Classification of Tc-99m DTPA renograms based on the relationship between uptake and perfusion pattern

Various parameters can be derived from a renogram, but the relationship between uptake and perfusion pattern on Tc-99m DTPA time-activity curves has not been evaluated to date. A previous report documented sequential changes in the relationship between perfusion and uptake in renal transplant donors. The current study looked at serial changes in renogram patterns in kidneys exhibiting hyperfiltration. The aim was to reveal the pathophysiological significance of different perfusion-uptake patterns observed on Tc-99m DTPA renal scintigraphy.

Serial changes in two patient groups were evaluated: (A) renal transplant donors before, early after, and late after donor nephrectomy; and (B) renal transplant recipients at the initial and later stages of chronic allograft nephropathy (CAN). Quantitative scintigraphic parameters included: the ratio of peak perfusion counts to plateau counts (P:PL); the ratio of counts at peak perfusion to counts at peak uptake (P:U); and the glomerular filtration rate. The effect of background selection on the parameters, P:PL and P:U, was evaluated using three different background regions of interest.

Each group in the study exhibited a different renogram pattern. Based on these results, renograms were classified into six patterns. Compared to the preoperative findings, P:U and P:PL increased significantly early after the operation. Late after the operation, P:U decreased significantly compared to both pre- and early postoperative values. In patients at the early stages of CAN, both P:PL and P:U were lower than normal. During the later stages of CAN, perfusion and uptake peaks were absent.

Our results identified several different renogram patterns that were thought to correspond with hyperperfusion, hyperfiltration, increased intraglomerular pressure, and glomerulosclerosis. The ratios of P:PL and P:U underwent significant change under conditions that affected kidney hemodynamics and function.