Urolithiasis in children
As the prevalence of stone disease has grown, so has the importance of understanding disease process, diagnosis, and management.
Diagnosis, treatment, and prevention
Although many children and adolescents with urolithiasis present with abdominal or colicky flank pain, similar to adults, many children may have nonspecific symptoms, such as generalized abdominal pain, nausea, vomiting, or nonspecific findings consistent with urinary tract infection. Many children will have gross hematuria as initial presenting sign of urolithiasis.
Treatment of children with renal stones is actually similar to that of adults. Many children will pass similarly sized stones as adults. Fifty percent of children will pass stones 4 mm to 5 mm in size regardless of the child’s size. Increased hydration and pain management with either nonsteroidal anti-inflammatory drugs (NSAIDs) or, rarely, narcotics help children manage their symptoms while passing a stone. Many children can be treated as outpatients and do not require hospital admission on presentation or when symptoms are controllable.
Alpha-adrenergic blockade (tamsulosin) has been used in children as well. The use of stone expulsion treatment particularly to facilitate passage of distal ureteral stones appears to have similar success in children as in adults and the medications are well tolerated by children, although current studies are limited.
Long-term prevention includes increased fluid intake, particularly water, up to 2 liters per day to 2.5 L/d in adolescents, or more in cystine stone formers. Improved fluid intake and salt and sugary drink limitations are critical for prevention of recurrence of stones in most children and adolescents, but are difficult to achieve, just as these improvements are similarly difficult to achieve in adults.
Specific treatments depend, if possible, on obtaining urine and serum testing for causative factors in stone formation. This is somewhat difficult in the non–toilet-trained child, where obtaining a 24-hour urine collection would require an indwelling catheter and bag collection. Spot urine tests for causative factors have been performed and can be helpful in determining specific metabolic abnormalities that the child may have and may help direct preventive treatment.
Decreasing high animal protein intake and sodium intake are important in any dietary recommendations for stone prevention, as is appropriate intake of potassium, calcium, and magnesium, which are protective against oxalate composite stone formation.
Potassium citrate (2-4 mEq/kg/d) is also a mainstay in preventive treatment in children at risk for stone formation because of underlying metabolic abnormalities, but it is not very palatable and may be hard to give to children for the 2 to 3 times a day that may be needed to improve urinary citrate concentrations.2,5 Potassium citrate is found in several clear lemon-lime soft drinks (such as Sprite, 7UP or Mist Twst [formerly Sierra Mist]) that are generally more palatable to children, may be less costly than prescription potassium citrate, are available in sugar-free forms, and have the additional advantage of increasing fluid intake while improving urinary citrate levels.
Radiologic evaluation for urolithiasis in children is predicated on ALARA (as low as reasonably achievable) techniques. Adult patients are generally evaluated with high-radiation testing such as computer tomography for diagnosis, treatment, and surveillance. These high-radiation techniques are rarely needed in children unless there is some uncertainty as to diagnosis or conflicting findings on low-radiation techniques that are generally used.
It is easy to obtain an abdominal flat plate (KUB [kidneys, ureter, bladder]) and ultrasound imaging of the kidneys and bladder, as these tests will find most stones because the majority of stones in children are radiopaque. Furthermore, most large stones in the kidney or ureter near the bladder that may need interventional treatment will be found on these studies.5 Smaller stones, as mentioned, tend to pass spontaneously and may be inferred if not directly seen by the presence of hydronephrosis or hydroureteronephrosis in ultrasonography (Figures 1 and 2).