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Renal cystic disease may be caused by both inherited and noninherited causes. The differential diagnosis may be narrowed based on the presence of nephromegaly, discrete cysts versus numerous microcysts, and the identification of multiorgan involvement. Renal neoplasms may be detected on renal ultrasound, which is particularly good at demonstrating renal vein involvement. Although CT and MR imaging are often used to characterize lesions, contrast-enhanced ultrasound is emerging as an alternative imaging modality. Spectral Doppler ultrasound is useful in the setting of suspected renovascular hypertension, with direct signs including visualization of the stenosis, increased peak systolic velocity greater than 200 cm/s, and increased renal-to-aorta peak systolic velocity greater than 3.5. Indirect signs include tardus parvus waveform distal to the stenosis.