In this study, the investigators aim to evaluate the role of urinary ATP as a biomarker for the diagnosis, treatment, and follow-up of OAB in children for the first time in a clinical investigation, as previous research has been limited to adults.

The diagnosis of OAB primarily relies on **medical history** and **physical examination**. Diagnosis is supported by appropriate laboratory findings and imaging methods. The role of various urinary biomarkers has been investigated as a non-invasive and simple diagnostic method. In recent years, research has focused on several biomarkers, particularly low-grade inflammatory mediators such as cytokines, Prostaglandin E2 (PGE2), Nerve Growth Factor (NGF), and Brain-Derived Neurotrophic Factor (BDNF). However, although these biomarkers are correlated with the severity of OAB symptoms, no studies have demonstrated their independent prognostic value.

For example, some studies report significant variability in urinary NGF levels, with not all patients showing increased urinary NGF. Other studies have noted that NGF correlates with OAB symptoms and decreases significantly after treatment. Consequently, no biomarker has yet been defined for routine clinical use. Moreover, biomarker studies specifically targeting pediatric OAB are limited, with most research focusing on adult populations and extrapolating findings to children.

Today, there is growing recognition of the role of purinergic transmission in urinary dysfunction. Purinergic transmission involves both afferent and efferent pathways in bladder emptying and has been implicated in the pathogenesis of detrusor overactivity (DO). In vitro studies have demonstrated that bladders with DO release higher amounts of Adenosine Triphosphate (ATP) from urothelium and cholinergic nerve terminals compared to normal bladders. Clinical studies suggest that urinary ATP levels could serve as a potential biomarker for OAB in adults. However, our literature review revealed that this biomarker has not yet been evaluated in children with OAB.

In this study, the investigators aim to evaluate the role of urinary ATP as a biomarker for the diagnosis, treatment, and follow-up of OAB in children for the first time in a clinical investigation, as previous research has been limited to adults.

Two midstream urine samples will collected from the OAB group: one pre-treatment and one at the first month of anticholinergic treatment. Urine samples will centrifuged, stored at -80°C, and ATP levels will measure via ELISA. Comparisons will make between the groups and pre-/post-treatment ATP levels in the OAB group. Correlation analysis will conduct between ATP levels and lower urinary system (LUS) parameters.

Inclusion Criteria:

• The patient is under 18 years of age
• OAB symptoms may be accompanied by frequent urination, urgency, and urinary incontinence

Exclusion Criteria:

• Neurological disease
• malignancy
• active urinary tract infection
• bladder anomaly (uroterocele, diverticulum),
• LUS obstruction, ectopic ureter
• history of previous urological surgery