Urinary Incontinence: Why Does Bladder Leakage Happen?

Incontinence can be frustrating, confusing, and let’s be honest — a little taboo to talk about. But it’s way more common than most people think.

In this blog, we’re diving into urinary incontinence in the context of an overactive bladder, what causes leakage (even if you’re not currently leaking!), how a pelvic physiotherapist assesses it, and some of the lesser-known contributing factors — from urethral strength to bladder prolapse and hormonal changes. Understanding why leakage happens is the first step in getting the right help — and yep, we’re here for that.

Woman in activewear mid-run, representing bladder leakage during high-impact movement

What is urinary incontinence?

In the context of an overactive bladder, Overactive Bladder (OAB) wet differentiates itself from OAB dry by having urinary incontinence with the urgency episodes. It might occur multiple times a day, every few days or very infrequently. Some people stop it from occurring by going to the toilet more regularly (urinary frequency). If you manage your bladder habits to stop leakage from occurring, then this is OAB wet (yes, even if you don’t leak anymore).

What causes urinary incontinence?

OAB wet, or any form of urinary incontinence, involves dysfunction in the muscles around the urethra and sometimes the pelvic floor muscles. Now the urethral muscles give us majority of the closure, and the pelvic floor muscles assist against increases in abdominal pressure (like coughing/sneezing). So the pelvic floor muscles are not a huge contributor to stopping urge incontinence. This is why some people can be confused as their pelvic floor muscles function well, but they still have incontinence episodes.

The urethra has a few different sphincter muscles wrapping around it to keep it closed during bladder filling. If the abdominal pressure or bladder pressure increases, the urethral muscles must be strong enough to not be overpowered. If the muscles are weaker, then they’re easily overpowered and can cause leakage. Sometimes its just mild weakness, and a small amount of incontinence happens, and sometimes the weakness is more profound. These people tend to leak more often and at higher volumes.

How can a pelvic physiotherapist assess the cause of urinary incontinence?

With the urethral muscles, we can’t assess them like we can the pelvic floor muscles (through a pelvic/vaginal exam). It has been found that the best test we have for urethral strength is the urine stream stop test. With this test, you must ensure your bladder is moderately full (at least 200mLs but better being 300+mLs). When you’re on the toilet, start the stream and wait around 5 seconds until the stream is strong. Attempt to stop the stream. If you can fully stop it within 2-3 seconds (no dribbling) then this indicates great strength. If you can stop it but dribbling occurs for another 1-3 seconds then there’s likely some weakness, and if you can’t stop the stream then moderate weakness is likely present. Having weakness or difficulty with this doesn’t always result in leakage but can be linked to the development of leakage with aging. You’ll understand more about why people might not leak even with urethral weakness when we go through stress incontinence more (leaking with sneeze/cough/exercise).

Now this test does have its drawbacks. The time of day, how full your bladder is, how fatigued the body is and how active you’ve been during the day can contribute to the effectiveness of this test. I have some people who easily pass this test but still have leakage, so let’s chat about other contributing factors that can contribute to the leakage, not just urethral muscle weakness.

Is urinary incontinence hereditary?

Incontinence can sometimes be hereditary — but not in a way that’s easy to predict or diagnose.

Genetics can influence things like the amount of muscle you’re born with or the thickness of your urethra — both of which play a role in how well your bladder stays closed between trips to the toilet. However, these inherited traits are difficult to measure or confirm clinically, which means we often look at the bigger picture when assessing incontinence.

That said, just because your mum, aunt, or sister experienced incontinence doesn’t mean you definitely will too. It simply means it’s something to be mindful of, especially during life stages like pregnancy, postpartum, menopause, or with certain medical conditions.

The good news? Early awareness and working with a pelvic physiotherapist proactively can reduce your risk or manage symptoms before they escalate.

What other factors cause urinary incontinence?

Urethral or bladder prolapse: prolapse refers to movement of an organ from its normal resting position. Pregnancy, vaginal birth, genetics (related to connective tissue), respiratory conditions, chronic constipation are often common contributors to prolapse. If we think of the urethra like a straw with the urethral muscles around it, if the bladder on top leans to the side it can pull on the connection point between the two. This is known as funneling, where the bladder neck that joins onto the urethra stretches open, and some urine can get in. Now we know from my previous blog that this reflex can cause the bladder to contract contributing to urgency, but it can also stretch the muscles slightly apart making them weaker. The weaker the muscles, the more likely someone is to leak.

Vascular support: again explained in my previous blog, estrogen helps to improve vascular support to the urethra which contributes to <5% of its resting closure. This means it helps the urethral muscles to keep the urethra closed. Often not contributing to leakage by itself, it can just be the final straw that causes someone to develop leakage with urgency often related to menopause/post partum.

Other Blogs in the Bladder Series

Deep dive into education written by our pelvic physiotherapist, Rani, all about the bladder – including symptoms, treatment & understanding the range of associated conditions.