Bladder size varies considerably from child to child. Much like height and weight vary among different children and families so does bladder size. The typical bladder size of a child should be equal to their age + 2 = # ounces. So a child 6 years old should have a bladder capacity = 6 + 2 = 8 ounces (240ml). Children with small bladders need to use the bathroom more often. This is true both day and night.
Studies have shown children with smaller bladders are more likely to wet at night. There is no easy way to measure the bladder size. The most accurate way is to place a tube (catheter) into the bladder and measure the amount it holds. It is painful to insert a catheter and kids do not tolerate it well. Since it is not usually possible to increase bladder size, this procedure should not be routinely performed.
Some doctors used to recommend holding urine for long periods of time during the day to stretch the bladder. This only caused confusion and promoted abnormal daytime potty habits because children would tighten their bottom muscles (sphincters) in order to avoid using the restroom. As a result, they would not relax long enough to let all of the pee out. A bladder that does not empty leads to other problems, including more bedwetting.
Furthermore, contrary to what was initially thought, the bladder does not usually stretch and get larger with holding. The holding exercises are no longer thought to be successful in correcting bedwetting and these practices may even be harmful.
Dr. Smith is board certified and he has authored or co-authored many articles, papers, chapters, and books in Urology and Pediatric Urology. His research has been presented throughout the world. Dr. Smith’s dedication to helping children with urologic problems inspired him to establish PottyMD.