Q: Why does my son’s urine go all over the place?

You’re changing your baby’s diaper and, without warning, his urine starts to geyser. You reach madly for a baby wipe or towel or anything nearby to contain this phenomenon, which scientists call a splayed urinary stream.

Here are some of the reasons this happens, to babies and also older boys:

• Meatal stenosis. For circumcised boys, chronic irritation from sitting too long in wet diapers can cause the hole where urine comes out to narrow. This can give the urine stream some altitude.
• Phimosis. The inability to push back the skin from the head of the penis sometimes causes a splayed urinary stream.
• For older boys, underwear sometimes pinches the urethra, which is the tube that brings urine from the bladder. The best fix? Boys can pull their underwear down when urinating, he says.
• Hypospadias. This rarely happens, but the urethra can open on the underside of the penis, and not at the tip. Circumcising your son is not recommended if you suspect he has this condition. The surgeon will likely use the extra foreskin when he or she fixes the problem.

Pediatric urologist Jeffrey Donohoe, MD