Discrepancy of measured renal length between ultrasonography and dimercaptosuccinic acid (DMSA) scintigraphy

Purpose: An inter-observer variability exists in the measurement of the renal length during ultrasonography, but dimercaptosuccinic acid (DMSA) scintigraphy allows greater objectivity. Thus, the aim of this study was to evaluate the discrepancy of the renal length measured using the two methods. Materials and Methods: Between January 2003 and June 2005, 249 consecutive patients underwent DMSA scintigraphy and ultrasonography. Due to the exclusion of kidneys where a photon defect was observed during DMSA scintigraphy, the number of kidney enrolled in this study was 439. The renal length measurements in any plane were longest using ultrasonography. The renal lengths were measured using DMSA scintigraphy by assessing the maximum pixel length, which was then converted to centimeters. Results: The mean renal lengths measured by DMSA scitigraphy and ultrasonography were 8.06±1.49 and 6.80±1.38cm, respectively. The mean difference in the renal length measured between the two methods was 1.26±0.84cm. The sonographic renal length was significantly shorter than that found via scintigraphy (Student's t.-test, p < 0.001). Conclusions: Our results were similar to those of previously reported Studies, where the scintigraphic renal length exceeded that obtained sonographically. Due to the possibility of underestimating the renal length when using ultrasonography, clinicians inust be cautious when following up pediatric patients using ultrasonography.