A uterine ultrasound is a non-invasive imaging method using high-frequency sound waves to create real-time pictures of the reproductive organs within the pelvis. This technique routinely evaluates the size, shape, and condition of the uterus, endometrium, and ovaries. Understanding the basic language of these images and the corresponding report can help a patient better comprehend the findings and discuss them with a healthcare provider.
Understanding the Ultrasound Image Basics
The ultrasound image is a grayscale picture, where the appearance of different tissues is represented by varying shades of black, white, and gray, based on how much of the sound wave is reflected back to the probe. Structures that are fluid-filled, such as a simple cyst or urine in the bladder, do not reflect sound waves and therefore appear black; this is termed anechoic.
Dense tissues, like scar tissue or the fibrous components of some masses, reflect nearly all the sound waves and appear bright white, a feature known as hyperechoic. Most soft tissues, including the muscular wall of the uterus, appear in various shades of gray, termed isoechoic or hypoechoic. The report uses these terms to describe the internal texture of organs.
The images are typically displayed in two main orientations: sagittal (longitudinal) and transverse (cross-sectional). The sagittal view shows the uterus from top to bottom, allowing for measurement of its length, while the transverse view shows a horizontal slice, which is used to measure width. Labels on the screen, often marked with letters like “TR” or “LG,” indicate the imaging plane, providing a spatial reference for the structures being viewed.
Identifying Normal Uterine Structures
The uterus is a pear-shaped organ whose walls are composed of the myometrium, the muscular layer. On a normal ultrasound, the myometrium appears relatively uniform and mid-gray, described in reports as having a homogeneous echotexture. The myometrium can be further divided into three layers, with the innermost layer, called the junctional zone, sometimes appearing slightly darker than the middle and outer layers.
The cervix, the lower, cylindrical portion of the uterus, also has a generally homogeneous, mid-gray appearance. The most dynamic part is the endometrium, the lining of the uterine cavity, which is seen as a central stripe of tissue. This lining undergoes dramatic changes that correspond directly to the phases of the menstrual cycle.
During the proliferative phase, after menstruation, the endometrium begins to thicken and often displays a characteristic trilaminar or “triple stripe” appearance. This pattern consists of a bright outer layer, a darker middle layer, and a bright central line where the front and back of the endometrium meet. Following ovulation, in the secretory phase, the lining becomes uniformly thick and bright white (hyperechoic), losing the triple-stripe pattern due to increased fluid and tissue content.
Key Measurements and Terminology
The ultrasound report provides specific measurements that quantify the size and condition of the uterus and its lining. Uterine size is standardized by measuring its length (fundus to cervix), anteroposterior depth, and transverse width. The typical adult uterus, in a woman of reproductive age, measures approximately 6 to 9 centimeters in length.
The most reported measurement is Endometrial Thickness (ET), which is taken in the sagittal view at the thickest point of the central stripe, measuring both layers together. The thickness is highly dependent on the patient’s menstrual cycle phase. For example, in a premenopausal woman, the ET can range from 2 to 4 millimeters during menstruation, increase to a maximum of about 11 millimeters in the late proliferative phase, and reach up to 16 millimeters during the secretory phase.
For postmenopausal women who are not on hormone therapy, an ET greater than 5 millimeters is considered an important finding, as it is a common threshold used to determine if further testing, such as a biopsy, is needed. Beyond size, the report also uses terminology to describe the tissue quality, such as homogeneous (uniform texture), which is normal, or heterogeneous (mixed texture), which may suggest the presence of a mass or other pathology. The uterine position, such as anteverted (forward-tilting) or retroverted (backward-tilting), is also noted, though this is usually a normal variation.
Interpreting Common Abnormal Findings
Abnormal findings in a uterine ultrasound often relate to masses within the myometrium or the endometrium. Uterine fibroids, also called leiomyomas, are common benign tumors that originate in the muscular wall. On an ultrasound, fibroids typically appear as well-defined, solid masses that are usually darker than the surrounding myometrium, described as hypoechoic. They may also cause an acoustic shadow, appearing as a dark area behind the mass, which is a common visual marker of a dense lesion.
Endometrial polyps are benign growths of the endometrial lining that project into the uterine cavity. These appear as bright, well-defined masses that are echogenic and homogeneous, often surrounded by the endometrial fluid. A key feature that can help distinguish a polyp is the presence of a single blood vessel, or feeding vessel, supplying the mass, which can be visualized with Doppler ultrasound.
The report may also comment on ovarian cysts, which are frequently seen and are often simple, fluid-filled structures that appear entirely black. These simple cysts are generally benign and are a reflection of normal ovarian function. Findings like these are usually described by their size and location, providing the essential details for a healthcare provider to determine the next steps in care.