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Polydipsia (drinking too much water) can certainly result in frequent urination. Metabolic causes can also make a person feel thirsty and need to drink all the time.
Q: My son is now six years old and is generally an active boy with a good appetite.
However, I am concerned about his frequent urination. Sometimes, after drinking water, he goes to relieve himself two to three times within an hour.
This problem has persisted since he was 18 months old.
Is this considered normal or would you suggest a medical review for him?
A: First, you need to evaluate if your son is drinking too much water.
Polydipsia (drinking too much water) can certainly result in frequent urination.
You can prepare a water intake and output diary for three days to assess this.
Buy a simple measuring jug to measure the amount of urine your son passes.
To get an idea of his intake of water, just estimate the number of cups of water that he drinks.
There are no special signs to look out for. Just chart the intake of water and output of urine. They should balance each other.
This diary will also show if your son is passing a lot of urine because he is drinking too much water.
Polydipsia can be psychogenic (mental) or metabolic (related to how the body produces energy and waste) in origin.
The former means the person is a compulsive water drinker who is obsessed with drinking too much water - in excess of 3 litres - every day.
Metabolic causes include diabetes mellitus (high blood sugar) and diabetes insipidus, a condition characterised by the excretion of large amounts of severely diluted urine, with reduction of fluid intake having no effect on the concentration of the urine.
These metabolic conditions make the person feel thirsty and need to drink all the time.
If your son is really suffering from polydipsia, he will need to have a proper metabolic evaluation done by a doctor.
Alternatively, your son may be suffering from frequent urination despite not drinking too much water, which occurs more commonly than polydipsia. The causes include urinary stones, urinary tract infection and idiopathic (without any known cause) overactive bladder.
A visit to the urologist will be helpful as the doctor can do a urine check and a simple bedside ultrasound scan to rule out any urinary stone and urinary tract infection.
The most likely cause for frequent urination is idiopathic overactive bladder.
Typically, the patient passes urine frequently (every hour), wakes up at night to urinate and the amount of urine is usually not much.
Overactive bladder can be treated with lifestyle changes, bladder training and medication.
Lifestyle changes include abstinence from carbonated drinks and cold drinks.
Bladder training involves gradual holding of the bladder for longer periods of time - at least 1 1/2 hours. Doing so will help to stretch the bladder muscles and increase the bladder capacity gradually.
Medication given includes anti-cholinergic drugs (inhibitors) such as detrusitol and vesicare.
Such drugs work by blocking signals sent by nerves that control contractions of the muscle in the wall of the bladder, so that this muscle relaxes. This reduces the urge to urinate.
The choice of treatment should be decided after a consultation and discussion with the doctor.
Dr Fong Yan Kit
Consultant urologist at Raffles UroRenal Centre at Raffles Hospital
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