[Utility of the Doppler technique in the uro-nephrologic field]

Doppler techniques (echo Doppler, Color Doppler) may be useful in many urologic and nephrologic applications. Renal vein thrombosis can be determined by discovering a combination of a distended, thrombus-filled renal vein and the absence of detectable flow. The use of Doppler as screening technique for suspected renal artery hypertension remains controversial. Although patency of the renal artery can be assessed by Doppler, it is difficult to evaluate always the entire course of the vessel and it is impossible to detect multiple renal arteries. In the renal masses Doppler can investigate the vascularity: most malignant lesions gives rise to abnormal, high frequency, Doppler shifted signals that can aid the differential diagnosis of benign and malignant conditions. Doppler has recently been shown to help distinguish between the dilated renal pelvis and renal obstruction. A Resistive Index (RI) of 0.70 or greater is suspicious for obstruction, while a value of less than this virtually rules out the diagnosis in most cases. The use of Doppler techniques in renal transplants has become routine. Doppler assesses the presence of blood flow in the main renal arteries and veins, the presence of post-surgical abnormalities such as pseudo-aneurysms, stenoses, A-V fistulas and has proven useful in the evaluation of flow waveforms associated with variety of different abnormalities which can produce a decrease in renal function. Acute vascular rejection produces an increased resistance to flow with decreased, absent or reversed diastolic flow within the transplant kidney. Severe rejection produces abnormalities of the RI which are non-specific; severe acute tubular necrosis, infections, obstructions, peri-renal collections can also produce elevated RI.(ABSTRACT TRUNCATED AT 250 WORDS)