Reproducibility of Doppler ultrasound measurement of resistance index in renal allografts.

In recent years measurements of arterial blood flow in the renal allograft have been studied in an attempt to provide a non-invasive method of diagnosing and monitoring post-transplant renal dysfunction. Many studies have involved measurement of the resistance index (RI) of arterial blood flow. Although the reproducibility of the technique has been studied in other areas of application, no such studies have been performed on the renal allograft. In this study we attempted to evaluate the reproducibility of the measurement of the RI of the interlobar artery in the renal allograft. 18 renal allograft recipients with stable functioning grafts were studied twice by each of two experienced sonographers using a colour-coded duplex Doppler ultrasound scanner, in order to determine the intraobserver and interobserver variability in the measurement of RI of the interlobar arteries in the allograft. Variability was small and although interobserver variability exceeded intraobserver variability, both were within repeatability limits adopted by the British Standards Institution. The results suggest that measurement of the RI of the interlobar artery of renal allografts is repeatable and reproducible when performed by experienced operators.

Monitoring renal allograft rejection with duplex sonography.

Thirty-six renal allograft recipients were monitored by serial duplex Doppler ultrasound studies post-transplant and during early rejection. A separate reproducibility study demonstrated no significant inter- or intra-operator variability in measurements of resistive index of an interlobar artery (RI) (2.1% [1.5%] and 3.2% [2.3%] respectively, mean [standard error] of coefficients of variance). Twenty-one patients had rejection within 3 weeks of transplantation. These grafts showed greater overall rises in the RI, from day 2 to day 5 post-transplant, than the grafts which had no rejection. Eleven of the 21 patients required more than one course of methyl-prednisolone for persistent or recurring rejection. These grafts had higher RI on the day rejection was diagnosed (81 [7.3], median [interquartile range]) compared with the remaining 10 patients (68.6 [8.7]). The 11 grafts with persistent rejection had higher RI (p less than 0.005, Mann-Whitney U-test) on day 2 post-transplant (76 [3.9]) compared with the 10 grafts successfully treated with a single course of methyl-prednisolone (63.2 [10.9]). This study demonstrates that grafts with an RI of greater than 70 on day 2 post-transplant are likely to have rejection requiring additional treatment (sensitivity--100%, specificity--80%). These patients may be candidates for earlier or alternative anti-rejection therapy.