Kidney Stones

Overview

• Also known as:
  • Renal calculi
  • Urolithiasis
  • Nephrolithiasis
• Form in the renal pelvis where urine collects.
• Can be asymptomatic until they irritate or get stuck in the ureters.
• Commonly stuck at the vesico-ureteric junction (junction between ureter and bladder).

Complications

• Obstruction:
  • Can lead to acute kidney injury due to back pressure.
• Infection:
  • Obstructive pyelonephritis (kidney infection caused by obstruction).

Types of Kidney Stones

1. Calcium-based stones (80% of cases):
   • Key risk factors: hypercalcemia and low urine output.
   • Types of calcium stones:
     • Calcium oxalate (more common)
     • Calcium phosphate
2. Other types:
   • Uric acid stones (radiolucent; not visible on X-rays).
   • Struvite stones (associated with infection; produce ammonia).
   • Cystine stones (associated with cystinuria).
3. Staghorn calculus:
   • Stone shapes like antlers in renal pelvis; often seen with struvite stones.

Presentation

• Asymptomatic:
  • Many stones never cause issues.
• Renal colic:
  • Unilateral loin to groin pain, often excruciating.
  • May experience hematuria, nausea, vomiting, and reduced urine output.

Investigations

• Urine dipstick test:
  • Shows hematuria; may not exclude kidney stones.
• Blood tests:
  • Check for signs of infection and kidney function (serum calcium).
• Imaging:
  • Abdominal X-ray shows calcium stones (not uric acid).
  • CT KUB (non-contrast CT kidneys, ureters, bladder) is the investigation of choice.
  • Ultrasound as an alternative, particularly in pregnant women.

Management

• Pain Management:
  • NSAIDs (e.g., diclofenac) are most effective.
  • IV paracetamol as an alternative.
  • Antiemetics for nausea (metoclopramide, procloperazine).
• Watchful waiting:
  • Stones < 5mm are likely to pass on their own (50-80% chance).
  • Stones 5-10mm may also be monitored based on individual factors.
• Tamulosin:
  • An alpha blocker to aid passage of stones.

Surgical Options

1. Extracorporeal Shockwave Lithotripsy (ESWL):
   • Uses shock waves to break stones into smaller parts.
2. Uretoscopy and Laser Lithotripsy:
   • Camera and laser to break stones.
3. Percutaneous Nephrolithotomy:
   • Surgical removal via a small incision in the back.
4. Open Surgery:
   • Rarely used, reserved for complex cases.

Recurrent Kidney Stones

• Predisposition to further episodes.
• Recommendations for prevention:
  • Increase fluid intake to 2.5-3 liters/day.
  • Add lemon juice to water (citric acid helps reduce stone formation).
  • Avoid carbonated drinks (cola contains phosphoric acid).
  • Reduce dietary salt intake < 6 grams/day.
  • Maintain normal calcium intake.
  • For calcium stones, limit intake of oxalate-rich foods (e.g., spinach, nuts).
  • For uric acid stones, limit purine-rich foods (e.g., liver, sardines).
• Medications to reduce recurrence:
  • Potassium citrate (for calcium oxalate stones).
  • Thiazide diuretics (e.g., indapamide).

Conclusion

• Importance of lifestyle changes and adequate hydration in prevention.
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