Renal scintigraphy by DMSA: early or tardy imaging? Comparison of performances in the diagnosis of acute pyelonephritis in infants

Several authors suggest early imaging (around 4 h after injection) invoking feasibility and counting statistics. On the other side, the tardy images (> 12 h ) constitutes another approach based on two arguments: the fixation curve of DMSA is a plateau, on one hand, and one avoids the presence of circulating or still present DMSA in the interstitial spaces and pyelo-calyceal cavities, on the other hand. The aim of this work is to compare the performances of these two approaches in detecting focuses of acute pyelonephritis. One hundred infants (average age, 3.3 ± 3.6 years), with a suspicion of APN clinic and biologic affliction, benefited by a DMSA scintigraphy. In 89 cases, there was a first episode, while in 7 and 4, of the second and third episode, respectively. The scintigraphy was performed 2 days after the debut of urinary infection. The images were achieved 3 h ± 30 min and 18 h ± 1 h for every infant. The incidences were frontal-posterior in 2 cases, supplemented by right and left oblique-posterior, on the early films. The images were qualitatively analyzed by 2 observers recording the number, intensity and the defect size. The following results were obtained. The detection rate is of 66% for the 3 h images and 70% for the 18 h images. The images were considered as equivalent in 57% of cases. Particularly, the oblique-posterior incidences have not increased the rate of detection. In 30% cases the tardy images allowed a better detection of lesions, particularly, in 17% of cases where a higher number of lesions was detected (in 4 cases the focuses were evidenced solely on the tardy films). The early films were more contributive only in 11% of cases. For 3% of cases the detection of focus was due uniquely to the early oblique-posteriors. In conclusion, these results show the superiority of tardy films in detecting the lesions of pyelonephritis. They urge to realize images in these clinic indication not before at least 6 hours after injection