[Latent ureteric outlet stenosis in young adults - the diagnostic significance of functional assessment in cases of marked hydronephrosis].

Congenital ureteropelvic junction (UPJ) obstruction may remain clinically compensated until young adulthood despite prenatal or early childhood diagnosis. Distinguishing morphological hydronephrosis from functionally significant obstruction is crucial for therapeutic decision-making. Case: A 25-year-old woman was found to have mild right-sided pelvicalyceal dilatation as an incidental finding during a routine primary care evaluation. Several weeks later, following a urinary tract infection accompanied by flank pain, repeat imaging demonstrated marked progression of hydronephrosis. Further evaluation with computed tomography and Tc-99m-MAG3 renography revealed a urodynamically significant right-sided urinary outflow obstruction despite preserved split renal function. Owing to the documented progression, functional obstruction, and persistent urinary stasis, robot-assisted pyeloplasty was performed. Postoperatively, urinary drainage improved while renal function remained stable. Conclusion: In adults with hydronephrosis, therapeutic decisions should not be based solely on the degree of morphological dilatation. Clinical evolution and functional assessment of urinary drainage are essential for appropriate management.