A prospective blinded study of 201 patients was performed to determine the relative sensitivities and specificities of excretory urography/linear tomography (EU/LT) and ultrasound (US) for the diagnosis of renal parenchymal masses. Computed tomography (CT) was used as a standard. EU/LT permitted detection of 10% of CT-confirmed masses (cystic or solid) less than 1 cm, 21% of lesions greater than or equal to 1 cm but less than 2 cm, 52% of lesions greater than or equal to 2 cm but less than 3 cm, and 85% of lesions 3 cm or more in diameter. US permitted detection of 26% of CT-confirmed lesions less than 1 cm, 60% of lesions greater than or equal to 1 cm but less than 2 cm, 82% of lesions greater than or equal to 2 cm but less than 3 cm, and 85% of lesions 3 cm or more in size. The results confirm the relative insensitivity of EU/LT for masses less than 3 cm in diameter and of US for masses less than 2 cm. Further, they suggest that CT may have a role not only in evaluation of cases in which the urographic or sonographic results are questionable or positive, but also in confirmation of apparently negative urographic findings when clinical suspicion of a lesion is high.

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A case of a cystic partially differentiated nephroblastoma treated with combined chemotherapy after removal in a 2-month old newborn is reported. Cystic partially differentiated nephroblastoma is a newly described clinicopathologic entity, involving elements of a nephroblastoma and cystic disease, and it is believed to be a pathologic derivative of the metanephric blastema and not related to renal dysplasia. Cystic partially differentiated nephroblastoma is distinguished from multilocular cysts of the kidney by the presence of partially differentiated renal elements in the septa of cysts. The aggressive appearance of the cells led to the treatment of this tumor as potentially malignant.