There are many reasons for frequent peeing at night...
1. Outflow obstruction - a narrowing of the urethra causing you to pee slowly, such as a stricture or BPH or PCa. Peeing too slowly causes Incomplete Voiding - you finish peeing before emptying your bladder (you pee for a set length of time, not until your bladder is empty). If you go back to bed with a half-full bladder, it fills up again sooner and you'll need another pee. In the case of BPH, alpha-blocker drugs such as Tamsulosin or Alfuzosin can help by relaxing the smooth muscle of the internal sphincter and prostate, increasing flow rate around 20%, but with increasing BPH, there comes a point where drugs alone can't do enough and surgery such as a TURP is required. (Alpha blockers won't help much in the case of strictures or narrowing by PCa.) Double voiding (waiting after first pee, and peeing again) can also help in early stages providing you aren't close to going into retention (unable to pee).
2. Unstable Bladder (Bladder Spasms). The bladder is a thick muscle lined bag. The pressure in the bladder is normally low, but when you pee, the sphincter muscle around the bladder neck relaxes and the rest of the bladder muscle contracts to generate bladder pressure and force the urine out. Unstable bladder is when the bladder muscle contracts before the bladder is full, generating a sense of urgency. This can happen if there is something in the bladder which causes bladder irritation. Different things irritate different peoples' bladders, but typical ones are caffeine, alcohol, fizzy drinks, acidic drinks, concentrated urine (dehydration).
3. Unstable Bladder can also be caused by outflow obstruction, where peeing rate is too slow and bladder isn't being emptied.
4. Unstable Bladder can also be caused by inappropriate bladder training. People who have any lower urinary tract symptoms (incontinence, urgency, etc) often get into the habit of using the toilet whenever they get the opportunity. This trains the bladder to expect to not to fill up, so it starts generating bladder spasms when only partially full. Bladder retraining (learning how to retrain your bladder to fill up) can help with this. You can't do bladder retraining during the night (it would stop you sleeping), but bladder retraining you do during the day will improve night time too. Drugs like Solifenacin can help sometimes, but may also result in incomplete voiding.
5. Enlarged prostate, BPH or PCa - a large prostate will generate a significant dent in the bottom of the bladder. This has two effects, it reduces bladder capacity so it will fill up sooner, and it also stretches the base of the bladder, the area called the Trigone where the stretch receptors are which generate the sense of a full bladder, so you may get a sense you need to pee before the bladder is really full.
6. Drinking a lot in the hours before going to bed.
7. Odema. Fluid collected in the lower limbs during the day will typically drain back when you lay down, resulting in excessive water entering the blood stream at night and needing to be excreted.
8. Taking diuretic tablets too late in the day. This will cause your kidneys to still be excreting excess water overnight.
9. Anti-diuretic hormone not working. We release anti-diuretic hormone overnight to restrict the amount of water the kidneys excrete, so we can get a night's sleep without interruption to pee. As we get older, this mechanism can stop working so well. It is possible to be prescribed anti-diuretic hormone to take at bed time, but this comes with risks of high blood pressure and strokes overnight, and a requirement to manage your evening fluid intake very carefully, so it's not often used.
10. Bladder muscle not working. As mentioned earlier, to pee you need to both relax your internal urinary sphincter and to contract the rest of your bladder muscle. If the bladder muscle doesn't contract, you'll pee too slowly to empty your bladder before you stop peeing (another cause of Incomplete Voiding). Bladders usually hold around 500ml, but they are stretchy and can go over a litre. The bladder muscle will no longer work past about 1 litre, and can't force the urine out. If you routinely stretch your bladder, the muscle becomes permanently damaged and won't work even at normal capacities anymore. This can happen with long distance lorry drivers, and some people with phobias about using public or other peoples' toilets which causes them to wait a long time before peeing. It can also happen due to nerve damage.
That's probably not a complete list, but it's off the top of my head at the moment, with the more common causes first.
As you can see, there are a large number of causes and they have different solutions, so it is necessary to identify exactly why you are peeing frequently at night in order to come up with the right fix. A GP might just try things like Tamsulosin and/or Solifenacin to see if they work, but a urology department might do a proper urodynamics test to much better understand the cause, and ideally this would be done before considering any surgical procedure to tackle the problem.
Edited by member 02 Nov 2021 at 08:43
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