Evaluation of quantitative magnetic resonance imaging as a noninvasive technique for measuring renal scarring in a rabbit model of antiglomerular basement membrane disease.

Renal function tests are an insensitive means of detecting progressive scarring of the kidney such as occurs in chronic allograft rejection and lupus nephritis. Alternative approaches for the measurement of small progressive changes in renal structure on a repetitive basis are needed. Quantitative magnetic resonance imaging (proton T1 relaxation time) was assessed for this purpose. A rabbit model of antiglomerular basement membrane disease that develops glomerular and interstitial inflammation followed by scarring of the renal cortex was used. Longitudinal studies of cortical T1 showed a marked prolongation of T1 during the initial inflammation and edema associated with glomerular crescent formation (Day 7). The T1 remained prolonged up to Day 120 in animals with significant fibrosis and crescent formation when the wet/dry weight ratio (a measure of edema) had returned to baseline. T1 was a more sensitive index of renal injury than was serum creatinine for all of the end points measured (cortical hydroxyproline per dry weight, percent crescent formation, or histologic fibrosis score). It was concluded from these studies that measurement of renal cortical T1 is quite a sensitive index of renal injury, probably more sensitive than the measurement of serum creatinine, but that this method does not discriminate between edema and scarring.