Robot-assisted advancing spiral flap pyeloplasty for complex ureteropelvic junction obstruction and ureteral atresia: a preliminary experience in 27 patients

BACKGROUND: Long-segment ureteropelvic junction obstruction (UPJO) (typically 12≥3 cm) and ureteral atresia present major reconstructive challenges due to fixed-length limitations of conventional flap techniques. This study evaluates the feasibility and safety of a robot-assisted advancing spiral flap pyeloplasty (RASFP) with dynamically adjustable flap design as a proof-of-concept for complex cases. METHODS: A single-center retrospective study (August 2022-July 2025) included 27 patients with long-segment UPJO (median stricture length 3 cm) or ureteral atresia. All patients underwent RASFP using two intraoperatively tailored flap configurations (anterograde/retrograde) without pre-determined length constraints. Primary outcomes were feasibility and safety; secondary outcomes included functional, radiological, and clinical improvement. RESULTS: All 27 procedures were completed robotically without conversion or major complications (Clavien-Dindo ≥II). The technique successfully managed all six ureteral atresia cases without grafts and bridged a 7-cm stricture. At median follow-up of 14 months, symptomatic relief was achieved in 88.9% of patients, and median hydronephrosis diameter decreased from 3.8 cm to 2.0 cm (P=0.01). Median eGFR increased by 1.6 mL/min. In complex cases (stricture ≥4 cm, atresia, or redo pyeloplasty, N.=16), clinical symptom relief was achieved in 87.5% (14/16) and radiological improvement in 81.3% (13/16). Postoperative CT urography in four patients confirmed obstruction relief in three. CONCLUSIONS: In this preliminary series, RASFP demonstrated acceptable safety and feasibility for carefully selected patients with complex UPJO and ureteral atresia who have a dilated renal pelvis. The technique may offer a potential tissue-sparing option for ultra-long strictures and atresia where conventional flaps may be inadequate. Comparative studies are needed to establish its relative efficacy.