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CEUS Bosniak Classification of Indeterminate Renal Cysts: Single-Institution Experience
Louis Mazzarelli, MD, Joseph Renzulli, MD, Joseph Brito, MD, Timothy Tran, MD.
Lawrence and Memorial and Westerly Hospitals, Yale New Haven Health, New London, CT, USA.
BACKGROUND: Contrast-enhanced ultrasound (CEUS) has emerged as a radiation-free modality for characterizing indeterminate renal cysts using the Bosniak classification system. While CT and MRI remain standard of care, CEUS offers real-time vascular assessment without ionizing radiation or nephrotoxic contrast. We report a single-institution experience applying the 2019 Bosniak v2 classification to renal cysts evaluated by CEUS.
METHODS: Patients with indeterminate renal cystic lesions who underwent CEUS evaluation were retrospectively identified from a single institution. All studies were performed and interpreted by a radiologist with 5 years of dedicated CEUS experience. Lesions were classified using the 2019 Bosniak v2 criteria. Reference standards included surgical pathology, percutaneous biopsy, and imaging follow-up. CEUS Bosniak classification was compared to contemporaneous CT or MRI when available.
RESULTS: Forty lesions in 37 patients were evaluated. CEUS Bosniak classification yielded: Class I (n=11, 27.5%), Class II (n=22, 55%), and Class IV (n=7, 17.5%). No Class IIF or III lesions were identified. All 7 Class IV lesions underwent surgical resection and were confirmed malignant on pathology: clear cell RCC (n=4), clear cell papillary RCC (n=1), multilocular cystic neoplasm of low malignant potential (n=1), and papillary cell neoplasm (n=1). All Class I and II lesions were benign on imaging surveillance (median follow-up 7 months, range 1-36). CEUS achieved a sensitivity of 100% and specificity of 100% for malignancy using Class IV as the threshold. CEUS classification was concordant with CT/MRI Bosniak class in 31/40 lesions (77.5%); all discordances were single-class differences between Class I and II, without clinically consequential up- or down-staging.
CONCLUSIONS: CEUS Bosniak classification demonstrates excellent malignancy prediction for Class IV lesions, with 100% PPV in this cohort. Agreement with CT/MRI was high, with all discordances confined to low-grade classes without clinical consequence. CEUS represents a viable, radiation-free alternative for renal cyst surveillance in appropriately selected patients
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