My 3-year-old daughter is taking Bactrim as a prophylactic because her urine backs up into both kidneys when she urinates. They called it "Reflux". I was told that some children outgrow this condition, but if she doesn't surgery is required. We have to wait until she is 6 or 7 to see if this problem can solve itself. In the meantime I'm concerned about the overuse of antibiotics. I would rather have her on antibiotics than go through surgery but I'm also worried about her resistance to other infections. Are there any other options? Can her bladder be strengthened through some sort of exercise?

Dr. Greene: The body uses an intricate filtration system to keep our bloodstreams clean, and with just the right pH and concentrations of sodium, potassium and other substances. This incredible filtration system begins operating as early as the 9th week of fetal life, and silently continues year by year. When everything is working well, we pay very little attention, but when this system fails, we understand just how important it is.

Normally the kidneys manufacture urine. The urine is transported through two tubes called ureters, and stored in the bladder, a muscular sac a bit like a thick-walled water balloon. The urine is excreted through an exit tube called the urethra when you urinate. When the bladder muscle contracts, the entrances from the ureters into the bladder are normally squeezed shut, forcing the urine to go one-way, out the urethra. In some children, however, the connection where the ureters enter the bladder muscle allows urine to go back up toward the kidneys as well as down through the urethra when the bladder muscle is contracted. This is called vesicoureteral reflux.

There are three problems associated with vesicoureteral reflux. First, when the bladder contracts, causing urine to be forced upwards, the urine puts pressure on the kidneys which they are not intended to experience. This can produce scarring of the kidneys. The kidneys and ureters can also become dilated from the back-up, leading to poor function. The second problem is that the urine that squirts backwards quickly returns to the bladder. We depend on the bladder to completely expel the urine in order to get rid of the small amounts of bacteria that can enter the bladder (especially in girls, who have short, straight urethras connecting the bladder to the outside world). Effective bladder emptying is a major defense against infection. Kids with reflux get bladder infections more easily. The third problem is that the urine that goes backward can carry the infection found in the bladder past this line of defense, up to the kidney, resulting in serious infections and possible kidney damage.

Thankfully, the great majority of children with reflux outgrow this over the course of several years. Reflux is divided into grades I, II, III, IV, and V. In children with grades I and II, 80% will resolve spontaneously by school age. Spontaneous resolution is progressively less common in grades III and IV (only about 10% of grade IV involving sides), and rare in grade V. Progress can be followed by using ultrasounds and x-rays (particularly one called a voiding cystourethrogram, or VCUG, which takes pictures of the bladder contracting and the urine exiting).

In the meantime, using small doses of prophylactic antibiotics, such as Bactrim, will actually improve your child's defenses against infections and will make her stronger rather than weaker. Her urine should be tested periodically to detect any asymptomatic infections.

In the event that the condition does not improve, surgery would probably be necessary. Unfortunately, there are no exercises that can help correct this problem, because it is not a condition related to muscle tone, but rather the alignment of the ureters.