Refractory shadowing from pelvic masses on sonography: a useful diagnostic sign for uterine leiomyomas

Our objective was to determine the diagnostic usefulness of sonography for revealing a recurrent acoustic shadowing pattern when imaging for possible uterine leiomyoma.

During an 18-month period, all pelvic masses discovered on sonography were prospectively examined for recurrent refractory shadows. Sonograms of 222 masses with a definitive final diagnosis were reviewed by two radiologists unaware of the follow-up results. Each mass was analyzed for the presence of three or more recurrent refractory shadows, each of which did not arise from an echogenic lead point. After all masses were rated independently, a consensus rating was reached for any discrepancy between observers.

Of the 222 masses, 152 (68%) were leiomyomas. The remainder resulted from a wide variety of other uterine and adnexal disorders. Agreement between the two observers regarding refractory shadows was excellent. Kappa coefficients were 0.86 at transabdominal and 0.96 at transvaginal approaches. Sensitivity of the refractory shadow pattern for leiomyomas was higher for transvaginal (87%) than for transabdominal (52%) sonography. Specificity of the refractory shadow pattern was 89% for transvaginal and 92% for transabdominal sonography. Using logistic regression analysis, we found a statistically significant association between a refractory shadowing pattern and leiomyoma for both transabdominal and transvaginal sonography (p < 0.001).

Recurrent refractory shadowing in a pelvic mass on sonography is highly suggestive of leiomyoma and can be a useful diagnostic clue for distinguishing leiomyomas from other pelvic masses.