Assessment of Chronic Renal Allograft Nephropathy Using Contrast-Enhanced MRI: A Pilot Study

OBJECTIVE. Renal allograft function monitoring has traditionally relied on functional markers such as creatinine level. Such markers are insensitive, and invasive ultrasound-guided protocol biopsies are used for allograft evaluation. This pilot study evaluates the association between renal perfusion measured noninvasively with contrast-enhanced MRI and the histologic severity of chronic allograft nephropathy. SUBJECTS AND METHODS. Chronic allograft nephropathy severity was estimated from protocol biopsy specimens using the chronic allograft damage index. We prospectively selected four patients considered to have severe chronic allograft nephropathy (chronic allograft damage index score > 4) and six patients considered to have stable allograft function ;(chronic allograft damage index score <= 4). Renal perfusion (milliliters per minute per gram) was estimated during passage of a gadopentetate dimeglumine bolus using an up-slope method relating the delivery of gadopentetate dimeglumine to tissue from the supplying artery. Two levels of the transplant kidney were evaluated. The association between average MRI renal perfusion of both slices and chronic allograft damage index score was studied using multiple linear regression. RESULTS. We observed a statistically significant association between chronic allograft damage index score and MRI perfusion. MRI perfusion was significantly lower in the four patients with a chronic allograft damage index score of > 4 than in the other patients (1.94 vs 2.43 mL/min/g, respectively; p = 0.03). The effect size for this difference was large (d = 1.7). The R-2 for the linear regression model was 0.53. CONCLUSION. We observed an association between contrast-enhanced MRI renal perfusion and chronic allograft nephropathy severity. Further studies are needed to confirm this preliminary finding and to evaluate the role of contrast-enhanced MRI renal perfusion as a screening test for allograft dysfunction and potential utility in patient management.