[Ultrasonography for the study of small renal masses].

Objectives: To perform an update on the usefulness of ultrasound in the study of small size renal tumors and its current possibilities.

Methods: We review the results of ultrasound in this pathology with the addition of the most recent technological advances such as a harmonic digital converters and power color Doppler. We analyze its contribution to the differential diagnosis of the cystic pathology, to the definition of solid masses, to the detection and characterization of small size masses, and to the definition of the vascular patterns of various tumors.

Results: Ultrasonography offers a diagnostic safety of 98% in cystic masses, being able to detect them from 0.5 cm diameter in favourable conditions. The differential diagnosis of multiloculated masses, multivesicular hydatid cyst, multiloculated cystic nephroma, and multiloculated cystic carcinoma still poses great difficulty, the same way it happens with other radiological tests. For solid masses, the greater image resolution has lead to a progressive increase in the incidental detection of tumors and the percentage of patients candidates to conservative surgery due to the decrease in size. It is easy to differentiate between adenocarcinoma and angiomyolipoma, up to 85% of the cases, but the rest of the tumors do not have specific characteristics. For small size masses, smaller than 3 cm, ultrasound sensitivity is clearly inferior to CT scan. Power color Doppler helps to confirm the existence of solid masses and helps a better differential diagnosis with pseudo tumors.

Conclusions: The modern ultrasound techniques provide a high cost-effectiveness both in detection and definition of the nature of small size renal masses.