One of the most common disorders evaluated by gynecologists is unexpected or excessive uterine bleeding. It should be emphasized that only 10% to 15% of postmenopausal women who present with postmenopausal bleeding have endometrial cancer; the vast majority have bleeding secondary to benign disorders such as atrophy or hyperplasia.2 The role of sonography is to determine which patients can forgo endometrial biopsy and to monitor endometrial changes in patients receiving tamoxifen or other forms of hormone replacement therapy (HRT). Approximately 30% of women receiving combined HRT experience bleeding. It is the role of TVS to determine which patients need biopsy, dilatation and curettage, alteration in their medicines, or observation.
Although endometrial cancer is more common than ovarian cancer, this disease is associated with far less mortality. This is clearly related to the fact that one of the earliest signs of endometrial cancer is vaginal bleeding. In addition, endometrial cancer is usually still confined to the uterus when the patient presents, whereas two-thirds of patients with ovarian cancer have extensive disease at time of presentation (see Chapter 35 on early detection of ovarian and endometrial cancer).
It is important conceptually to differentiate causes of uterine bleeding in the premenopausal from the peri- or postmenopausal woman. In the woman of child-bearing age, bleeding is usually associated with anovulatory cycles. This is typically related to poor corpus luteum function and support of endometrium with progesterone. Fibroids are also a very common cause of bleeding in this age group. It is thought that fibroids may denude the endometrial surface, resulting in excessive bleeding. Postmenopausal women have bleeding due to a variety of disorders. These include atrophy, hyperplasia, polyps, cancer, and fibroids. Atrophy is the most common cause of bleeding and is related to excessive thinning of the endometrium, making it friable and prone to bleeding. Sonographic detection of a polyp by TVS with or without SHG enables its hysteroscopic removal and cure of bleeding. Conversely, endometrial biopsy is sufficient if the endometrium appears diffusely thickened on SHG.
Approximately 30% of patients who receive HRT may experience bleeding during the first few months of treatment. It is also not uncommon for some patients who receive cyclical HRT to have bleeding in days 12 to 14 of the pseudocycle related to decreasing amounts of progesterone. Bleeding outside of these times can be associated with endometrial pathology. Transvaginal sonography can help assess the endometrium for abnormal thickness and/or texture in these patients.
Endometrial evaluation by TVS is helpful in patients undergoing tamoxifen treatment because this medication is associated with an increased risk of hyperplasia and cancer. However, not all patients with thickened endometrium on TVS will have positive biopsies. This may be attributed to a sampling error or the fact that cystic atrophy of the endometrium can produce multiple interfaces that appear to thicken the sonographic depiction of the endometrial "stripe." In addition, tamoxifen exposure may be associated with the development of punctuate cystic areas in the inner myometrium, thought to represent reactivated adenomyosis.3
Recently, three-dimensional (3D) sonography has provided a means to better visualize the entire endometrium due to its ability to depict it in a coronal plane. Three-dimensional ultrasonography (US) can be performed using a freehand sweep or, better, with an automated sweep transducer. With either technique, multiplanar images are obtained including one in the coronal plan. The angle of the scan plane can be altered to best depict the entire endometrial width. For a more detailed discussion of 3D US in gynecology, please refer to Chapter 47.