Assessment of abnormal uterine bleeding: 3 office-based tools

Another investigation compared the sensitivity and specificity of TVUS and endometrial biopsy for the detection of endometrial disease in 448 postmenopausal women who took estrogen alone, cyclic or continuous estrogen-progesterone, or placebo for 3 years.⁹ Using a threshold value of 5 mm for endometrial thickness, TVUS had a positive predictive value (PPV) of 9% for detecting any abnormality, with 90% sensitivity, 48% specificity, and a negative predictive value (NPV) of 99%. Using this threshold, biopsies would be indicated in more than half of the women, of whom only 4% actually had serious disease.

Using a threshold thickness of 4 mm, Gull et al¹⁰ evaluated TVUS for the detection of endometrial cancer and atypical hyperplasia. For endometrial thicknesses exceeding 4 mm, TVUS had a sensitivity of 100%, specificity of 60%, a PPV of 25%, and an NPV of 100%. No woman with an endometrial thickness of 4 mm or less was found to have endometrial cancer.

Special considerations.

• Intracavitary fluid. On occasion, TVUS reveals “naturally occurring SIS”—that is, the spontaneous appearance of intracavitary fluid, which is probably secondary to cervical stenosis. (The name of this phenomenon refers to the iatrogenic fluid that is intrinsic to SIS.) Endometrial fluid also is observed in women who use tamoxifen, diethylstilbestrol, or megestrol acetate and in those who have a hematometra. In addition, about one quarter of patients with an endometrial malignancy have fluid in the endometrial cavity.¹¹

• Endometrial thickness. As noted, TVUS is excellent for ruling out endometrial abnormalities in postmenopausal patients because of the consistent thickness of the endometrium. When the endometrium is especially thickened, however, its usefulness is limited.

Observations in more than 5,000 women consistently note that an endometrium of less than 5 mm, measured as a double-layer, is most often associated with a pathology reading of “tissue insignificant for diagnosis”—hence atrophy.¹² When the endometrium is thicker than 5 mm, there is a greater chance of detecting polyps, endometrial hyperplasia, and endometrial cancer. Fewer than 0.12% of cancers were missed in this series.

When a skilled physician performs office hysteroscopy, the complication rate is less than 1%.

If the endometrium is thicker than 6 mm, then SIS or hysteroscopy is more helpful than TVUS in reaching a conclusive etiology for uterine bleeding. Further evaluation (hysteroscopy or SIS) is usually recommended when TVUS measurements of the endometrium are greater than 5 mm.¹³ Although a low cut-off, such as 4 mm or 5 mm, is associated with improved sensitivity, it sacrifices specificity.

TABLE 1

Transvaginal ultrasound: Endometrial thickness³²

Saline-infusion sonography

In SIS, saline is infused into the endometrial cavity during TVUS to enhance the view of the endometrium. This constitutes one of the most significant advances in ultrasonography of the past decade. SIS can provide a wealth of information about the uterus and adnexa in patients with abnormal bleeding. It offers an exquisite view of the endomyometrial complex that cannot be obtained with TVUS alone. It differentiates between focal and global processes and improves overall sensitivity for detecting abnormalities of the endometrium.

Although many terms have been used to describe this technique (echohysteroscopy, sonohysterosalpingography, and hydrosonography, to name a few), the term “saline-infusion sonography,” coined in 1996, most clearly describes the technique.¹⁴

Indications for use. SIS has been used to evaluate:¹⁵

• menstrual disorders
• endometrium that is thickened, irregular, immeasurable, or poorly defined on conventional TVUS, magnetic resonance imaging, or computed axial tomography studies
• midline endometrial echo with a thickness of more than 8 mm
• endometrium that appears irregular, bizarre, or homogeneous on TVUS in women using tamoxifen
• sessile and pedunculated masses of the endometrium that need to be differentiated
• findings with hysterosalpingogram
• recurrent pregnancy loss
• intracavitary fibroids before surgery to determine the depth of myometrial involvement and operative hysteroscopic resectability (see “Using saline infusion sonography staging to plan for fibroid surgery”)
• the endometrium after surgery

Complications are infrequent. The risk of infection is less than 1%. Practitioners should follow the same protocols for administering antibiotics as they do with hysterosalpingogram or other invasive endometrial procedures.

Possible problems during SIS include cervical stenosis, inability to distend the endometrium, uterine contractions, and heavy vaginal bleeding with resultant artifacts. There is also the risk of performing the procedure in early pregnancy, as well as the theoretic risk of disseminating endometrial cancer.

Sensitivity and specificity. Interpreting SIS images requires experience, correlation with the menstrual history, and careful scanning. In premenopausal women, SIS has an overall sensitivity of 94% and a specificity of 85%.⁸ In 1 review, its sensitivity for detecting endometrial polyps was 93%, and its specificity was 96%.⁸ In the detection of submucosal fibroids, it had a sensitivity of 94% and a specificity of 95%.⁸