IMAGING FEATURES OF ADENOMYOSIS

Dr Denise Ladwig B.MED MRANZCOG DDU, Fellow Medical Imaging, Royal Hospital for Women, Randwick NSW 2031

Abstract
This review focuses on the imaging modalities available for the diagnosis of adenomyosis. Accurate diagnosis is essential for optimal management of patients. Adenomyosis is a common gynaecological condition, and both sonographers and sonologists should be familiar with the characteristic imaging features. Symptoms are non-specific and not helpful in diagnosis.

Introduction
Adenomyosis is a common benign gynaecological condition. Rokitansky1 first described the condition in 1986. It is characterized by the presence of heterotopic endometrial glands and stroma within the myometrium, with secondary smooth muscle hypertrophy and hyperplasia2. It is unclear why smooth muscle changes are associated with the ectopic endometrium3. Imaging plays an important role in the diagnosis of adenomyosis. Clinical diagnosis can be difficult. Adenomyosis may be suspected in less than half of patients undergoing hysterectomy4. The signs and symptoms of adenomyosis are non-specific. Adenomyosis may present with menorrhagia, dysmenorrhoea, pelvic pain and infertility5. It may also be asymptomatic. The severity of symptoms correlates roughly with the extent of the disease. The precise cause of menorrhagia is unknown. The uterus affected by adenomyosis may have poorer contractility. Prostaglandins may also play a role, as administration of mefenamic acid reduces blood loss6. Adenomyosis may coexist with uterine myomas (19 – 56%), endometriosis (6 - 20%) and endometrial hyperplasia (6 – 43%)7. There is also an increased risk of endometrial adenocarcinoma8. Endometrial ablation is more likely to fail in the presence of adenomyosis. There are currently no diagnostic serum markers, although CA125 has been suggested as a screening technique9.

Adenomyosis is commonly diffuse, although focal deposits also occur. In generalized adenomyosis, adenomyotic deposits are distributed widely throughout the uterus, typically commencing in the uterine fundus and then progressing towards the cervix. As myometrial involvement increases, the uterus gradually enlarges. The uterine contours and endometrial cavity are usually not deformed. Focal deposits of adenomyosis are known as adenomyomas. They are circumscribed nodular aggregates of smooth muscle and endometrial glands. Adenomyomas may be single or multiple. Adenomyomas must be distinguished from leiomyomas, which consist of bundles of smooth muscle cells arranged in an interlacing pattern. The distinction may become extremely important in decisions regarding clinical management. Surgical removal of an adenomyoma is extremely difficult or impossible, as there are no planes of cleavage with respect to the myometrium. The definitive surgical treatment for adenomyosis is usually hysterectomy. Leiomyomas compress the surrounding tissue, forming a pseudocapsule. They may be surgically removed (myomectomy), particularly if conservation of fertility is desired.

The pathogenesis of adenomyosis is poorly understood, with numerous theories proposed. Invagination of the basalis endometrium into the myometrium is currently favoured6; de novo development of adenomyosis from Müllerian rests in an extrauterine position is also a possible explanation. The trigger for such invasion or transformation remains unknown. Hyperestrogenism and impaired immune-related growth control in the ectopic endometrium may contribute. Adenomyosis usually atrophies after menopause.

The exact incidence of adenomyosis is uncertain. Adenomyosis is fundamentally a histopathologic diagnosis. Adenomyosis is reported to occur in 5– 70 % of hysterectomy specimens5. The incidence is dependent on the histological criteria used, the selection of specimens evaluated, and the thoroughness of pathologic examination. Adenomyosis is found in 10-50% of postmortem examinations. Benson and Sneeden10 suggested that the endometrium must extend from the basalis into the myometrium by at least 2 low-power fields (8mm). Bird et al.11 found adenomyosis in 61.5% of 200 consecutive hysterectomies, although half their cases occurred less than one low-power field below the basal endometrium.

Citation
Ladwig D. Imaging features of adenomyosis. ASUM Bulletin 2002.3:6-10.