Small (≤3-cm) renal masses: Detection with CT versus US and pathologic correlation

PURPOSE: To determine the sensitivities of computed tomography (CT) and ultrasound (US) for detection and characterization of surgically verified small renal lesions. MATERIALS AND METHODS: Twenty-one patients with von Hippel-Lindau disease or hereditary papillary renal cancer underwent CT and US before partial nephrectomy or enucleation; 205 renal masses were removed (92% were <3 cm). Detection rates and accuracy of CT and US in the characterization of renal morphology were correlated with lesion size. RESULTS: CT and US detection rates for lesions of 0-5 mm were respectively 47% and 0%; 5-10 mm, 60% and 21%; 10-15 mm, 75% and 28%; 15-20 mm, 100% and 58%; 20-25 mm, 100% and 79%; and 25-30 mm, 100% and 100%. Among the lesions 10-35 mm, 80% and 82% were correctly characterized with CT and US, respectively. CONCLUSION: A substantial proportion of lesions under 1 cm were not detected with either modality. Neither CT nor US was superior in the characterization of lesions 3 cm or less. CT and particularly US screening studies in patients with von Hippel-Lindau disease should be interpreted cautiously because missed or mischaracterized small renal lesions are a frequent problem in these patients.