DESCRIPTION

• Urolithiasis is the occurrence of calculi (stones) within the urinary tract, including the kidney, ureter, or bladder.
• Stones may be composed of calcium oxalate, calcium phosphate, uric acid, cystine, magnesium ammonium phosphate, xanthine, indinavir, or triamterene.

EPIDEMIOLOGY

• The incidence of stones in children of both sexes has increased over the last 25 years. In the adolescent population, the prevalence is about 50 per 100,000.
• In children, 50% have a metabolic syndrome associated with urolithiasis.
• 75% have a metabolic predisposition to forming stones.

RISK FACTORS

• Poor fluid intake
• Immobility
• Urinary tract obstruction
• Urinary tract infection (UTI) (associated with Proteus mirabilis or Escherichia coli)
• Bladder augmentation
• Dumping syndrome

PATHOPHYSIOLOGY

• The urine contains multiple solutes; some help prevent crystallization and some contribute to crystal formation.
• The likelihood of a solute crystalizing varies with the pH of the urine (e.g., uric acid crystal formation is more likely at lower pH).
• When enough crystals form in the urine and urine flow out of the kidney is slow or obstructed
• Crystals then coalesce into a small nidus on which more crystals will form. This process then leads to stone formation.

COMMONLY ASSOCIATED CONDITIONS

Children who present with urolithiasis age <6 years are more likely to develop hypertension (HTN) and diabetes mellitus (DM) later in life.