Objectives: To evaluate children with refractory monosymptomatic nocturnal enuresis to determine whether detrusor overactivity (DOA) plays a role in 4 weeks of unsuccessful treatment with retention control training (RCT); whether an increase in bladder capacity can eventually be obtained by RCT plus oxybutynin; and whether the increase in capacity is the primary key to success.
Methods: Sixty-eight children with refractory monosymptomatic nocturnal enuresis were included. They all had a maximal cystometric capacity less than the age-expected value. RCT was done by water loading and retention to the point of urgency once daily. During training, changes in bladder capacity were evaluated by voiding charts. If after 4 weeks of RCT, less than a 10% increase in bladder capacity was noted, oral oxybutynin was added.
Results: The incidence of DOA was 66%. After 4 weeks of RCT, the bladder capacity increased in 20.6%. Combining RCT with oxybutynin led in the end to normalization of the bladder capacity in 79.4%. Older age and high-pressure DOA negatively influenced the ability to increase the bladder capacity. Fifteen children became completely dry, mainly by converting enuresis to nocturia.
Conclusions: Unsuccessful RCT is often caused by DOA, especially if a bladder capacity rise of at least 10% cannot be achieved within 4 weeks. If oxybutynin is added to the treatment, normalization of bladder capacity can be obtained in most. This increased bladder capacity cures enuresis only in a minority by sharpening their arousal and provoking nocturia.