The finding may help physiologists understand why about 30 percent of children who suffer from bedwetting (nocturnal enuresis) don't respond desmopressin, which is commonly used to treat the condition, the University of Aarhus researchers said.

Nocturnal betwetting affects between 7 percent and 10 percent of 7-year-old children, although cases have been seen in older and younger children.

In one group of children studied, researchers found that the urine contained more sodium, urea and prostaglandin. Because the level of sodium and was higher, the volume of urine expanded in the bladder, leading to enuresis, the researchers said.

The increased prostaglandin production could account for the difference in the levels, the researchers said.

The researchers started treating the children who didn't respond to desmopressin with a prostaglandin inhibitor. Those trials are expected to be completed within a year.