Adenomyosis

A condition characterised by the presence of endometrial glands and stroma within the myometrium (the muscular uterine wall), producing uterine enlargement together with the characteristic symptom pattern of heavy menstrual bleeding and dysmenorrhoea.

It was historically diagnosed predominantly through histopathological examination following hysterectomy. It is increasingly recognised and diagnosed in symptomatic women of reproductive age through improved, non-invasive imaging techniques.

It is a distinct, though sometimes coexisting, condition from endometriosis, given that adenomyosis reflects ectopic endometrial tissue within the uterine muscle itself, in contrast to the extrauterine ectopic tissue characteristic of endometriosis.

Pathophysiology

• The underlying mechanism is believed to reflect direct invasion of endometrial tissue into the myometrium, potentially reflecting disruption of the normal junctional zone (the interface between the endometrium and myometrium) through mechanisms including previous uterine surgery, instrumentation, or childbirth.
• A proportion of cases occur without any clearly identifiable, specific preceding event.
• The ectopic endometrial tissue within the myometrium responds to cyclical hormonal fluctuation in a manner analogous to normal endometrium, with associated localised bleeding and inflammation.
• Reactive myometrial hypertrophy surrounds the ectopic glandular tissue, producing the characteristic, diffuse uterine enlargement and, on imaging, the characteristic pattern of myometrial thickening.
• Adenomyosis may be diffuse (affecting the myometrium relatively uniformly throughout the uterus) or focal (localised to a specific region).
• Focal disease sometimes produces a discrete mass, termed adenomyoma, which can present a diagnostic challenge in distinguishing from uterine fibroids on imaging or clinical assessment.

• Heavy menstrual bleeding and progressively worsening, severe dysmenorrhoea represent the characteristic, classic symptom pattern. Symptoms are typically most prominent in women in their late thirties to forties.
• The condition can affect women across a broader age range, including younger women, with increasing contemporary recognition given improved diagnostic imaging availability.
• Chronic pelvic pain, together with, in some women, deep dyspareunia, may accompany the classic symptom pattern.
• A substantial proportion of affected women, particularly those with more extensive disease, experience significant, cumulative impact on quality of life given the frequently severe, treatment-resistant nature of the associated symptoms.
• On examination, the uterus is frequently diffusely, symmetrically enlarged and tender, particularly around the time of menstruation. Examination findings can be relatively non-specific and are not required for diagnosis, which increasingly relies on the imaging approaches.
• A substantial proportion of affected women demonstrate coexisting endometriosis or uterine fibroids, reflecting some shared underlying risk factors and pathophysiological mechanisms.
• Careful, full assessment for these potentially coexisting conditions is relevant to full evaluation of a woman presenting with this symptom pattern.

• Transvaginal ultrasound, performed by an appropriately experienced practitioner, represents the standard, first-line imaging investigation.
• Characteristic sonographic features include asymmetric myometrial thickening, poorly defined margins between the endometrium and myometrium, myometrial cysts, and a heterogeneous myometrial echotexture, supporting diagnosis with reasonable sensitivity and specificity in experienced hands.
• Magnetic resonance imaging offers superior diagnostic accuracy, particularly valuable for distinguishing adenomyosis from uterine fibroids where this distinction remains uncertain on ultrasound.
• Magnetic resonance imaging also allows more detailed characterisation of disease extent and pattern (diffuse versus focal) where this information is relevant to treatment planning. The characteristic finding of a thickened junctional zone is a key, specific diagnostic feature on this modality.
• Definitive histopathological confirmation traditionally required hysterectomy specimen examination. This is no longer required for clinical diagnosis and management planning in contemporary practice, given the substantially improved diagnostic accuracy of modern, non-invasive imaging techniques.
• Hysterectomy is therefore reserved as a treatment option for confirmed or clinically suspected disease rather than representing a required diagnostic step.

• Medical management follows broadly similar principles to those used for endometriosis and heavy menstrual bleeding more generally. It comprises hormonal treatment aiming to suppress cyclical endometrial activity.
• The levonorgestrel-releasing intrauterine system is a particularly effective, commonly used first-line treatment option, given its combination of effective local progestogen delivery directly addressing both the heavy bleeding and, to a meaningful degree, the associated pain.
• Combined hormonal contraception and other progestogen-based treatments, together with nonsteroidal anti-inflammatory drugs for symptomatic pain relief and tranexamic acid for heavy bleeding specifically, represent further relevant medical treatment options.
• Gonadotropin-releasing hormone agonist or antagonist treatment, following similar principles to its use in endometriosis, represents an effective option for more severe symptoms not adequately controlled with the standard first-line approaches. It generally requires concurrent add-back hormone therapy where used for a prolonged duration.
• Uterine artery embolisation represents a uterus-preserving interventional treatment option for appropriately selected women, particularly relevant where fertility preservation is desired.
• The evidence regarding effectiveness specifically for adenomyosis is somewhat more variable compared with its more established role in uterine fibroid management.
• Hysterectomy represents definitive, curative treatment for women who have completed childbearing and whose symptoms are not adequately controlled with medical management, offering complete resolution of symptoms given removal of the entire affected uterus.
• Hysterectomy is an appropriate, reasonable option for appropriately counselled women with severe, treatment-refractory symptoms and no ongoing fertility desire.
• Full, individualised counselling regarding the range of available treatment options, incorporating the woman's specific symptom severity, fertility considerations, and personal preference, underpins full, patient-centred management of this increasingly recognised condition.
• Careful assessment for and management of any coexisting endometriosis or fibroid disease is also needed.