Relationships among nocturnal urinary volume, bladder capacity, and nocturia with and without water load in...

To evaluate the relationships among nocturnal urinary volume (NUV), bladder capacity, and nocturia in nonenuretic children with and without water load.

We evaluated 72 healthy nonenuretic volunteers. The NUV and bladder capacity were measured for 2 nights at volunteers' homes with and without water load.

Of the 72 nonenuretic children, 45 (63%) were classified into the large NUV group in which the NUV with water load was more than the upper limit of the 95% confidence interval of NUV in Japanese nonenuretic children, and the other 27 (37%) were classified into the small NUV group. In the large NUV group, 33 (73%) had one or two episodes of nocturia because of water intake, and 12 (27%) did not. The nocturnal bladder capacity in the latter 12 children was significantly larger than that in the former 33, although no significant differences were found in functional bladder capacity and NUV with water intake.

Most nonenuretic children were able to cope with the physiologic loading of water that would cause bedwetting in enuretic children. After water loading, three quarters of the nonenuretic children were able to awake easily because of the need to urinate with a certain volume of urine in the bladder, and the one quarter who did not awake were able to hold more urine in their bladder in the sleep state.