Renal Stones (Urolithiasis)
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Urolithiasis affects 10-15% of the population. Stones cause symptoms when they obstruct the ureter, causing proximal dilation (hydronephrosis) and capsular stretch. The combination of Obstruction + Infection is a urological emergency necessitating urgent decompression.
Clinical Scenario: The Restless Patient
A 40-year-old man presents writhing in agony, unable to find a comfortable position. He complains of waves of severe left loin pain radiating to his scrotum. He has vomited twice.
Key Teaching Points
- **Diagnosis**: **Left Ureteric Colic**.
- **Behaviour**: Unlike peritonitis (patient lies still), renal colic patients move constantly.
- **Analgesia**: **PR Diclofenac** (NSAIDs) is more effective than morphine as it reduces glomerular filtration rate and ureteric spasm.
- **Emergency Check**: If he had a fever >38°C, this would be an **Obstructed Infected Kidney** requiring immediate nephrostomy.
Image Integration Plan
| Image Type | Source | Status |
|---|---|---|
| Management Algorithm | AI-generated | PENDING |
| CT KUB (Ureteric Stone) | Web Source | PENDING |
| X-Ray (Staghorn Calculus) | Web Source | PENDING |
| Diagram (Stone Types) | AI-generated | PENDING |
[!NOTE] Image Generation Status: Diagrams illustrating the sites of ureteric constriction are queued.
Stone Composition
| Type | Frequency | Radiopacity | Cause |
|---|---|---|---|
| Calcium Oxalate | 75% | Opaque | Dehydration, Hypercalciuria. |
| Calcium Phosphate | 10% | Opaque | Alkaline urine (RTA). |
| Uric Acid | 5-10% | Lucent (Invisible) | Acidic urine, Gout. |
| Struvite | 5-10% | Opaque | Infection (Proteus). Staghorn. |
| Cystine | 1% | Semi-opaque | Genetic (Cystinuria). |
- Prevalence: increasing (dietary factors).
- Sex: Male > Female (2:1).
- Age: Peak 30-50 years.
- Recurrence: 50% recur within 5-10 years.
- Supersaturation: Urine contains more solute than can stay in solution.
- Nucleation: Crystals form.
- Sites of Impaction:
- PUJ: Pelvi-ureteric junction.
- Pelvic Brim: Crossing iliac vessels.
- VUJ: Vesico-ureteric junction (Narrowest point).
- Abdomen: Soft (pain is retroperitoneal). Renal angle tenderness.
- Genitals: Testicular pain (referred) - exam usually normal.
- CT KUB (Non-Contrast):
- Gold Standard. Sensitivity 99%.
- Diagnoses stone size, location, and density (Hounsfield Units).
- Ultrasound:
- First line for Children and Pregnant women.
- Good for Hydronephrosis, poor for ureteric stones.
- Urinalysis: Blood +++.
- Bloods: Renal function (AKI?), CRP/WCC (Infection?), Calcium/Urate (Metabolic workup).
A. Emergency Decompression
Indication: Obstructed Infected Kidney (Fever/Sepsis + Hydronephrosis).
- Antibiotics alone cannot penetrate the obstructed system ("Pus under pressure").
- Treatment: Urgent Nephrostomy or Retrograde Stent.
- Definitive stone treatment is delayed until infection clears.
B. Conservative (MET)
- Medical Expulsive Therapy:
- Indication: Stones < 10mm (especially distal). Pain controlled. No infection.
- Tamsulosin (Alpha-blocker): Relaxes ureteric smooth muscle. Increases passage rate by ~30%.
- Analgesia: NSAIDs (Voltaren/Diclofenac) PR/IM.
- Review: If not passed in 4 weeks -> Surgery.
C. Elective Surgery
- ESWL (Extracorporeal Shockwave Lithotripsy):
- External machine focuses shockwaves. Outpatient.
- Best for: Renal/Proximal stones < 2cm.
- Contraindications: Pregnancy, Bleeding diathesis.
- Ureteroscopy (URS):
- Flexible scope up the ureter. Laser fragmentation.
- Best for: Ureteric stones, Lower pole stones.
- PCNL (Percutaneous Nephrolithotomy):
- Keyhole tract through back into kidney.
- Best for: Large stones (>2cm), Staghorn calculi.
- Sepsis: Urosepsis.
- Renal Failure: Post-renal AKI (bilateral obstruction or solitary kidney).
- Stricture: Ureteric scarring.
- Spontaneous passage likely for stones < 5mm (80%).
- Unlikely for stones > 7mm.
- EAU Guidelines on Urolithiasis.
- BAUS Standards.
What is a kidney stone? It is a hard crystal that forms from chemicals in your urine (usually calcium). It can be as small as a grain of sand or as big as a golf ball.
Why does it hurt so much? When the stone falls out of the kidney into the narrow tube (ureter) draining to the bladder, it gets stuck. The kidney keeps making urine, but it can't get out. The tube stretches and spasms trying to push the stone out, causing excruciating pain.
How do I get it out? Most small stones will pass out on their own if you drink plenty of water and take painkillers. We give you a tablet (Tamsulosin) to relax the tube and help it slide out. If it is too big or stuck, we can blast it with shockwaves from the outside, or use a tiny laser camera to go up and break it into dust.
When is it an emergency? If you have a fever/shivering WITH the pain. This means the blocked urine has become infected and turned into an abscess. We need to drain it immediately to stop blood poisoning.
- Turk C, et al. EAU Guidelines on Urolithiasis. Eur Urol. 2016.
- Pickard R, et al. Medical expulsive therapy in adults with ureteric colic: a multicentre, randomised, placebo-controlled trial (SUSPEND). Lancet. 2015.
- Assimos D, et al. Surgical Management of Stones: AUA/Endourological Society Guideline. J Urol. 2016.