Ultrasound Evaluation of the Ovaries

Normal and Inconsequential Findings

Although normal ovarian findings and ultrasound technique is more thoroughly discussed in Chapter 26 , a few observations unique to the ovary bear additional mention here ( Fig. 30-1 ). Ovarian follicles typically achieve a size of 2 to 3 cm before ovulation. Hence, simple (unilocular, thin-walled, anechoic) ovarian cysts less than 3 cm in greatest diameter in premenopausal women should generally be considered normal findings. In order to prevent confusion with pathologic findings, it is best not to use the term “cyst” for normal ovarian structures and better to describe them as follicles or to simply report the ovary as normal. Simple ovarian cysts less than 1 cm in greatest diameter may be present in postmenopausal women and have been reported in approximately 20% of women 5 or more years following menopause. Hence, simple ovarian cysts less than 1 cm in maximal diameter in a postmenopausal woman generally require no follow-up and are considered inconsequential. The corpus luteum, which typically appears as a thick-walled cystic lesion less than 3 cm in diameter with internal echoes and crenulated wall, should also be recognized as a normal finding in premenopausal women. The wall of the corpus luteum may be quite vascular on Doppler interrogation.

Echogenic foci are a normal finding in many ovaries ( Fig. 30-2 ). Tiny echogenic foci, measuring 1 to 3 mm in width, have no posterior shadowing (although comet-tail artifact may be seen) and may be due to psammomatous calcifications associated with epithelial inclusion cysts, hemosiderin deposition, or bright specular reflections off the back walls of tiny follicles. These ovarian echogenic foci are found both in premenopausal and postmenopausal women. They are generally of no significance and may occasionally be helpful in identifying an ovary. Larger echogenic foci in the ovary, usually from isolated calcifications, are also typically benign findings ( Fig. 30-3 ). Echogenic foci 5 mm and larger, some of which may demonstrate posterior acoustic shadowing, seen in otherwise normal ovaries have been attributed to corpus albicans. Some association between these foci and adenofibromas has been reported. The pattern of calcifications within the ovary should be examined, as a more extensive peripheral rind of calcifications has been reported in a patient with endosalpingiosis and serous borderline ovarian neoplasms. Larger coarse ovarian calcifications, in the absence of a mass, are generally benign and can be followed sonographically. Anecdotal evidence suggests that patients with larger or more extensive calcifications in an otherwise normal-appearing ovary should receive additional evaluation or closer follow-up.

Ovarian Cysts with Typical Benign Features

Ovarian lesions with classic features of simple cysts, hemorrhagic cysts, endometriomas, or dermoids are highly likely to be benign. It is important to recognize the characteristic sonographic features that, when seen, are highly predictive of these benign entities. Reliable characterization of ovarian masses using these sonographic features requires that the mass be fully and adequately visualized by ultrasound. Occasionally, in a patient with a suboptimal ultrasound examination, the interpreting physician will need to decide how to proceed based on available imaging findings and degree of clinical concern. When reporting on adnexal masses seen on pelvic sonograms, it is important to describe specific sonographic features (detailed later) that allow one to determine the likely diagnosis. Use of the word “complex” as a descriptor, with no additional explanation, is problematic as the “catch-all” term is often used for any cystic mass that is not a simple cyst. There are many features that may result in a “complex” sonographic appearance, including a typical reticular pattern suggesting benign hemorrhagic cyst and typical solid nodule worrisome for malignant ovarian carcinoma. Thus, if an ovarian cyst is reported as “complex,” further descriptors detailing those features making it complex should also be provided.

Simple Cysts

As with cysts elsewhere in the body, ovarian cysts with thin walls, anechoic internal contents, posterior acoustic enhancement, and no septations or solid components meet sonographic criteria for simple cysts ( Fig. 30-4 ). Follicular or corpus luteal cysts and serous cystadenomas may appear as simple cysts by sonographic criteria. Simple ovarian cysts occur in 4% to 17% of postmenopausal women and the majority resolve or remain stable on follow-up ultrasound evaluation. However, annual follow-up sonography for simple ovarian cysts larger than 1 cm (though some practices may choose to raise this threshold to 3 cm) is recommended in postmenopausal women. In premenopausal women, it is recommended that cysts between 5 and 7 cm in largest diameter be followed yearly by ultrasound examination. The vast majority of simple ovarian cysts are benign. With increasing cyst size, however, there is a risk of inadequate assessment of the cyst wall for detection of small solid nodules or papillary formations, which, if present, increase the likelihood of malignancy. The rare occurrence of malignancy in an apparent simple ovarian cyst is more likely in larger cysts, in which small mural nodules may be overlooked. Hence, when evaluating what appears to be a simple cyst, it is important to confirm that the cyst is adequately imaged in its entirety and to carefully assess for small nodules before concluding that it is indeed a simple cyst. Simple cysts measuring larger than 7 cm are still likely benign, though one should consider further imaging evaluation with MRI to confirm that there is no solid component overlooked by sonography.