Respiratory Studies in Children: VI. Timed Vital Capacity in Healthy Children and in Symptom‐Free Asthmatic Children1

A study by means of micturition urethro-cystography of changes in the lower urinary tract and of the effective bladder capacity in children with nocturnal enuresis was performed on the basis of a randomly selected twin series. The material comprised 40 same-sexed twin pairs in which a t least one of the partners suffered from persistent nocturnal enuresis, i.e. 49 affected twins and 31 unaffected partners who were used as controls. 2. Only minor deviations in the lower urinary tract were found. The investigation failed to show any significant relationship between such deviations and noc turnal enuresis. 3. There seems to be no relationship between nocturnal enuresis and the width of the posterior urethra during micturition. 4. The statistical analysis indicates that there is no difference in the effective bladder capacity between children with persistent nocturnal enuresis and other children. 5. There seems to be no significant relationship between nocturnal enuresis and the occurrence of spina bifida occulta in the lower lumbar and sacral regions.