Long-Term Prognostic Impact of Contrast-Enhanced Ultrasound and Power Doppler in Renal Transplantation.

BACKGROUND: Contrast-enhanced ultrasound (CEUS) and power Doppler ultrasound (US) are established tools in the study of acute renal allograft (RA) dysfunction. The aim of this study was to investigate their long-term prognostic impact. MATERIALS AND METHODS: A total of 39 kidney recipients underwent CEUS and US at 5 and 15 days and at 1, 3, 6, and 12 months after grafting, with yearly clinical, laboratory, and US follow-up for a total of 4 years. CEUS analysis according to the gamma variate model was performed on cortical and medullary regions. Patients were divided into 2 subsets: death or graft failure vs patients with functioning grafts; higher vs lower than 50% glomerular filtration rate (GFR) reduction from the first month to the fourth year after grafting. Receiver-operator characteristic (ROC) analysis for death/graft failure and 50% GFR reduction events was performed for variables with significant differences between groups (t test) or with significant correlation to GFR (Pearson correlation). RESULTS: ROC analysis confirms the reliability of clinical and radiologic variables for the evaluation of long-term graft survival or of GFR reduction, with high sensitivity (for resistive index) or specificity (for GFR, medullary peak, and regional blood flow). CONCLUSIONS: Combining CEUS and US allows the evaluation of long-term RA function in terms of GFR reduction and graft survival. Resisitive-indexes show a good sensitivity, relating to kidney disfunction, while CEUS parameters show a good specificity, identifiying well-perfused grafts.

Contrast-enhanced sonography in early kidney graft dysfunction.

OBJECTIVES: The aim of this study was a comparison of contrast-enhanced sonography (CEUS) and power Doppler ultrasound (US) findings in renal grafts within 30 days posttransplantation. METHODS: A total of 39 kidney recipients underwent CEUS (SonoVue bolus injection) and US examinations at 5 (T0), 15 (T1), and 30 (T2) days after grafting. The results were correlated with clinical findings and functional evolution. Fourteen patients displayed early acute kidney dysfunction: 10 had acute tubular necrosis (acute tubular necrosis [ATN] group); four acute rejection episodes (ARE group); 25 with normal evolution (as control, C group). Renal biopsies were performed to obtain a diagnosis in the four ATN cases and in all ARE patients. Creatinine and estimated glomerular filtration rate were used as kidney function parameters. CEUS analysis was performed both on cortical and medullary regions while US resistivity indexes (RI) were obtained on main, infrarenal, and arcuate arteries. From an analysis of CEUS time-intensity curves, we computed peak enhancement (PEAK), time to peak (TTP), mean transit time (MTT), regional blood flow (RBF) and volume (RBV), and cortical to medullary ratio of these indies (RATIO). RESULTS: An increased RI was present in the ATN and ARE groups as well as a reduced PEAK and RBF. RATIO-RBV and RATIO-MTT were lower than C among ATN cases, while TTP was higher compared to C in ARE. No statistical difference was evidence for RI between ATN and ARE groups. MTT (T0) was significantly related to creatinine at follow-up (T2). CONCLUSIONS: US and CEUS identified grafts with early dysfunction, but only some CEUS-derived parameters distinguished ATN from ARE, adding prognostic information.