Some children have some difficulty in passing at occasionally. The most common cause is urine infection, where the child has pain in passing urine along with fever. It is usually because of a tight foreskin in boys or poor toilet habit in girls. But some children have to be investigated because they may problems of the kidney, ureters or bladder, which if ignored can cause life threatening illness.
Some children have swelling of one kidney usually detected before birth. These children need to be investigated to check if the kidney is blocking the flow of urine. Some children may pass urine with great difficulty. This may be because of there is a problem with urethra (urine passage from the bladder). If it is not treated promptly some children may develop long term kidney problems.