LAUSR

OBJECTIVE Management of symptomatic ureteropelvic junction (UPJ) obstruction with hydronephrosis and discordant Tc-99 MAG-3 renal scintigraphy is challenging. Here we describe long-term outcomes of patients who underwent robot-assisted laparoscopic pyeloplasty for the correction of symptomatic UPJ obstruction with discordant pre-operative Tc-99m mercaptoacetyltriglycine (MAG-3) renal scintigraphy. METHODS Patients undergoing robot-assisted laparoscopic pyeloplasty for symptomatic UPJ obstruction at a single academic center from 2009 to 2021 were retrospectively reviewed. Patients were categorized into three groups with varying degrees of obstruction based on pre-operative MAG-3 imaging: Group 1- no obstruction (Lasix T1/2 clearance < 10 minutes), Group 2- equivocal obstruction (Lasix T1/2 clearance 10-20 minutes), and Group 3: obstruction (Lasix T1/2 clearance > 20 minutes. Pyeloplasty success was defined as resolution of symptoms and improvement/stable CT imaging or MAG-3 scintigraphy. Failure was defined as persistence of symptoms with either obstruction on functional imaging, worsening hydronephrosis, or subsequent intervention. RESULTS 125 cases were identified, with a median patient age of 35 years. Dismembered pyeloplasty technique was performed in 98.4% of cases. Median pre-operative split renal function on MAG-3 scintigraphy was the only statistically significant (p = 0.003) difference in pre-operative characteristics between the three groups. There were 15 post-operative complications, with a rate of Clavien-Dindo grade 3 or higher complications of 4.8%. Overall pyeloplasty success was 92.8%, with success rates of 100% (15/15) and 97% (32/33) in the no obstruction and equivocal obstruction groups, respectively. Median time to pyeloplasty failure was 20.4 months. CONCLUSION Robot-assisted laparoscopic pyeloplasty is a safe and effective surgical intervention for correcting UPJ obstruction. Patients with symptoms of UPJ obstruction and discordant functional imaging studies demonstrate similar or improved success rates after pyeloplasty when compared to patients with documented high-grade obstruction. Based on these findings pre-operative renal scan may not be reliable in appropriate selection of candidacy for successful pyeloplasty.