Objective To evaluate color Doppler ultrasonography （CDU） appearances of renal vein thrombosis （RVT） and its diagnostic value.Methods Ten patients with RVT were analyzed retrospectively. Renal structure

distributions of intrarenal flow signals

echogenicity

and flow fullness in main renal veins were observed with CDU. Resistance index （RI） was recorded from the waveforms of segmental or interlobar renal artery.Results Ten kidneys in nine patients were confirmed to have thrombus within the main renal veins

and one patient was confirmed to have thrombus within the small intrarenal veins. The appearances of the main renal vein thrombosis included full of solid echogenicity or strip echogenicity and complete or partial filling defect within the main renal veins

and absent or a few intrarenal venous flow signals in 70% of kidneys involved. The appearances of intrarenal vein thrombosis included obscure renal structure and no venous flow signal within the involved part of the kidneys. Reverse diastolic flow in the intrarenal artery had only a sensitivity of 36% （4/11）; in other 7 kidneys without intrarenal arterial reverse diastolic flow

increased RI （mean

0.84; range

0.74-0.96） was found.Conclusion CDU is helpful for rapid clinical diagnosis and follow-up of RVT

and therefore can be the first imaging modality of choice for RVT.