Is there an anatomical problem involved in bedwetting?

Usually not. So-called primary enuresis (never routinely dry) typically runs in families and is more common on males than females. It is thought to involve slow maturation of part of the brain related to sleep. Secondary enuresis, that is bedwetting in someone who was dry routinely, can involve a physical problem such as a urinary tract infection but more often is stress-related.
Unlikely, if a child. A child with primary enuresis (meaning he's always been a bed-wetter) rarely has an anatomical problem. Primary bed-wetting runs in some families, and is a developmental problem that children will outgrow. If older than 7 years, a child can do a trial of DDAVP (desmopressin) tablets, which may decrease of stop it (after being seen by a pediatrician to make sure there isn't another medical cause for bed-wetting).