A new renogram obtained by adding post-micturation images on the diagnosis of obstructive uropathy

Abstract

The aim of this study was to evaluate the diagnostic input of the renal washout percentage and the extended renogram curve which was obtained by quantifying the data of post voiding dynamic images. Sixtysix kidneys of 54 patients (11 female and 43 male; age 1 month- 72 years ) with T max1/2 values >10 minutes (min) in the diuretric renography (group 1: 1/2 > 20 min and group 2: Tmax 1/2 between 10-20 min) were enrolled for the study. The kidneys in group 1 were also divided into 2 groups according to differential renal functions (group 1A >40%: group 1B <40%). Just after the first dynamic imaging, two additional post-voiding dynamic images using the same acqusition parametres (15 sec/image; 128*128), as the first imaging, were obtained for all patients. The original (R30) and extended renogram curves (Rek) were generated in the excell programme by using the background and decay corrected total counts of each kidney obtained from the data of dynamic acquisitions. The renal washout percentages at the first 30 minutes (min) acquisition (BY 30), the first (BYekl) and the second (BYek) post-voiding imaging were also calculated. The washout percentage of <50% was accepted as obstruction. In group 1 (45 kidneys), the evaluation of wash-out percentages in the first 30 minutes dynamic images, the first and the second post-voiding images revealed obstruction in 43, 34 and 22 kidneys respectively. While the the original renogram curve (R30) showed obstruction in 43 kidneys, the extended renogram curves (Rek) showed obstruction in 31 kidneys. The difference between BY30, BYek1ve BYek2 values in group 1 were found statistically significant (p<0,001). In group 2 (21 kidneys), the evaluation of wash-out percentages in the first 30 minutes dynamic images, the first and the second post-voiding images revealed obstruction in 3, 1 and 1 kidneys respectively. Thirteen kidneys of R30 and 10 kidneys of Rek showed obstructive renogram patern. The difference between BY 30 and BYek1 (p<0,01), BY30 and BY ek2 (p<0,001), BYek1 and BYek2 (p<0,001) values in group 2 were found statistically significant. Eleven kidneys in group 1A and 10 kidneys in group IB revealed obstruction in the evaluation of BY ek values (p<0,01 ve p<0,05). During the study period, 11 kidneys in group 1 and 1 kidney in group 2 were operated in which 8 kidneys revealed UP narrowing, 1 kidney revealed compression of aberant fibrotic band, 1 kidney revealed aberant renal artery and 2 kidneys revealed ureterocel. The scintigraphic analysis of only 8 kidneys supported obstruction. Seven kidneys came for control scintigraphy and non of them demonstrated >10% difference at split renal function during follow up. Obtaining the post-voiding images in a dynamic format allowed us to perform extended renogram and to calculate the renal washout percentages. Although the number of surgically diagnosed patient is not sufficient to get a definitive conclusion, the renal washout percentages and the extended renograms will contribute additional information in the diagnosis of obstructive uropathy.