Objective: The objective of our study was to describe the "waist" sign as a feature of hydrosalpinx and to calculate the likelihood ratio of sonographic findings for predicting that a cystic adnexal mass is a hydrosalpinx.
Materials and methods: Consecutive institutional records were reviewed to identify patients with surgically excised cystic adnexal masses and preoperative sonograms that had been used to identify the mass. Two radiologists blinded to outcome reviewed the sonograms and recorded the presence of five specific sonographic findings: incomplete septation, short linear projection, small round projection, tubular shape, and presence of a waist. The likelihood ratios of these signs and combinations of signs for the diagnosis of hydrosalpinx were calculated.
Results: There were 55 patients with 67 cystic adnexal masses. Of the 67 cystic adnexal masses, there were 26 hydrosalpinges (39%), 36 cystic ovarian neoplasms (54%), and five paraovarian masses (7%). The likelihood ratios for the sonographic findings were as follows: incomplete septation, 2.1; short linear projection, 3.5; small round projection, 2.7; tubular shape, 10.5; and waist sign, 20.5. The waist sign in combination with tubular shape was found in 12 hydrosalpinges and no other masses (likelihood ratio of between 18.9 and infinity). Small round projection combined with tubular shape was found in 14 hydrosalpinges and one other mass (likelihood ratio of 22.1).
Conclusion: Hydrosalpinx can be diagnosed with the highest likelihood when a tubular mass with the waist sign or a tubular mass with small round projections is encountered. Incomplete septations and short linear projections are less discriminating findings of hydrosalpinx.