Doppler ultrasound in renal transplantation.

resistive and pulsatility index (RI, PI ). Both are equally Introduction as useful although the RI is probably more commonly used. An RI <0.7 is normal, >0.9 abnormal, and Colour Doppler ultrasound facilitates not only a global between there is a large grey area. A PI <1.5 is assessment of the intrarenal vasculature but can also normal, and >1.8 abnormal. The higher the RI or PI be targetted to specifically examine the main renal the more likely is a diagnosis of acute rejection. artery and vein in renal transplant recipients. The technique can be used in the early transplant period to monitor patients with delayed graft function and is also useful in confirming the diagnosis of renal vein Renal vein thrombosis thrombosis. It is also a valuable non-invasive test in the diagnosis of arteriovenous fistulae and in the diagnosis and post therapeutic monitoring of transRenal vein thrombosis is an important cause of early plant artery stenosis. graft failure. It typically occurs in patients with delayed graft function in the first week following transplantation. The diagnosis can be confirmed by Doppler Normal appearances examination and although nephrectomy is usually required early detection and intervention may occaThe waveform of the graft intrarenal vessels (comsionally salvage the graft. The ultrasonic features monly the interlobar vessels) is similar to that of the include a dilated renal vein containing thrombus, native kidney and has been described as having a ‘ski absent venous flow throughout the kidney, and reverse slope’ appearance (Figure 1) with end diastolic flow diastolic flow within the main artery and intrarenal being approximately one-third or greater of the amplivasculasture (Figure 3). A low amplitude rounded tude of the peak systolic velocity. Examination of the intra-arterial waveform has also been observed in a main transplant artery may be technically difficult due few patients with incomplete renal vein thrombosis. to vessel tortuosity however the intrarenal branches and the main renal vein itself are normally easily visualized. Renal artery stenosis