatment of symptomatic endometriosis is a combination of a painkiller and the oral contraceptive pill, the latter because it helps suppress oestrogen production and thus reduces the ability of errant endometrial tissue to survive. Other hormones may also be used to this end in women who do not wish to become pregnant, and include danazol, gestrinone, medroxyprogesterone acetate, and GnRH agonists. Needless to say these drugs interfere with the various effects oestrogen has on the body, and may lead to amenorrhoea⁵, weight gain, bone loss, voice deepening, acne, oily skin, mood disturbances and hot flushes depending upon the drug used. The effect of the treatment is determined by a second laparoscopy: around a third of women experience complete regression, but one in ten find that there is no change, regardless of whether the symptoms were being adequately treated.

Surgery may also be used to treat endometriosis: small areas may be burnt away using the electric current from a diathermy device, whereas large cysts require a greater degree of treatment. The nature of an individual woman's treatment depends upon a number of factors, including the site of disease, how severe it is, and whether she intends to have children. While women who do not intend to become pregnant may opt for a total hysterectomy and oopherectomy⁶, those who wish to retain their fertility require more conservative surgery, especially in cases where a cyst is present on an ovary.

Adenomyosis does not usually respond well to hormonal treatment, and a curative hysterectomy is usually offered if the woman is experiencing symptoms.

Prognosis

As mentioned above, hormonal treatment of endometriosis is more effective in some women than in others, and in some cases the symptoms may be treated without actually affecting the size of the cyst. Surgery tends to be more effective, though this depends upon the individual case. It is worth noting that endometriosis can recur despite successful treatment, and is more likely to do so if the original disease was widespread. Both endometriosis and adenomyosis can be upsetting for the individual and variable in their nature, and so it is best to clear up any doubts regarding prognosis with a good gynaecologist.