Purpose: We investigated the role of power Doppler US with a high-frequency and high-resolution transducer (13 MHz) in the visualization of interlobular arterioles in patients with normally functioning renal transplants or with chronic rejection.
Material and methods: We examined 15 patients (mean age 15 years; range 10-18 years) with a General Electric 500 MD unit using 7.5 and 13 MHz linear transducers. In all the patients serum creatinine and diuresis were evaluated; 4 patients underwent US-guided biopsy that resulted in the diagnosis of chronic rejection.
Results: Normally functioning renal transplants were found in 11 patients and chronic rejection was seen in 4. In normally functioning renal transplants, interlobular vessels could be depicted as "cortical blush" with the 7.5 MHz transducer; in the same patients power Doppler US with the 13 MHz transducer permitted a correct evaluation of interlobular vessels that were arranged in series like a palisade. In chronic rejection power Doppler US with the 13 MHz transducer better depicted cortical vascularity and showed irregular, narrow arteries.
Conclusion: Power Doppler US with a 13 MHz transducer is particularly useful in children after renal transplants due to their reduced tissutal thickness. The lateral resolution of 13 MHz transducers (< 0.3 mm) allows to separate interlobular vessels from each other and the high frequency of the probe can depict interlobular vessels in the peripheral cortex. The optimal visualization of cortical vascularity with a 13 MHz transducer allows early detection of chronic rejection.