Understanding bladder basics: how the bladder works and how it signals fullness.
In this series we’re going to be talking all things bladder. What normal bladder function should look like, common symptoms of dysfunction we see, why they happen, and different treatment strategies. It might be the nerd in me, but I really think it’s good to understand the function of the body and why things happen, so that you know why we do certain treatments. So let’s start at the beginning!
What is the bladder?
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The bladder is an organ which transports urine from the kidneys down and out of the body. We have the ureters running from the kidneys into the back side of the bladder, and then one urethra running from the base of the bladder to the outside world. In women this exits just above the vaginal opening (yes, we do not wee from inside the vagina because I know some people will be surprised by this), and then for men this runs through the penis.
What does the bladder do?
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The bladder has 2 main functions: storage of urine and voiding urine (weeing).
99% of the time, our bladder is filling, and then a few times a day, it empties.
There are no specific numbers that you must be going to the toilet each day, but we know the average is 5-8 throughout the day, and 0-1 overnight. If you go less or more frequently, but you have no concerns/symptoms of it, we aren’t overly worried.
What makes up the bladder?
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The bladder itself is made up of a few different layers which is important to understand how it functions. The main parts I, as a pelvic physiotherapist, like people to be aware of is:
- Detrusor: the outer muscular layer of the bladder.
- The Submucosa/lamina propria: middle layer containing the nerve fibers (and bloodvessels/connective tissue).
- The Urothelium: separates the nerves from urine.
- The space inside the bladder where urine is.
How does the bladder work?
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The muscle lining of the bladder is one we as physio’s tend to focus on (muscles are our favourite). The muscle mostly stays in a relaxed state which stretches as the bladder fills. The bladder and kidneys are organs that function all times of day, they never get a rest, so the bladder is consistently getting larger and having more stretch.
The middle nerve layer is the one that tells the body mainly what is going on, so as the detrusor layer stretches, this triggers the nerves in the mid layer to relay information to the brain regarding how much of a stretch is present (i.e. how full your bladder currently is).
At all stages, our brain is working behind the scenes to keep us functioning to do everything else we have to, and prioritizes well. If you’re busy on a zoom work call, mid run, or it’s just not a convenient time to go, the brain can often muffle or fully cover these ‘need to urinate’ signals. A great example of the brains ability to cover something up is our nose. We actually see our nose all times of day, but our brain deems it not important so it blocks it out for us (try looking at your nose now).
When we then decide to urinate, we should be able to comfortably walk to the toilet, and when sitting and ready to go, be able to urinate relatively quickly and easily. This is where the detrusor layer comes back into play. It is the muscular detrusor layer that contracts to squeeze the urine out of the bladder. This is where we start to get into the common symptoms of dysfunction that we’re going to be going over in upcoming blogs.
When is the bladder full?
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The average bladder can hold at least 450mL – and at this stage of ‘full’ an urgent desire to void your bladder would be considered very normal!
Most people will have an awareness of something being in the bladder around 80-120mLs, but not actually have the urge to urinate due to the very small stretch on the bladder. It isn’t until the bladder gets around 150-250mLs that the stretch is high enough to trigger an actual urge to urinate. The urge around this stage should be mild-moderate. The more the bladder fills, the stronger the urge should get.
Common symptoms of bladder dysfunction?
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Some common symptoms that might indicate towards bladder dysfunction include:
- The need to urinate often with only small amounts of urine present,
- Strong, sudden urges to urinate without the ability to calmly walk to the toilet,
- Feeling incomplete emptying, and/or the need to strain to empty,
- Urinary leakage in any form, including with a sneeze/cough, on walking to the toilet or without even feeling it leak.
These are common symptoms we see in clinic, that we can help with. I’m going to go into more detail regarding the causes of these, so you can understand more of the treatment options (and you’ll understand why I had to give the boring anatomy lesson above).
References
Reference: To be confirmed.
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.
Urinary Incontinence: What causes bladder leakage?
What causes bladder urgency?
