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Infection is the most common cause of frequent urge to urinate.
He has been tested for it.
Diabetes can also occur in this age. I think blood tests did not find any such.
Prostate problem is unlikely here but there can be anatomical changes in the urinary tract.
Stone in the bladder can cause an irritation.
An ultrasound examination of bladder, kidney can be taken.Allergy
to soap, pinworm can cause an irritation.
Sometimes, no cause can be detected. Stress can be the factor of it. Over times it goes away.
Voiding dysfunction can occur too in this age group. The child may not completely pass urine when he goes to toilet. In that case proper toilet training
will be required.
I hope this information will be helpful.
If you have any query, please feel free to ask.
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Wish his healthy life.