ABSTRACT
Obstructive pattern within hydronephrotic non-obstructed kidney is frequently encountered during [99m] TCMAG3 diuretic renography. The aim of this study was to assess the value of applying new protocol and criteria on dual-time imaging in ruling out obstruction. We included 53 children [56 kidneys] in this study [28 boys and 25 girls with age range three weeks to 12 years]. All had hydronephrosis, which was bilateral in three children. Eighteen children had pyeloplasty, while 35 children had no previous surgical interventions. All children were referred for assessment of renal outflow obstruction and kidney function. All children underwent routine diuretic [99m]Tc MAG3 renal renography. All had obstructive patterns during diuretic [99m] TcMAG3 renography and underwent a second dynamic study 30 minutes later for 10 minutes. Non obstructive criteria were set as down sloping second time renogram with drop of kidney counts by 50% of peaked activity in first time renogram. Obstructive criteria on dual-time imaging were set as progressive rising second time renogram or flat second time renogram with drop of kidney counts by less than 30% compared to first time study. Equivocal criteria were set as flat renograms with drop of kidney activity by 3 0-50% or down sloping renogram with drop of kidney counts by<30% over 10 minutes. Non obstructive patterns were noticed in 16 kidneys 15 [patients], with down sloping curves during second time renograms in seven kidneys and flat second time renogram with drop of activity by> 50% in 9 kidneys. Obstructive patterns on dual time point [99m] TcMAG3 renography were noticed in 31 kidneys [29 patients]. Eleven kidneys [six patients] were false positive, since three patients had neurogenic bladder with no obstruction, two patients had long standing severe hydronephrosis with no obstruction and one patient had glomerulonephritis. Equivocal patterns were noticed in nine patients, four of them were turned to have significant obstruction, while five had no obstruction. Dual-time [99m] Tc-MAG3 diuretic renography can increase the efficiency in differentiating between obstructed and non-obstructed hydronephrosis compared to routine single time study