Technetium-99m dimercaptosuccinic acid scintigraphy studies of renal cortical scarring and renal length.

Abstract

The aims of this study were to validate 99mTc-dimercaptosuccinic acid (DMSA) scintigraphy appearances with histopathological features of scarring; to evaluate the sensitivity and specificity of 99mTc-DMSA and ultrasound for the detection of renal scarring; to compare planar, pinhole and SPECT techniques when using 99mTc-DMSA; and to compare 99mTc-DMSA and ultrasound renal length measurement. Reflux nephropathy was induced in large white pigs using established methods. To ensure that the abnormalities detected were scars and not inflammatory changes, the pigs were not studied until 3 mo after the treated episode of acute pyelonephritis confirmed by 99mTc-DMSA. Twenty pigs were enrolled in the study. Eleven reached the end point, but only nine pigs (18 kidneys) were available for analysis. Thirty-four scars were identified pathologically; 24 were present macroscopically and a further 10 were seen only on microscopy. Technetium-99m-DMSA abnormalities correlated with scars histopathologically with an accuracy of 92% versus that of ultrasound, 75% (p < 0.001). Technetium-99m-DMSA more accurately identified scarring with a higher sensitivity (76% versus 29%) and specificity (98% versus 92%) than ultrasound. On the 99mTc-DMSA study, pinhole imaging had the highest accuracy (92%) when compared with planar (90%) and SPECT (87%) data. These differences were not statistically significant. Renal lengths as measured on 99mTc-DMSA more closely correlated with length measurement at pathological examination than ultrasound. Technetium-99m-DMSA measurement was, on average, 6% higher than pathology, and ultrasound was, on average, 22% lower. Technetium-99m-DMSA appears to be the preferred method for the detection of renal cortical scarring and accurate renal length measurement when compared with ultrasound examination.