Value of increase in bladder capacity in treatment of refractory monosymptomatic nocturnal enuresis in children

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. 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. 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. 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.