Every man’s stream fires off in an unintended (and sometimes, horribly unfortunate) direction from time to time. But what’s actually causing that to happen? According to Adrienne Carmack, board-certified urologist and author of The Good Mommy’s Guide to Her Little Boy’s Penis, complications caused by circumcision (or other surgeries on the penis) are a major contributor.

“I’ve only ever seen this as a regular problem in men who’ve had some sort of surgery on their penis — be it circumcision or a surgery for hypospadias [that is, when the opening of the penis is on the underside rather than the tip],” explains Carmack, speaking from her experience on the board of health professionals for Intact America, the nation’s largest anti-circumcision advocacy group.

Research agrees with Carmack: A recent study that reviewed hospital records of more than four million males in Denmark from 1977 to 2013 found that as many as one in five circumcised boys and men can’t urinate normally. This is because circumcision removes the penis’ natural protection against meatal stenosis — the pathological narrowing of the urethral opening, which can also cause reduced stream, urgency and frequency of the need to urinate, blood in the urine and involuntary urination.

“Anything that narrows the urethra can cause the urine stream to deflect — think of it like a kink in a water hose — and the most common cause of that is surgery on the penis,” explains Carmack, who found similar results during a study she published in the International Journal of Human Rights. In other words, if your stream never seems to hit its target (and you’re experiencing other urine-related difficulties like those mentioned above) it’s a good idea to get checked for meatal stenosis.

Of course, there are simpler reasons why your stream isn’t always straight. “If a man who has a normal, intact penis without any issues experiences this from time to time, it’s probably related to how badly he has to pee or how much urine he has to get out,” Carmack says. “If you’re urinating with low-pressure [because you don’t have to pee all that badly], it’s way more likely for the stream to deflect.” This goes back to her water hose analogy — the less pressure behind the stream, the less likely it will shoot out in a straight line.

It should also be noted that obstructions within the urethra — like, for instance, dried semen — can cause your stream to divert, for obvious reasons, until they’re pushed out. If that’s the case, don’t panic — just be prepared to mop the floor every once in awhile.