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Urinary Stones: Important Points for Exams

1. Types of Urinary Stones
1. Calcium Oxalate : most common type
• Radiopaque.
• Caused by hypercalciuria, hyperoxaluria.
2. Calcium Phosphate
• Radiopaque.
• Seen in alkaline urine.
3. Struvite → Magnesium Ammonium Phosphate
• Radiopaque.
• Associated with urease-producing bacteria eg Proteus, Klebsiella
• Forms staghorn calculi.
4. Uric Acid
• Radiolucent.
• Occurs in acidic urine.
• Associated with gout and high purine diet.
5. Cystine
• Radiolucent or faintly radiopaque.
• Seen in cystinuria → autosomal recessive disorder

2. Risk Factors
1. Metabolic
• Hypercalciuria.
• Hyperuricosuria.
• Hyperoxaluria.
• Hypocitraturia.
2. Dietary
• High salt and animal protein intake.
• Low water intake.
3. Infections
• Urease-positive bacteria form struvite stones
4. Genetic
• Cystinuria.
5. Anatomic Abnormalities
• Horseshoe kidney.
• Medullary sponge kidney.

3. Clinical Features
1. Symptoms
• Flank pain radiating to groin → renal colic
• Hematuria → microscopic or gross
• Dysuria and urinary urgency → if stone is in the lower tract
• Fever → if infection is present
2. Complications
• Obstruction.
• Infection : pyelonephritis, urosepsis
• Renal damage.

4. Diagnosis
1. Imaging
• Non contrast CT KUB:Gold standard for detecting stones.
• Ultrasound: Preferred in pregnancy.
• X-ray KUB: Useful for radiopaque stones like calcium and struvite
2. Urine Analysis
• Hematuria.
• Crystals : calcium oxalate, uric acid
• pH:
• Acidic: Uric acid and cystine stones.
• Alkaline: Struvite stones.
3. Metabolic Evaluation
• 24-hour urine test for calcium, oxalate, and citrate.

5. Treatment
1. Acute Management
• Pain control: NSAIDs e.g. diclofenac or opioids for severe pain.
• Hydration: High fluid intake to promote stone passage.
• Medical Expulsion Therapy: Alpha-blockers e.g., tamsulosin.
• Intervention:
• Shockwave Lithotripsy : For stones less than cm.
• Ureteroscopy : For mid or distal ureter stones.
• Percutaneous Nephrolithotomy : For large or staghorn stones.
2. Prevention
• Hydration: Maintain more than 2.5 L/day urine output.
• Dietary Modifications:
• Reduce sodium and oxalate intake.
• Increase citrate intake from fruits like lemons/oranges
• Medications:
• Thiazide diuretics which reduce calcium excretion
🎯Don’t give loop diuretics like furosemide which looses calcium in urine.
• Potassium citrate /bicarbonate for alkalinization of urine

6. Key Points for Exams
1. Most common stone: Calcium oxalate.
2. Radiolucent stones: Uric acid, cystine.
3. Urease-producing bacteria: Struvite stones.
4. Acidic pH favors: Uric acid and cystine stones.
5. Gold standard investigation: non contrast CT KUB
6. Staghorn calculi: Typically struvite stones.
7. Treatment for uric acid stones: Urine alkalinization with potassium citrate.

Focus on types, clinical features, diagnostics, and treatment approaches to ace this topic!