Consider ultrasound first for imaging the female pelvis

Ultrasound technology has evolved dramatically in recent years and now includes applications such as 3-dimensional volume imaging, real-time evaluation of pelvic organs (simultaneous with the physical examination), and Doppler blood flow mapping without the need for contrast, which makes ultrasound imaging unique for imaging the female pelvis. Among the many cross-sectional imaging techniques, we should use the most informative, less invasive, and less expensive modality to avoid radiation when possible. Hence, ultrasound imaging should be the first imaging modality used in women with pelvic symptoms.

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Ever-present concerns regarding escalating health care costs and the appropriate use of medical technology demand careful choices regarding first-line medical diagnostic tests to serve our patients and society best. We should favor the most informative, least invasive, and less expensive technology among the multitude of available cross-sectional imaging modalities and minimize radiation when possible.

In this regard, the American Institute of Ultrasound in Medicine ( AIUM.org ) launched an initiative in 2012 “Ultrasound First,” which advocates the use of ultrasound examinations before other imaging modalities when the evidence shows that ultrasound imaging is at least equally, if not more, effective for the target anatomic area. This tenet applies particularly to obstetric and gynecologic patients for whom a skillfully performed and well-interpreted ultrasound image usually obviates the need to proceed to additional more costly and complex cross-sectional imaging techniques.

Yet still today, many women with pelvic pain, masses, or flank pain first undergo computed tomography (CT) scans and those with Müllerian duct anomalies typically have magnetic resonance images (MRIs). Not uncommonly, CT or MRI of the pelvis often yield indeterminate and confusing findings that then require clarification by ultrasound imaging. The use of CT scans has tripled since 1993, and CT scans done in 2007 could result in as many as 29,000 future cancers in the United States, with the largest contribution to this risk arising from the CT of the pelvis and abdomen. For example, patients with suspected kidney stones frequently have a CT scan first, despite the associated radiation burden. A recent study compared initial evaluation of patients with nephrolithiasis by ultrasound imaging or by CT. This analysis showed no significant differences in subsequent complications, pain scores, return emergency visits, or hospitalizations. In addition, most of the patients who were evaluated first by ultrasound imaging ultimately did not need a CT scan, sparing radiation exposure.

This clinical opinion presents the current capabilities of ultrasound imaging as the first-line imaging technique for the nonpregnant female pelvis for most clinical scenarios. Ultrasound imaging has evolved very rapidly from the early days of “black dots on a white screen” to the current very sophisticated and high-resolution displays that use both 2-dimensional (2D) and 3-dimensional (3D) technology and blood flow mapping. The advent of the high-resolution endocavitary probes and the use of color Doppler imaging for blood flow mapping have further enhanced the diagnostic capabilities of this imaging modality. Several key technical advances have rendered ultrasound imaging an effective first-line (and often only) imaging modality for most gynecologic patients: (1) volume (3D/4-dimensional) imaging, (2) real-time transvaginal ultrasound imaging with sonographically enhanced physical examination, and (3) Doppler techniques for blood flow evaluation.

3D ultrasound imaging

Currently available 3D/4-dimensional volume ultrasound imaging can produce images of the female pelvis of comparable quality and orientation to those of MRI and CT but without radiation and at relatively lower cost. Years ago, ultrasound examinations required filling a woman’s bladder and obtaining a series of 2D images one at a time, which rendered this approach very operator-dependent and limited to certain views that did not require reconstruction. Today, 3D volume ultrasound imaging allows the automated acquisition of an entire volume that, in turn, can generate hundreds of images and be used to reconstruct any view in any orientation. Furthermore, 3D ultrasound imaging is less expensive and less time-consuming than MRI. Bowel peristalsis does not affect ultrasound imaging as it does MRI, and many patients find this modality more comfortable than MRI. In contrast to MRI, patients with metal prostheses and pacemakers can undergo 3D ultrasound imaging that will yield similar images. Since the advent of volume imaging in ultrasound imaging, reconstructed views of the pelvis (such as the coronal view of the uterus) have greatly improved our ability to use ultrasound imaging to answer the vast majority of clinical questions in gynecology.

Three-dimensional volume sonography has now become an essential new tool in the ultrasound armamentarium that has proved just as effective as MRI for the demonstration of Müllerian duct anomalies, which include cervical duplications ( Figure 1 ). Three-dimensional ultrasound imaging, like MRI, can produce an image of the uterine contour and the entire endometrial cavity simultaneously. Furthermore, 3D ultrasound imaging provides the ability to manipulate the volumes in any orientation for complete evaluation of the uterus, regardless of its orientation or rotation. Multiple studies have compared 3D ultrasound imaging with other imaging modalities and with operative findings, hence establishing the equivalency of 3D ultrasound imaging to MRI in diagnostic accuracy of Müllerian anomalies. Indeed, the accuracy of both 3D ultrasound imaging and MRI for the diagnosis of the specific type and extent of uterine malformations typically exceeds 90-95%. Three-dimensional ultrasound imaging has emerged as the ideal imaging modality not only when examining patients with infertility but also for examining patients with pelvic pain associated with embedded intrauterine devices, fibroid tumors, adenomyosis, adnexal masses, torsion, endometriosis ( Figures 2-5 ). Ultrasound volume imaging makes it possible to localize fibroid tumors, polyps, and hydrosalpinges with high precision, as well as other uterine abnormalities ( Figures 3-6 ). We must educate the medical community to consider adopting 3D ultrasound imaging as the first assessment tool for specific gynecologic indications, such as the evaluation of the uterus for Müllerian anomalies or localization of intrauterine devices or other intracavitary lesions. In this setting, it is likely that fewer women would require a costly workup that involves multiple advanced imaging studies if 3D ultrasound images were performed first.