Antenatal and neonatal renal vein thrombosis: new ultrasonic features with high frequency transducers.

The ultrasonic appearances of two infants with renal vein thrombosis (RVT) are described. One infant presented in the neonatal period and one antenatally. Consistent with previous reports, one or both kidneys were enlarged, with a generalised increase in echogenicity and vascular or perivascular streaking compatible with interlobular and arcuate vessel occlusion. Using high frequency transducers (7. 0-10 MHz), we identified new features during the course of the disease. The apex of the renal papilla became hypo-echoic and there was a ring of reduced echogenicity around the affected pyramids 1-2 weeks after the acute phase. These features correlate with the known pathophysiological course of RVT, but have not been previously described using ultrasound. The features are illustrated and the mechanism is discussed.