This prospective, randomized, 3-arms, parallel-design, controlled clinical trial is conducted to determine whether high dose vitamin D supplementation (combined with standard urotherapy ) improves outcomes, compared with solifenacin (combined with standard urotherapy ) ,and standard urotherapy alone in children with OAB dry.

Overactive bladder(OAB), characterized as urinary urgency accompanied in many instances by frequency and sometimes nocturia, with or without urinary incontinence, in the absence of urinary tract infection or other documented pathology, is a common clinical entity in pediatric urology. The majority of patients with OAB do not experience incontinence yet suffer from symptoms of urgency, frequency, and nocturia, which has been termed OAB dry. Currently, standard urotherapy is proposed as the first-line therapeutic options and adjunctive anticholinergics are usually used when urotherapy alone failed. Behavioral therapy often fail to achieve satisfied symptom control as children's poor compliance. In addition,adverse side effects such as dry mouth, constipation, gastro-oesophageal reflux result in early pharmacologic treatment discontinuation.

It was informed that patients with OAB are more likely to suffer from vitamin D deficiency. The aim of the study is to determine the effect of vitamin D supplementation as an adjunctive therapy to behavioral therapy in the treatment of OAB dry. Eligible patients aged 5-18 years with a diagnosis of OAB dry will be randomly assigned into three groups to receive high dose vitamin D supplementation (combined with standard urotherapy ) , solifenacin (combined with standard urotherapy ) or standard urotherapy alone. Serum levels of 25(OH)D will be measured at baseline. Symptoms severity will be assessed at baseline and followup. All the other sociodemographic data will be also assessed. The study will give more information on the application of vitamin D supplementation in the management of OAB dry.

Inclusion Criteria:

1. Children older than 5 years of age with a diagnosis of OAB dry (do not experience incontinence yet suffer from symptoms of urgency, frequency, and nocturia) seen at the outpatient urology clinics (diagnosis follows the latest International Children's Continence Society recommendations).
2. Children with a serum vitamin D level of less than 35 ng/ml as indicated by the laboratory result.
3. Written informed consent was obtained from participants and their parents. -

Exclusion Criteria:

1. Those with a comorbidity of other urological abnormalities or serious diseases (e.g. hypospadias, cryptorchidism, posterior urethral valves, vesicoureteral reflux, neurogenic bladder, urological tumours, urinary stones, bladder and urethral injuries, etc.).
2. Those with a comorbidity of neurological disorders (e.g. epilepsy, spinal cord injury, spinal cord dysplasia, spinal cord embolism syndrome, multiple sclerosis, autism spectrum disorder, etc.) .
3. Those with acomorbidity of severe heart disease, abnormal liver or kidney function, lung disease, skeletal deformities, severe gastrointestinal disease, or inherited metabolic disorders.
4. Those with a history of gastrointestinal surgery and urinary tract surgery.
5. Those with chronic constipation.
6. Those taking anticonvulsant and antiepileptic drugs, hormones, anti-tuberculosis drugs.
7. Those have a previous history of hypercalcemia, hyperphosphatemia with renal rickets.
8. Those have a history of haematuria and urinary tract infection within the last 1 year.
9. Those have a history of allergy or allergic disease to vitamin D preparations.
10. Those Participate in other clinical studies at the time of consultation or during the follow-up of other clinical studies.
11. Any condition that could cause urinary symptoms or interfere with assessment of efficacy parameters.
12. Those unwilling to participate in this study. -

Apart from the participant's personal information.

8 weeks

Apart from the participant's personal information

outcome evaluators, and statisticians were blinded.