Parents of newly toilet-trained boys should take a few simple steps to keep their sons' penises safe when they go to the bathroom, a team of UK urologists advises.

There's evidence that crush injuries due to falling toilet seats may be on the rise, Dr. Joe Philip of Leighton Hospital in Crewe and colleagues warn in a letter in BJU (British Journal of Urology) International.

While he and his colleagues typically see just one or two such cases a year, if any, Philip told Reuters Health, they treated four different two- to four-year-old boys with penile crush injuries in the past several months.

"Thankfully all of the four had only the foreskin swelling, but obviously there's a lot of anxiety for the parents and the kids," Philip said. All of the boys were kept in the hospital overnight until they were able to urinate, but none of them suffered lasting physical damage, he added.

In each case, the youngster was trying to urinate on his own and had lifted the toilet seat, only to have it fall back down. An industry report states that wooden toilet seats are becoming more popular as a possible explanation for the increase in injuries.

Philip and his colleagues offer the following tips to help families of young boys prevent these injuries from happening:

Install "soft fall" toilet seats in every bathroom in the home, and ban heavy toilet seats made of wood or ceramic from homes with young boys.

Leave the toilet seat up at all times, until all of the boys in the household can hold the seat up on their own.

Supervise children every time they visit the bathroom.

Constant supervision can be difficult, Philip conceded, especially during holiday gatherings when a youngster may steal off on his own to demonstrate his newly-found skill. "Children want to show that they are independent," he said.