Overview
Definition
The formation of solid crystal aggregations (calculi) in the kidneys or urinary tract.
Epidemiology
Lifetime prevalence ~10%. High recurrence rate. More common in men and in hot, arid climates.
Etiology & Risk Factors
- Calcium Oxalate (80%): Most common. Radio-opaque. Associated with hypercalciuria, hyperoxaluria (Crohn's, spinach), and low urine citrate.
- Uric Acid (10%): Radiolucent (invisible on plain X-ray). Associated with gout, high purine diet, and acidic urine.
- Struvite (10%): Magnesium ammonium phosphate. Caused by urease-producing bacteria (Proteus, Klebsiella) causing large 'staghorn' calculi in alkaline urine.
Clinical Symptoms
- Renal colic: Sudden, excruciating, severe unilateral flank pain that radiates to the groin or testicle/labia
- Patients cannot sit still (unlike peritonitis, where patients lie completely still)
- Nausea, vomiting
- Hematuria (gross or microscopic)
Clinical Approach
Diagnosis
- Non-contrast CT Abdomen/Pelvis (Gold Standard): Highly sensitive and specific for all stone types
- Urinalysis: Microscopic hematuria
- Ultrasound: Alternative for pregnant patients or children (shows hydronephrosis)
Management
- Stones < 5mm: Conservative management (IV hydration, NSAIDs/Ketorolac for pain, Tamsulosin to facilitate passage)
- Stones 5-10mm: Shock Wave Lithotripsy (SWL) or Ureteroscopy (URS) with basket extraction
- Stones > 10mm (or Struvite): Percutaneous Nephrolithotomy (PCNL)
Complications
- Hydronephrosis (dilation of the renal pelvis)
- Pyelonephritis (infected stone is a UROLOGIC EMERGENCY requiring urgent decompression via nephrostomy tube or ureteral stent)