Quantitative Renal Scintigraphy for Differentiating Ischemic and Nonischemic Transplant Complications: A Biopsy-Controlled Study.

Abstract

Objectives: Tc -99m -diethylenetriaminepentaacetic acid renal scintigraphy is a noninvasive method for assessment of graft function. Here, we evaluated the diagnostic accuracy of quantitative scintigraphy parameters in differentiating ischemic complications (acute tubular necrosis ) from nonischemic complications (acute rejection, tubulointerstitial nephritis ), using tissue biopsy as the reference standard.

Materials and methods: We retrospectively analyzed 63 kidney transplant recipients who underwent Tc -99m -diethylenetriaminepentaacetic acid renal scintigraphy followed by renal biopsy within 6 months posttransplant. Quantitative parameters derived from time -activity curves included delta peak, peak perfusion activity, plateau perfusion activity, peak perfusion activity -to -plateau perfusion activity ratio, peak function activity, peak perfusion activity -to peak function activity ratio, and the 20 /3 ratio. We compared scintigraphy findings with biopsy results categorized as ischemic, nonischemic, or normal. For statistical analysis, we used the Mann -Whitney test and receiver operating characteristic curve analysis.

Results: Of the 63 patients, 59 had abnormal biopsy findings (5 ischemic, 54 nonischemic ). Scintigraphy findings were concordant with biopsy results in 61 cases. Delta peak (P = .043 ) and peak perfusion activity -to peak function activity ratios (P = .015 ) differed significantly between ischemic and nonischemic groups. Receiver operating characteristic curve analysis showed that delta peak was a good predictor of nonischemic complications (area under curve = 0.772 ), whereas peak perfusion activity -to peak function activity ratio was a strong predictor of ischemic complications (area under curve = 0.822 ). A delta peak cutoff value of 6.5 seconds yielded 63 %sensitivity and 80 % specificity for identifying nonischemic complications, whereas a peak perfusion activity -to peak function activity ratio cutoff of 1.31 provided 80 % sensitivity and 82 % specificity for detecting ischemic complications.

Conclusions: Quantitative parameters derived from Tc -99m -diethylenetriaminepentaacetic acid renal scintigraphy are useful for differentiating ischemic from nonischemic renal transplant complications and correlate well with biopsy findings. These parameters may aid in the early diagnosis and management of posttransplant graft dysfunction.