The Significance of Tc-99m DTPA Renal Scintigraphy for the Demonstration of Progressive Functional Changes That Accompany Chronic Allograft Nephropathy

ObjectivesChronic allograft nephropathy (CAN) is usually progressive; its natural course can only be modified in the initial stages. In this study, we graded Tc-99m diethylenetriaminepentaacetic acid (DTPA) renogram curves with respect to the perfusion/uptake pattern and correlated these findings with biopsy results in patients with CAN.MethodsThis study included 63 renal allograft recipients with biopsy-proven CAN. The agent used for renal scintigraphy was Tc-99m DTPA. Quantitative evaluation of perfusion included calculation of the ratio of peak perfusion counts divided by plateau counts (P:PL). Deterioration of renal function was accompanied with a gradual loss of a peak and plateau pattern. For the evaluation of uptake in relation to perfusion pattern, we graded the renogram curves into four based on the presence of a peak and plateau pattern and the presence of an uptake peak.ResultsIn patients with CAN, the mean P:PL was significantly lower than that of the control group. The serial changes in successive grades of CAN in respect to uptake-perfusion pattern was a gradual loss of peak and plateau pattern followed by a decline in uptake. In recipients with high-grade CAN, an uptake peak was absent.ConclusionsEvaluation of Tc-99m DTPA time-activity curves revealed a progressive change in perfusion-uptake pattern in patients with CAN. According to our results, deterioration of perfusion preceded the decline in uptake. Serial renogram changes are thought to reflect initial hypoperfusion followed by increased intraglomerular pressure and finally glomerulosclerosis. These findings have implications for the pathophysiology and management of CAN.