Renal Calculus

Basics

Description

  • Urinary tract stones which may cause obstruction
  • Intermittent distention of the renal pelvis of proximal ureter produces pain
  • Kidney stones:
    • Most common cause of renal colic
    • Stone composition:
      • 80%: Calcium stones (calcium oxalate > calcium phosphate)
      • 7% uric acid
      • 7% magnesium ammonium phosphate (struvite)
      • 1–3% cystine
    • Struvite: Associated with infections caused by urea-splitting organisms (eg, Proteus, Pseudomonas, Klebsiella) along with an alkalotic urine
    • 90% of urinary calculi are radiopaque

Etiology

  • 1–15% lifetime risk in the general population
  • Twice as common in patients with family hx
  • Male:female 1–2.4:1
  • Peak incidence between 40 and 60 yr old
  • Theories on stone formation:
    • Urinary supersaturation of solute followed by crystal precipitation
    • Decrease in the normal urinary proteins inhibiting crystal growth
    • Urinary stasis from a physical anomaly, catheter placement, neurogenic bladder, or the presence of a foreign body
  • Recurrence rate of 15% at 1 yr, 40% at 5 yr, 50% at 10 yr, and 75% at 20 yr
  • Associated with chronic kidney disease, hypertension, type 2 diabetes mellitus, metabolic syndrome, gout, gastric bypass procedures, short bowel syndrome, frequent UTIs, and an increased risk of coronary artery disease

Pediatric Considerations

  • Rare in children, but increasing in prevalence
  • When present, often is an indication of a metabolic or genetic disorder
  • 60% present with flank or abdominal pain though up to 30% only present with hematuria
  • Pediatric patients <16 yr comprise ∼7% of all cases of renal stones
  • 1:1 sex distribution
  • Causes of stone formation:
    • Metabolic abnormalities (50–95%)
    • Urologic abnormalities (20%)
    • Infection (15%)
    • Immobilization syndrome (5%)
  • Recurrence rate up 50% at 3 yr
  • All children affected should undergo a complete metabolic workup

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