Urinary Carbohydrate Antigen 19-9 in Children with Unilateral Ureteropelvic Junction Obstruction: Does Bladder Urine...

Urinary carbohydrate antigen 19-9 (CA 19-9) has emerged as a promising noninvasive biomarker in the diagnosis of ureteropelvic junction obstruction (UPJO) in children. However, whether bladder urine reliably reflects biomarker concentrations in the renal pelvis remains uncertain. The aims are to evaluate the diagnostic utility of urinary CA 19-9 levels in children with UPJO and determine if bladder urine levels reflect those from the renal pelvis.

This prospective case-control study included 72 children from July 2023 to June 2024. The control group (n = 38) comprised asymptomatic children with normal ultrasound, while the UPJO group (n = 34) included children with unilateral UPJO requiring pyeloplasty. Urine samples were collected from the bladder in both the groups and from the renal pelvis during surgery in the UPJO group and analyzed for CA 19-9 concentration using enzyme-linked immunosorbent assay. Median values were compared using nonparametric tests.

There was no significant difference in age/sex distribution between the groups. Median CA 19-9 levels (U/mL) were significantly higher in the UPJO group (pelvic: 274.14; bladder: 281.22) compared to controls (3.78, P = 0.001). There was no significant difference between bladder and pelvis CA 19-9 levels in the UPJO group (P = 0.134). A moderate positive correlation was observed between pelvic and bladder CA 19-9 levels (r = 0.6055).

CA 19-9 levels in bladder urine are significantly elevated in children with UPJO and closely correlate with renal pelvic levels. These findings support the use of bladder sampling as a noninvasive test in diagnosing and monitoring UPJO, potentially simplifying clinical evaluation.