My child goes to the toilet a lot in the day: is this why they wet the bed at night?

Some parents notice that their child pays lots of visits to the bathroom during the day and wonder if this may be why they wet the bed at night.

Most children would be expected to toilet 4-7 times a day, so anything more than this may be a cause for concern.

If a child is toileting 8 times or more a day there may be several reasons for this:

• A small bladder capacity for age
• Having a twitchy (overactive bladder)

Identifying the reasons for excessive daytime toileting and addressing them may help with bedwetting, particularly if the child has a small bladder capacity and/or an overactive bladder. Generally, however, bedwetting is the result of failure to rouse to the signal from the bladder that it is full and needs emptying. Sometimes a child produces too much urine at night due to low levels of anti-diuretic hormone (ADH) and this can aggravate bedwetting, particularly if the bladder capacity is small to start with.

So how can excessive daytime toileting be addressed to help with night time bedwetting?

Recommended daily fluid intake for children

Children need to be well-hydrated to maintain healthy, active bodies. Drinking water regularly throughout the day can also help to stretch a small bladder.

The rule of thumb is a child’s daily consumption of fluid (preferably water) is 55ml/kg of body weight. So, if your child weighs 25kg they should be drinking around 1.4L of fluid a day, or, 5 -6 glasses of 250mls each. If they are drinking significantly more it may pay to have a doctor’s check-up to rule out conditions like diabetes mellitus. If they are drinking significantly less it would pay to increase their fluid intake as this will help stretch the bladder and increase its capacity so it can hold more at night time.

Drinks should be spread out over the day rather than being concentrated at the end of the day, before bed.

What is the normal bladder capacity of a child?

The expected bladder capacity (EBC) for children is worked based on the following formula:

EBP= (age of child x 30) + 30 mls

So, if your child is 7 years old their expected bladder capacity is (7*30)+30mls, or, 240mls.

Measuring daytime urine production

If you want to estimate your child’s bladder capacity you should measure and record how much urine they pass during the day over a period of 4 days (during weekends or holidays is the easiest time to do this), excluding their first morning wee. You can measure this by getting your child to pee into a measuring container or a bowl/potty which can then be poured into a measuring container. The largest amount of urine at any single visit during the 4 days is taken as the child’s bladder capacity.

Where a child’s bladder capacity is less than 65% of the expected bladder capacity then the child is said to have a small bladder. So, in the example of a 7-year-old, if the bladder capacity is less than 156ml the child is suffering from a small bladder.

As already indicated, making sure your child’s daily fluid consumption is consistently adequate can help improve bladder capacity in under-capacity children.

Measuring night-time urine production

If you want to try and work out whether your child produces too much urine during the night (due to low levels of ADH) you need to measure their night time wetting activity.

To do this wake your child up several times during the night and ask them to pee into a measuring container and add up the volume of urine they pass during the night to the measured volume of their first morning wee.

Alternatively, if your child wears pull-ups during the night, measure the weight in grams of the dry pull-up before bedtime and the weight of the wet nappy in the morning. (Take the difference between the two weights and convert it to mls (1 gram=1 ml) and add the volume of the first morning wee in mls). For example, if the weight of the dry pull-up is 50gms and then in the morning the wet nappy weighs 320gms, the difference is 270gms or 270mls. And, if the first morning urine volume is 50mls, the total amount of urine produced during the night time is 320ml. 

In the case of a 7-year-old the expected bladder capacity is 240mls, so night time urine production of 320mls is far more than the expected bladder capacity. The rule of thumb is where the night time urine production is more than 130% of the expected bladder capacity then the child could suffer from low levels of ADH.

Low levels of ADH in conjunction with a small bladder capacity can benefit from adequate daily fluid intake to stretch the bladder, in conjunction with bedwetting alarm therapy. But where the child is unable to progress with these solutions, pharmacological treatments could be looked at for children over 7 years old.

Overactive Bladder

Sometimes children can suffer from an overactive or ‘twitchy’ bladder, which means the bladder voiding reflex is not constrained so the bladder automatically voids before it reaches capacity. This can often be seen during the day if a child must rush, busting, to go to the toilet, frequently.

It can also be caused by voiding postponement where the child delays toilet visits (usually where they go less than 4 times a day) because they are too busy at school or where they are at home and pre-occupied watching television or playing games. These symptoms are evidenced by ‘holding’ postures such as leg crossing, squatting or pressing the heels into the bottom area.

Where voiding postponement is the cause of the child’s urgent toilet activities, then ensuring they have regular, relaxed, timed toilet visits throughout the day, plus good fluid intake can help, reduce or eliminate the symptoms. Where a twitchy bladder is due to overactivity of the bladder these strategies may help, but, where there is no improvement in a child’s bedwetting, consideration may be given to pharmacological treatments (e.g. anticholinergics) for children over 7 years of age.

Conclusion

The causes of bedwetting may be due to multiple factors e.g. genetic, stress-related or physiological. However, where your child exhibits overactive (or underactive) daytime toileting symptoms then measuring their bladder capacity and treating the daytime symptoms first may help in the treatment of their bedwetting.

It is always recommended that you seek guidance from a physician or other qualified health practitioner where the symptoms of bedwetting remain intractable or protracted.

Have you tried our Bedwetting Questionnaire? Get answers specific to your child.