The role of transvaginal ultrasound and sonohysterography in the evaluation of postmenopausal bleeding.

P ostmenopausal bleeding is a common complaint, with most cases caused by benign etiologies such as fibroids, endometrial polyps, or atrophy. Endometrial cancer is a relatively rare cause of abnormal bleeding, estimated to account for 10% of postmenopausal bleeding. Nonetheless, abnormal uterine bleeding is the most common presentation of endometrial cancer. Timely diagnosis of cancer is imperative because early detection and treatment are associated with higher disease-free survival and lower morbidity. Radiologists and gynecologists are often faced with a wide array of diagnostic tools in the evaluation of postmenopausal bleeding, including transvaginal ultrasound (TVUS), endometrial biopsy, saline infusion sonohysterography (SIS), dilation and curettage, and hysteroscopy. What would be an efficient, cost-effective, and patient-friendly diagnostic approach without missing cancer? This has been the subject of much research. In this month’s issue, Skaznik-Wikiel et al examined 135 women with nonmalignant causes of postmenopausal bleeding who received both TVUS and a Breference standard[ SIS. They found that using an endometrial echo cutoff of less than 5 mm on TVUS, the sensitivity for detecting benign intracavitary lesions was 76%, specificity was 63%, positive predictive value was 67%, and negative predictive value was 72%. For every four women who had an endometrial thickness of less than 5 mm, one had an endometrial polyp or leiomyoma not detected by TVUS. Eighty-four (61.3%) women in their study population had an endometrial biopsy, and histologic diagnosis included 78.6% with proliferative endometrium, 15.5% with atrophic endometrium, 4.8% with endometrial polyps, and 1.2% with endometrial hyperplasia without atypia. The authors conclude that there is no endometrial thickness value cutoff under which benign endometrial pathology could be ruled out, and additional investigation of the intrauterine cavity should be used. Their findings echo previous reports stating that SIS outperforms TVUS in detecting intracavitary abnormality. TVUS and SIS play different roles in the diagnostic algorithm of postmenopausal bleeding; the former is used for screening cancer, which is most commonly a diffuse process, and the latter is used for diagnosing focal, probably benign causes of bleeding. Because cancer is the only cause of vaginal bleeding that is potentially lethal, the primary goal in the workup of abnormal bleeding is to exclude malignancy. TVUS is a well-tolerated, inexpensive way to initially screen for endometrial cancer. With an endometrial thickness cutoff of 5 mm or greater considered abnormal, TVUS is the most sensitive modality for detecting endometrial cancer (96% sensitivity), better than nonfocal biopsy (87% sensitivity), sonohysterography (89% sensitivity), or hysteroscopy (86% sensitivity). For a postmenopausal woman with vaginal bleeding and a 10% pretest probability of endometrial cancer, her probability of having cancer is 1% after a normal TVUS result. For symptomatic postmenopausal women, a thickness of less than 5 mm indicates that bleeding is probably secondary to atrophy or other focal abnormalities. Exception should be made for women receiving tamoxifen, in whom endometrial thickness measurements are less useful in assessing endometrial pathology. Abnormalities such as endometrial polyp and carcinoma often coexist. Furthermore, subendometrial cystic changes caused by tamoxifen may simulate endometrial thickening on TVUS. In these cases, SIS may be helpful in separating subendometrial from endometrial pathology. As histology constitutes the definitive diagnosis, an alternate strategy for cancer screening in the workup of postmenopausal bleeding is blind endometrial biopsy. It has a high rate of inadequacy of sampling, often necessitating performance of other examinations such as SIS or hysteroscopy. However, when separating endometrial cancer from nonmalignant causes of postmenopausal bleeding, endometrial biopsy performs well. Whether sonography or endometrial biopsy is used initially depends on the physician’s assessment of the woman’s risk, the nature of the physician’s practice, the availability of high-quality sonography, and the woman’s preference. From an economic perspective, Medverd and Dubinsky found that, at a combined endometrial carcinoma/atypical adenomatous hyperplasia prevalence of 10%, diagnostic pathways initiated with TVUS bring savings of up to 16% over pathways initiated with endometrial biopsy. If the pretest probability of cancer is higher in certain populations, then it may make both clinical and economic sense to perform nonfocal biopsy as the initial screening test. For instance, biopsy should be considered for women receiving tamoxifen with abnormal uterine bleeding, regardless of endometrial thickness, because of a higher rate of cancer among these women. Only after cancer has been deemed unlikely, either by lack of the woman’s risk factors, normal endometrial thickness with TVUS, or a negative nonfocal endometrial biopsy, should