Echogenic ovarian foci without shadowing: are they caused by psammomatous calcifications?

To determine and report the spectrum of ultrasonographic appearances of echogenic ovarian foci (EOF) without shadowing in otherwise normal ovaries and the histopathologic and physical characteristics of these foci.

The appearances of foci on transvaginal pelvic sonograms obtained in 189 patients with EOF were prospectively analyzed. The foci were classified according to bilaterality, size, number (<5, 5-10, or >10), and location (peripheral, central, or diffuse). At histopathologic analysis, resected normal ovaries, seven with and 10 without echogenic foci, in a water bath were scanned. The foci were then localized for histopathologic correlation. To assess the physical properties of the foci, tissue-mimicking water- and glycerol-based phantoms, with voids of different diameters, in a water bath were scanned with 8- and 70-MHz transducers.

At appearance analysis, EOF (mean diameter, 1.8 mm +/- 0.6 [SD]) were detected unilaterally in 103 (54.5%) of 189 patients. EOF were distributed peripherally in 183 (66.5%), centrally in 15 (5.5%), and diffusely in 77 (28.0%) of 275 ovaries. There were fewer than five foci in 123 (44.7%), five to 10 foci in 91 (33.1%), and more than 10 foci in 61 (22.2%) of 275 ovaries. At histopathologic analysis of the seven ovaries with EOF, the foci had tiny cysts with no evidence of calcifications. A single cyst cluster was identified in two of 10 ovaries that did not have echogenic foci. At physical property analysis, single echogenic foci were associated with specular reflection from the walls of unresolved cysts that were comparable in size to the ultrasound wavelength (about 0.50 mm).

EOF without shadowing are caused by a specular reflection from the walls of tiny unresolved benign cysts rather than by psammomatous calcifications.