O-RADS and IOTA Simple Rules: Stratification of Adnexal Masses and Protocol Template
According to the updated IOTA Group consensus (2026), for characterizing ovarian masses on ultrasound, the IOTA Steering Committee recommends using IOTA benign descriptors, the ADNEX model (Assessment of Different NEoplasias in the adneXa), and a two-step strategy. These approaches allow assigning a category in the Ovarian-Adnexal Reporting and Data System (O-RADS), as defined by the American College of Radiology (ACR), and using it for appropriate management decisions.
O-RADS Categories in Conjunction with IOTA
Normal ovaries or functional findings are classified as O-RADS 1. Masses to which an IOTA benign descriptor applies are classified as O-RADS 2. Further stratification of O-RADS categories in the provided fragments is not detailed [clarify].
| O-RADS Category | Correspondence with IOTA |
|---|---|
| O-RADS 1 | Normal ovaries or functional findings |
| O-RADS 2 | Masses to which an IOTA benign descriptor applies |
IOTA Simple Rules
The most well-known IOTA framework is the Simple Rules approach, which classifies masses based on the presence of benign features, malignant features, both, or neither (Holland, 2026). The strength of the system lies in its practicality. The diagnostic performance of IOTA Simple Rules has been confirmed in a meta-analysis (Nunes et al., 2014) and external validation studies, including work by non-expert researchers (Tinnangwattana et al., 2015) and comparisons of centers with varying prevalence of ovarian cancer (Ruiz de Gauna et al.). Specific criteria for B- and M-features in the provided fragments are not included [clarify].
Structured Description Before Model Application
A mass should be described using structured morphology before applying any model (Holland, 2026). This makes the report clearer even when the clinician does not formally use an assessment system and allows expert reviewers, multidisciplinary teams, and surgeons to understand why the researcher assessed the mass as having low or high risk. A well-structured report can often be re-triaged based on the description alone.
External Validation
The diagnostic effectiveness of IOTA simple descriptors and simple rules has been confirmed in multicenter prospective external validation studies (Sayasneh et al., 2013; Alcazar et al., 2016). The ADNEX model has also undergone multicenter external validation for assessing the risk of ovarian cancer preoperatively (Sayasneh et al., 2016).
Frequently asked questions
What IOTA approaches are recommended for characterizing ovarian masses?
The IOTA Steering Committee recommends IOTA benign descriptors, the ADNEX model, and a two-step strategy; they allow assigning an O-RADS category (ACR).
How do O-RADS categories 1 and 2 relate to findings?
O-RADS 1 refers to normal ovaries or functional findings; O-RADS 2 refers to masses to which an IOTA benign descriptor applies.
What is the basis of the IOTA Simple Rules classification?
It is based on the presence of benign features, malignant features, both simultaneously, or neither.
Is a structured description necessary if the model is not formally used?
Yes. Morphology is described in a structured manner before applying any model; this allows re-triaging the mass based on the description alone.
Has the effectiveness of Simple Rules been confirmed among non-experts?
Yes, in the study by Tinnangwattana et al. (2015), the differentiation of benign and malignant masses by non-expert researchers was evaluated.