Neonatal renal vein thrombosis: grey-scale and Doppler ultrasonic features

Renal vein thrombosis RVT is the most common non-catheter related venous thromboembolic events VTE in newborns and is responsible for approximately 10% of all VTE in newborns. Almost 80% of all RVT present within the first month and usually within the first week of life. Currently ultrasound is the radiographic test of choice because of its practicality, sensitivity and lack of adverse effects. The sonographic features vary according to the severity, the extent of the thrombus, the development of collateral circulation and the stage of renal vein thrombosis. Initial diagnostic features include, renal enlargement, echogenic medullary streaks that have a vascular or perivascular distribution, thrombus in the vein prominent echopoor medullary pyramids, subsequently loss of corticomedullary differentiation, reduced echogenicity around the affected pyramids and echogenic band at the extreme apex of the pyramid. Higher resistance index and absent, steady, or less pulsatile venous flow on the affected side compared with flow in the contralateral kidney are helpful Doppler signs. While sonography may be useful in revealing the venous and renal morphology, it is insufficiently reliable for assessment of the functional impact of these morphologic findings. There are no characteristic grey-scale or Doppler ultrasound prognostic features to predict outcome of neonatal RVT and long-term follow up of those children is required.