What is the initial approach for evaluating an adnexal mass, considering tools like ADNEX (Adnexal Disease National Emergency X-ray) and IOTA (International Ovarian Tumor Analysis)?

Initial Approach for Evaluating Adnexal Masses Using ADNEX and IOTA Tools

Transvaginal ultrasound combined with transabdominal ultrasound is the most appropriate initial imaging modality for evaluating adnexal masses, with standardized risk assessment tools like IOTA simple rules and ADNEX model recommended for characterization and risk stratification. 1

Primary Imaging Approach

• Transvaginal ultrasound is the most useful initial imaging modality with sensitivity >90%, with diagnostic performance improved when performed by experienced operators 1
• Combined transvaginal and transabdominal technique is recommended to allow for comprehensive evaluation, with the transvaginal component providing detailed assessment and transabdominal component helpful for larger lesions (>10 cm) 1
• Color and power Doppler evaluation should be considered an integral part of the complete ultrasound assessment to identify internal vascularity within suspected adnexal lesions 1

Standardized Risk Assessment Tools

IOTA Simple Rules

• IOTA simple rules use a binary system (no flow versus very strong flow) for color Doppler evaluation 1
• The system applies specific ultrasound parameters to differentiate benign from malignant adnexal masses 1
• IOTA simple rules are applicable in approximately 69% of adnexal masses and have high specificity but slightly lower sensitivity compared to O-RADS 2, 1

ADNEX Model

• The Assessment of Different NEoplasias in the adneXa (ADNEX) model is the first risk model that differentiates between benign and four types of malignant ovarian tumors: borderline, stage I cancer, stage II-IV cancer, and secondary metastatic cancer 3
• ADNEX model uses a combination of clinical and ultrasound features including classically benign imaging features, lesion size, locularity, size and number of solid components, and degree of vascularity 1
• When used in a two-step strategy (applying IOTA simple rules first, then ADNEX for indeterminate cases), this approach demonstrates excellent discrimination between benign and malignant masses with AUC of 0.94 4

Risk Stratification Algorithm

1. Initial Evaluation: Perform combined transvaginal and transabdominal ultrasound with color Doppler 1, 5
2. Apply IOTA Simple Rules: If applicable, use to classify as likely benign or likely malignant 1, 2
3. For Indeterminate Cases: Apply ADNEX model using a risk threshold of 10% for malignancy 2, 4
4. For High-Risk Masses: Consider referral to gynecologic oncology 6
5. For Low-Risk Masses: Consider follow-up ultrasound monitoring, as the risk of complications is very low (5-year cumulative incidence of malignancy approximately 0.4%) 4

Performance Comparison of Risk Assessment Tools

• O-RADS has demonstrated significantly higher sensitivity for malignancy than the IOTA simple rules (96.8% versus 92.1%) with no significant difference in specificity (92.8% versus 93.2%) 1
• The ADNEX model without CA125 has shown excellent discrimination with AUC of 0.95 for distinguishing benign from malignant masses 4
• The two-step strategy (IOTA simple rules followed by ADNEX) has better clinical utility than ADNEX model alone at malignancy risk thresholds <3% 4

Second-Line Imaging

• MRI with IV contrast is recommended as the best alternative when ultrasound is inconclusive or limited by factors such as large mass size (>10 cm), poor acoustic window, or unclear organ of origin 1, 5
• MRI performs superiorly to ultrasound in tissue characterization but is not the first-line modality 1
• CT is typically not useful for initial workup and characterization of adnexal masses due to suboptimal soft tissue delineation 1, 5

Common Pitfalls to Avoid

• Relying solely on transabdominal ultrasound, which may provide incomplete evaluation 5
• Using CT as first-line imaging when ultrasound or MRI would provide superior characterization 5
• Failing to use color Doppler to identify vascular flow within solid areas, which is crucial for differentiating malignancy from benign solid components like clots or debris 1
• Using serum CA125 as a standalone modality for distinguishing between benign and malignant adnexal masses 6