Posterior urethral valve is the main cause of bladder outlet obstruction in male infants and the most common cause of obstructive uropathy leading to chronic renal failure and end-stage renal disease in children.The incidence of posterior urethral valve is approximately 1:7,000-8,000 live births.

Posterior urethral valve is the main cause of bladder outlet obstruction in male infants and the most common cause of obstructive uropathy leading to chronic renal failure and end-stage renal disease in children.The incidence of posterior urethral valve is approximately 1:7,000-8,000 live births.

Anatomically, it is a membrane starting at the verumontanum and attached distally in the posterior urethra in the male child, resulting in valve like obstruction to the urine outflow leading to harmful effects on the urinary bladder and the upper urinary tracts.

Initial management of children with posterior urethral valves is immediate bladder drainage followed by endoscopic posterior urethral valve ablation. However, despite the early relief of bladder outlet obstruction, remaining pathological changes in the urinary bladder can lead to significant bladder dysfunction which leads to impaired upper tract drainage; valve bladder syndrome.

Oxybutynin is primarily indicated for the treatment of overactive bladder syndrome. It is still the most widely prescribed drug for overactive bladder in the world. It has been demonstrated to be safe for administration in the paediatric neurogenic bladder population.

Mirabegron, a beta-3 adrenergic agonist has been used for the treatment of overactive bladder symptoms as an alternative to anticholinergics with minimal side effects. Few studies stated safety of mirabegron in pediatric population with overactive bladder.

Inclusion Criteria:

- All children older than 3 years old who have undergone posterior urethral valve ablation

Exclusion Criteria:

• Children younger than 3 years old.
• Children with residual valve.
• Children who had undergone urinary diversion (vesicostomy or ureterostomy).
• Children with other conditions that can potentially affect upper or lower urinary tract function (spina bifida, anorectal malformation,prune belly syndrome).