The aim of this study is to investigate whether the voided urinary, perineal/preputial, and the fecal microbiota are different between children suffering from Overactive Bladder (OAB) and Daytime Urinary Incontinence (DUI) compared to age- and gender-matched healthy children without bladder symptoms. Moreover, the study aims to investigate if the microbiota is different according to the severity of DUI and if the microbiota is changed throughout treatment of DUI. A follow-up study will as well be performed on healthy children to investigate how the microbiota evolves with increasing age and pubertal stage. Children with OAB and DUI will be recruited from involved pediatric departments, and specimen in the form of urine, perineal/preputial swabs, and feces will be collected according to the protocol.

In Denmark, Daytime Urinary Incontinence (DUI) affects up to 22 % of children aged 5-7 years and 4.5 % of children aged 11-15 years. The most common cause of DUI is an idiopathic overactive bladder (OAB), leading to urgency (sudden desire to void) and frequency (frequent urinations). The cause of OAB among children and adolescents is not yet fully understood, however, studies among adults suggest dysbiosis of the voided and fecal microbiota as a possible explanation of OAB and DUI. This possible explanation is strengthen by the overlap in the symptomatology of OAB and urinary tract infections. Whether a different bacterial composition of the voided urinary, the perineal/preputial, and the fecal microbiota is evident for children with OAB and DUI compared to healthy children without bladder symptoms is yet to be elucidated.

The objectives of the present study are to investigate

1. if the bacterial composition of the voided urinary, the perineal/preputial, and the fecal microbiota differs between children with OAB and DUI and healthy children without bladder symptoms.
2. if the bacterial composition of the voided urinary, the perineal/preputial, and the fecal microbiota differs according to the severity of DUI.
3. if the bacterial composition of the voided urinary, the perineal/preputial, and the fecal microbiota alters concurrently with the treatment of DUI.

Moreover the objective of the study is to investigate how the microbiota changes with increasing age and pubertal stage.

Methods:

The study consists of three sub-studies. Sub-study one is a cross-sectional study comparing the microbiota of children with OAB and DUI and healthy children. The two other sub-studies are cohort follow-up-studies investigating the microbiota of children with OAB and DUI and healthy children without bladder symptoms, respectively. Seventy children with OAB and DUI and 40 healthy children without bladder symptoms will be recruited. Besides specimen collection (urine, swabs from the perineum (girls) and preputium (boys), and feces), the study participants and/or their parents are asked to fill in questionnaires, frequency and volume charts, and Dry Pies.

All children participating in the first sub-study are invited to enter the cohort follow-up-study. From participants with OAB and DUI willing to enter the follow-up-study, urine samples, swabs from the perineum/preputium, and fecal samples will be collected before initiating a new treatment modality of daytime urinary incontinence, and healthy children will be invited to a follow-up every 6 months until adulthood.

Inclusion Criteria:

• Overactive bladder as per International Children's Continence Society criteria (cases only).
• At least two wet days per week (cases only).
• No prior pharmacological treatment of OAB and DUI (cases only).
• No lower urinary tract symptoms (healthy participants only).
• Negative urine dipstick test

Exclusion Criteria:

• No known urogenital abnormality affecting the lower urinary tract function.
• No known gastrointestinal or neurological diseases.
• No use of systemic drugs within five half-lives of the drug.
• No use of systemic antibiotics within three months before inclusion
• No current urinary tract infection.
• No urinary tract infection within the last three months prior to inclusion.
• No current constipation.
• Abnormal uroflowmetry (healthy participants only).

The study population consists of 70 children with overactive bladder and daytime urinary incontinence and 40 healthy children without bladder symptoms. Children with OAB and DUI will be recruited from the involved pediatric departments, whereas healthy children without bladder symptoms will be recruited from the community.