Clue Found to Persistent Bed-wetting

Dec. 1, 2006 -- Kids who continue to wet the bed even after drug treatment may have too-high levels of certain hormone-like substances, Danish researchers find.

The scientists are now studying whether giving kids a drug to block the substances, called prostaglandins, will work.

Bed-wetting isn't a serious medical condition. But for those who suffer from it, the humiliating condition can have serious emotional consequences.

While most kids eventually outgrow the problem, as many as one in 10 still wet the bed at age 7.

The condition also affects up to two in 100 adults.

DDAVP, a prescription drug that reduces urine production, stops most bed-wetting for 70% of kids. (The drug's generic name is desmopressin.)

Unfortunately, DDAVP doesn't work for 30% of kids.

Why? Konstantinos Kamperis, MD, PhD, and colleagues at Aarhus University Hospital, Denmark, decided to find out.

They studied 46 7- to 14-year-old boys and girls with treatment-resistant bed-wetting, and 15 age-matched kids who didn't wet the bed.

All the kids spent two nights in the hospital: The first night to get used to being there; the second hooked up to blood- and urine-collection devices.

The extensive equipment turned out to be worth the trouble.

Because of obvious difficulties in collecting nighttime urine from kids who wet the bed, most studies have examined first-morning urine as the closest substitute. That, Kamperis and colleagues find, is an error.

They found that the big urine differences between bed-wetters and nonbed-wetters occur in the first few hours of the night. At that time, treatment-resistant bed-wetters have high levels of sodium, urea, and prostaglandin in their urine.

It's likely this excess sodium is causing excess urine volume.

But the kids' diets had been controlled before the study, so the problem wasn't eating salty food.

Instead, Kamperis and colleagues suggest, these kids may have too-high prostaglandin levels.

The researchers are currently studying whether giving the kids indomethacin, a prostaglandin-blocking nonsteroidal anti-inflammatory drug (NSAID), will help.

The current study appears in the December issue of the American Journal of Physiology-Renal Physiology.

SOURCES: Kamperis, K. American Journal of Physiology-Renal Physiology, December 2006; vol 291: pp F1232-F12140. News release, American Physiological Society.