Kidney Stones (Nephrolithiasis)

Types of Kidney Stones

• Calcium Oxalate (70–80%)

  • Most common, often linked to hypercalciuria, hyperoxaluria

• Struvite (10–15%)

  • Associated with urease-producing bacteria (e.g. Proteus, Klebsiella); risk of infected obstruction

• Uric Acid (5–10%)

  • Radiolucent on plain X-ray, linked to acidic urine & high purine intake

• Cystine (<2%)

  • Rare, due to cystinuria, often starts in childhood

When to Refer to Urology

Urgent (Immediate Surgical Assessment)

• Sepsis (fever, tachycardia, hypotension)

• Uncontrollable pain despite maximal analgesia

• Significant renal failure (rising creatinine, AKI)

• Single kidney or pre-existing renal disease with obstructing stone

• Stone >7 mm (unlikely to pass spontaneously)

Non-Urgent (Long-Term Follow-Up)

• Failure to pass stone within 3 weeks

• Persistent haematuria after stone passage

• Recurrent or severe pain despite conservative management

Investigations

Initial Workup

• Bloods:

  • UEC, CMP for renal function, electrolytes, calcium, uric acid

  • FBC, CRP if infection suspected

• Urine Tests:

  • Urinalysis, urine MCS (check haematuria, infection)

  • Urine pH (acidic → uric acid stone, alkaline → struvite)

  • Stone analysis if a stone is passed/retrieved

• Imaging:

  • CT KUB (non-contrast): Gold standard for diagnosis

  • XR KUB: Follows known radio-opaque stones

  • Renal ultrasound: Option if pregnant or younger patients <50 with mild suspicion

• Follow-Up:

  • Repeat CT KUB in ~4 weeks unless stone is retrieved

  • 24-hour urine collection for recurrent stones or metabolic abnormalities

Management

Short-Term (Acute Pain Relief & Stone Passage)

• NSAIDs first-line: e.g. ibuprofen 400 mg PO TDS

• If vomiting or severe pain: indomethacin 100 mg suppository or opioids (morphine) if needed

• Antiemetics: e.g. metoclopramide 10 mg IV/IM

• Alpha-Blocker: Tamsulosin 400 mcg daily (helps distal ureteric stone passage; no immediate pain relief)

• Hydration: Encourage oral fluids; IV bolus fluids for forced diuresis are no longer recommended (may worsen renal colic)

Long-Term (Prevention & Monitoring)

• Post-Discharge Analgesia: Ibuprofen 400 mg TDS PRN, paracetamol 1 g QID PRN, tamsulosin 400 mcg daily, metoclopramide 10 mg TDS PRN

• Monitoring: Strain urine for stone retrieval and analysis; repeat imaging if stone not retrieved; return if fever or worsening pain

Lifestyle & Prevention

• Hydration: Aim for urine output >2.5 L/day (clear/pale urine)

• Dietary Modifications:

  • Low oxalate (limit spinach, nuts, chocolate, beans)

  • Moderate protein to reduce acidity (limit red meats)

  • Lower sodium to decrease urinary calcium excretion

  • Normal dietary calcium (avoid supplements) is protective

• Weight Management: Obesity increases risk

• Dietitian Referral for personalised advice

Pharmacological Prevention (If Lifestyle Alone Fails)

• Thiazide Diuretics: Decrease urinary calcium excretion (for calcium stones)

• Allopurinol: For recurrent uric acid stones

• Potassium Citrate: Alkalinises urine, preventing uric acid or cystine stone formation

Notes

• NSAIDs reduce ureteric inflammation and help analgesia; first-line for renal colic.

• Tamsulosin aids passage of distal ureteric stones (>5 mm), but does not offer immediate pain relief.

• Struvite Stones: Associated with recurrent UTIs; ensure long-term follow-up.

• Stone Size:

  • ≤5 mm → ~80% chance of spontaneous passage

  • 7 mm → often needs urological intervention.

• Forced Diuresis is no longer recommended due to risk of exacerbating renal colic.