Summary

Kidney stones (nephrolithiasis) affect 10-15% of the population over a lifetime. Calcium oxalate stones are most common (70-80%). Presentation is typically severe, colicky loin-to-groin pain with haematuria. CT KUB (non-contrast) is the gold standard investigation. Most small stones (<5mm) pass spontaneously with conservative management. Larger stones or complications require intervention (shockwave lithotripsy, ureteroscopy, or PCNL). An infected obstructed kidney is a urological emergency requiring immediate decompression (nephrostomy/stent) and antibiotics.

Key Facts

• Lifetime Risk: 10-15% (recurrence 50% at 5 years)
• Stone Types: Calcium oxalate (70-80%), Uric acid (10%), Struvite (10%), Cystine (1%)
• Classic Pain: Loin to groin, colicky, severe ("worst pain ever")
• Diagnosis: CT KUB (non-contrast) - 98% sensitivity
• Management: Most <5mm pass; >10mm usually require intervention
• EMERGENCY: Fever + stone = infected obstruction = immediate drainage

Clinical Pearls

"Fever + Stone = EMERGENCY": An infected obstructed kidney can rapidly lead to sepsis and death. These patients need emergency decompression (nephrostomy or stent), not just antibiotics.

"Pain Severity ≠ Stone Size": A 3mm stone can cause excruciating pain while a staghorn calculus may be painless. Pain relates to ureteric distension, not stone size.

"Tamsulosin Helps Expulsion": Medical expulsive therapy with tamsulosin increases spontaneous passage rates for distal ureteric stones 5-10mm.

"Stone Analysis is Gold": Every first-time stone should be analysed. Composition guides dietary and medical prevention strategies.

Why This Matters Clinically

Renal colic is one of the most common presentations to ED. Distinguishing uncomplicated colic (manageable conservatively) from infected obstruction (emergency) is critical.

General

• Patient in severe pain, writhing, unable to settle
• Fever (suggests infection)
• Signs of dehydration

Abdominal Examination

• Renal angle tenderness
• May be normal between pain waves
• Usually soft abdomen (vs peritonitis = rigid)

Differential Diagnosis

Passage Rates by Size

Recurrence

• 50% recurrence at 5 years
• 75% recurrence at 10 years (without prevention)
• Metabolic workup and prevention can reduce by 50%

Prevention Strategies

Key Guidelines

1. NICE NG118: Renal and Ureteric Stones (2019)
2. EAU Guidelines on Urolithiasis (2024)
3. AUA/Endourological Society Guideline on Stones

Key Evidence

Medical Expulsive Therapy (SUSPEND Trial, 2015)

• RCT: No benefit for tamsulosin in stones <10mm
• But subsequent meta-analyses suggest benefit for 5-10mm distal stones

Fluid Intake

• Increased fluid intake reduces recurrence by 50%
• Target urine output >2L/day

What Are Kidney Stones?

Kidney stones are hard mineral deposits that form in your kidneys when your urine becomes concentrated. They can travel down the tube connecting your kidney to your bladder (ureter), causing severe pain.

What Are the Symptoms?

• Severe pain in your back or side that may move to your lower abdomen and groin
• Pain that comes in waves and fluctuates in intensity
• Blood in your urine (pink, red, or brown)
• Nausea and vomiting
• Needing to urinate frequently

How Are They Treated?

Small stones (<5mm):

• Often pass on their own with plenty of fluids and painkillers
• Medication (tamsulosin) may help the stone pass

Larger stones:

• May need procedures to break up or remove the stone
• Shockwave lithotripsy (sound waves break up the stone)
• Ureteroscopy (camera and laser to break up stone)

When to Seek Emergency Care

Call 999 or go to A&E if you have:

• Fever with kidney stone pain (suggests infection)
• Unable to pass urine
• Uncontrollable pain
• Confusion or feeling very unwell

Preventing Future Stones

• Drink plenty of water (aim for pale yellow urine)
• Reduce salt intake
• Moderate protein intake
• Keep any stones for analysis