THE ULTRASOUND APPEARANCES OF NEONATAL RENAL-VEIN THROMBOSIS

Renal vein thrombosis (RVT) is the most frequently occurring vascular condition in the new-born kidney. The predisposing factors include deh ydration, sepsis, birth asphyxia, maternal diabetes, polycythaemia and the presence of an indwelling umbilical venous catheter. (RVT) may pr esent clinically with a flank mass, haematuria, hypertension or renal failure. Many imaging modalities have been employed, but ultrasound is the technique most commonly used in the evaluation of neonates with s uspected RVT. Thrombosis commences in the small renal veins and subseq uently propagates via larger interlobar veins to the main renal vein a nd inferior vena cava (IVC). The ultrasound appearances depend upon th e stage at which the examination is performed and extent of the thromb us. Initially, the interlobular and interlobar thrombus appears as hig hly echogenic streaks. These streaks commence in a peripheral, focal s egment of the involved kidney and only persist for a few days, In the first week the affected kidney swells and becomes echogenic with promi nent echopoor medullary pyramids. Later, the swelling increases and th e kidney becomes heterogenous with loss of corticomedullary differenti ation. Grey scale ultrasound readily demonstrates thrombus within the renal vein and IVC. Adrenal haemorrhage is a recognized association an d may be identified ultrasonically. Colour Doppler scanning provides a dditional information. In the early stages of RVT, colour Doppler may demonstrate absent intrarenal and renal venous flow. Ultimately, the k idney may recover, show focal scarring or become atrophic. Thus, ultra sound provides an accessible and reliable tool in the assessment of su spected neonatal RVT.