Renal Calculus

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)
    • 5% uric acid
    • Others: Magnesium ammonium phosphate (struvite), cystine
  • Struvite: Associated with infections caused by urea-splitting organisms (e.g., Pseudomonas, Proteus, Klebsiella) along with an alkalotic urine
  • 90% of urinary calculi are radiopaque

Etiology

• 6–12% lifetime risk in the general population
• Twice as common in patients with family hx
• Male:Female 1.3–1.6:1
• Peak incidence between 40–60 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

• Rare in children
• 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%)
  • Urologic abnormalities (20%)
  • Infection (15%)
  • Immobilization syndrome (5%)