Determinants of nocturnal enuresis in homozygous sickle cell disease.

The determinants of nocturnal enuresis in homozygous sickle cell (SS) disease have been investigated in 16 enuretic and 16 age and sex matched non-enuretic children. Overnight fluid deprivation tests (8pm-8am) demonstrated no significant difference in maximum urine osmolality or urine volumes, although the latter tended to be higher in the enuretic children. Maximum functional bladder capacity, estimated by maximum voided volume during oral fluid loading, was lower and the ratio of overnight urine volume to maximum functional bladder capacity higher in the enuretic than the non-enuretic group. Enuretic children were more likely than non-enuretics to be considered deep sleepers by their family. High urine volumes may contribute to nocturnal enuresis in SS disease, although the similar values in enuretic and non-enuretic children implies that additional factors determine the presence of enuresis. Low maximum functional bladder capacity, and a high ratio of overnight urine volume to maximum functional bladder capacity, appear to be important determinants.