Ultrasound of the Uterus and Endometrium

Evaluating Abnormal Bleeding: Endometrial Biopsy vs. Endovaginal Ultrasound

In those patients who present with abnormal bleeding, it's worth considering whether the step obtained should be an endometrial biopsy or endo vaginal ultrasound.

This comes into particular play when evaluating women with postmenopausal bleeding. Remember that most causes of postmenopausal bleeding are benign, in particular endometrial atrophy, but the differential diagnosis includes other processes including cancer.

In general, according to the literature, the risk of endometrial cancer as a cause of postmenopausal bleeding ranges from seven to 30%. That risk goes up with patient age, obesity, and a history of diabetes. And you will read different algorithms. Propo, which pro, are proponents of initial evaluation by means of tissue sampling versus ultrasound imaging.

When Should the Endometrial Biopsy Be Done First?

Well, it's considered the gold standard and in many minds the best first step. It's performed in all patients with postmenopausal bleeding unless there's a recent initiation of hormone replacement therapy. That's the guideline proposed by the gynecologists with whom we work.

It's also performed in women 35 to 40 years old with the persistent irregular bleeding, meaning three months or more of symptoms, and sometimes in younger women if there's increased risk in particular obesity or chronic and ovulation. It's also suggested that biopsy performed if be performed if there is persistent abnormal bleeding despite medical therapy.

When and Why Might Endovaginal Ultrasound Be Used Instead?

Well, ultrasound evaluates the thickness of the endometrial stripe directly. It can be used in those settings where the cervix is stenos and a biopsy cannot be performed, and it can be helpful for anatomic lesions like those I showed earlier, polyps or submucosal myomas, which may result in false negative or misleading endometrial biopsy results.

A conventional ultrasound may be followed by sonohysterography when using ultrasound in the workup of postmenopausal bleeding. It's worth remembering that an endometrial thickness less than five millimeters virtually excludes endometrial cancer, and in that way, we play a role in the evaluation.

Ultrasound is not as helpful in evaluating premenopausal or perimenopausal women with abnormal bleeding. Keep in mind the utility of the appropriate timing of the exam. We'll discuss tamoxifen later. Worth mentioning here that ultrasound is often not useful for evaluating women on tamoxifen.

And we were reiterating if that the results are negative on biopsy and ultrasound, but a patient has persistent bleeding, she needs additional workup.

Normal Appearance of the Postmenopausal Endometrium

If we are going to use ultrasound to evaluate postmenopausal bleeding, we have to review first the normal appearance of the postmenopausal endometrium. Once women have stopped cycling, the endometrium should be a consistent uniform thin echogenic line, less than eight, usually less than five millimeters in AP diameter.

If there is a small amount of intrauterine fluid, it should not be included in the measurement reported. In those instances, a single layer can be seen that should be no thicker than three millimeters. These measurements are best done on an endo vaginal rather than a transabdominal view.

Potential Pitfalls in Endometrial Thickness Measurement

And a few words about potential pitfalls in this measurement. The image obtained from which the endometrial thickness is measured by convention is the sagittal plane. What should be measured and reported is the site of maximal endometrial thickness, usually near the fundus.

The thickness involves both the front and back layers, a bilayer thickness not to include the inner myometrium, which is usually hypoechoic compared with the echogenic endometrium. As I said, if there is intrauterine fluid, it should not be included in the measurement, and it might interest you to know that the inter observer variation in these numbers is about 1.5 millimeters.

Here are four sagittal endo vaginal views of women with abnormal bleeding in which the endometrial thickness is measured. Keep in mind that the uterus is broader than it is in the AP plane. Thus, if different thicknesses are obtained, it is possible that rather than scanning in the pure sagittal plane, some coronal images were obtained. Also, focal endometrial abnormalities may result in different numbers in the course of the exam.

While we don't measure the endometrial thickness on the axial view, some images in that plane are helpful to recognize those possibilities.

Technical Errors and Review Findings

We were a center that reviewed endometrial thickness measurements performed at a bunch of different centers across the us And, in our review of those exams, we realized that a common technical error was inappropriate depth settings when measuring the endometrium. The depth of the image should be appropriate for the size of the uterus to ensure optimal visualization and most reliable measurement of the endometrium.

We also participated in a meta-analysis looking at the reliability of the cutoff for endometrial Thickness and came up with this message based on that review. For a postmenopausal woman with vaginal bleeding, with a pretest probability of cancer of approximately 10%, and endometrial thickness of five millimeters or less by ultrasound resulted in a post-test probability of cancer of 1%, significantly reducing the risk by seeing a uniform thin endometrium less than five, and is as is often seen in these women with postmenopausal bleeding, a markedly thin endometrium and atrophic endometrium measuring only 1.4 millimeters associated with postmenopausal bleeding.

Advantages of Ultrasound

The advantages of ultrasound in this regard is it's less invasive than endometrial biopsy. It's nearly pain-free and well tolerated in women even of advanced age. It can obviate the need for biopsy if normal, if thin, as was the case here. Importantly, it's diagnostic in women with cervical stenosis who cannot undergo effective biopsy. The accuracy is similar to that reported for endometrial biopsy and the cost compares favorably.

Post-Biopsy Ultrasound Considerations

Sometimes we encounter women in whom a biopsy has been performed or attempted, and in those instances, it's worth remembering that there will be some intary blood making the ultrasound less reliable. If women undergo a biopsy, I would recommend you wait at least a week before performing an endo vaginal ultrasound to assess the endometrium.

Consensus Panel and Cost-Effective Approaches

The Society of Radiologists in ultrasound convened a consensus panel several years ago, addressing several questions related to the evaluation of women with postmenopausal bleeding. The take home message from that panel included this statement, either ultrasound or biopsy could be used safely and effectively as a first diagnostic step.

And there are different approaches even within our own institution to this evaluation. When looking at a cost effective decision making, one again could start with biopsy or ultrasound. It's worth incorporating into that assessment, the pretest probability of cancer and patient's risk factors.

If the prevalence of endometrial cancer based on risk factors was over 15%, then biopsy was the most cost effective first step. And alternatively, based on risk factors, if the prevalence of cancer was less than 15%, ultrasound first most cost effective.