Ultrasound images Renal vein thrombosis

This can occur when chronic renal disease is already present or in cases of a coagulation disor-der with increased tendency to thrombose, for example polycythaemia. It is frequently associated with nephrotic syndrome. Other associated factors include the oral contraceptive pill and the use of steroids. Tumour thrombus from RCC is also prone to invade the ipsilateral renal vein, and sometimes may extend into the IVC and even renal artery. Thrombus in the renal vein, whether secondary to a malignancy or thrombocythaemia can travel up the IVC forming a source of emboli. If nonmalignant, the thrombus may be successfully treated medically and the renal function can be preserved even if the vein is totally occluded.

Ultrasound images of renal vein thrombosis It is often possible to see echo-poor thrombus within a dilated renal vein, running beside the renal artery in an axial section through the renal hilum. Colour Doppler confirms absent venous flow. Perfusion within the kidney itself is reduced and there may be a highly pulsatile arterial waveform with reversed diastolic flow (Fig. ultrasound images below),

Renal vein thrombosis. Small shrunken kidney (6 cm) demonstrating hardly any perfusion, apart from a tiny interlobar artery with forward and reverse flow. although this is not commonly seen in the native kidney. If the throm bus produces a total and sudden occlusion, the kidney becomes oedematous and swollen within the first 24 h. Eventually it will shrink and become hyperechoic. Partially occluding thrombus is more difficult to diagnose as the changes in the kidney may not be apparent. However, a non-dilated renal vein with good colour Doppler displayed throughout has a high negative predictive value. Incomplete thrombosis may still demonstrate venous flow within the kidney, although the arterial waveforms are of lower velocity than normal, with a marked reduction in the systolic peak. Forward diastolic flow may be preserved at this stage.
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