Pediatric kidney stone disease on the rise
Even in medicine, first impressions don't always reveal the truth. A usually very healthy teenager had gone to a local clinic complaining of pain and burning with urination - symptoms typical of an uncomplicated, "run-of-the-mill" urinary tract infection.
The patient was examined, treated, and sent home and seemed to feel better after her first 24 hours of oral antibiotics. Unfortunately, on the following day her symptoms returned with a vengeance.
In addition to burning, the high school student was now experiencing significant right pelvic and mild right lower back pain. An in-office urinalysis showed microscopic blood in the urine, and my colleague's careful history-taking unearthed a story of past kidney stones in the girl's mother.
Family history is important when evaluating these urinary symptoms, notes Dr. Charles P. McKay, in the journal Pediatrics in Review, since 20 to 50 percent of pediatric kidney stone patients have a positive family history of stones.
In fact, later that day, radiologic imaging studies did locate a calcified stone at the lower end of the girl's right ureter, the tube that carries urine from the kidney to the bladder. This kidney stone was large enough to obstruct the normal flow of urine, causing backup and moderate enlargement of the entire ureter as well as of the right kidney.
The teen was seen by urology and offered several options for kidney stone intervention or simple observation. She chose to wait for the stone to pass on its own, and was started on medication to reduce her urinary calcium excretion.
The kidney stone thankfully passed within a few days, was sent to the lab for analysis, and found to be made up of calcium oxalate, a component in about 80 percent of both adult and pediatric renal stones.
According to University of Pennsylvania medical researchers Drs. Gregory Tasian and Lawrence Copelovitch, pediatric kidney stone disease is on the rise. In their article in The Journal of Urology, the kidney specialists report that over the last 25 years the incidence of kidney stones in children has increased by 6 to 10 percent per year and now affects 50 out of every 100,000 adolescents.
Ultrasound is the usual diagnostic imaging study of choice when looking for pediatric kidney stones. Non-contrast CT scanning is used if a stone is still highly suspected even after a negative ultrasound.
The recurrence rate of pediatric kidney stones is not currently well-understood; however, the journal authors note that up to 70 percent of children with stones have existing urine abnormalities that will increase the risk of stone formation.
So, it makes sense for experts to recommend further medical evaluation when a child experiences a first kidney stone. Chemical analysis of stone composition, basic blood work, and a 24-hour urine collection can be performed to identify any metabolic abnormalities or risk factors that can potentially be modified by dietary changes and/or medication.
Tasian and Copelovitch note that a recognized major risk factor for kidney stones is poor fluid intake with resulting low urine volumes. In addition, high sodium intake is shown to increase urinary calcium excretion, and fructose-containing drinks are also thought to be linked to an increase in stone risk.
Because of these possible dietary risk factors, kids with a history of calcium-based stones are advised to increase their water consumption and decrease sugary drinks and daily salt intake.
The Pennsylvania researchers also find that most cases of excessive urinary calcium excretion are not due to intake of dietary calcium, so limiting calcium is not recommended. Though it seems counterintuitive, low dietary calcium has actually been linked to an increased risk of kidney stones in adults.
The kidney specialists also caution that while low protein diets may decrease adult kidney stone formation, growing children, even those at risk of kidney stones, should still eat their recommended daily allowance of protein.
• Dr. Helen Minciotti is a mother of five and a pediatrician with a practice in Schaumburg. She formerly chaired the Department of Pediatrics at Northwest Community Hospital in Arlington Heights.