NephrologyTier 2Disease (DEADMAN)

Nephrolithiasis

Description

Kidney stone disease - crystal aggregates form in the urinary tract, most commonly calcium oxalate (~80%), then calcium phosphate, uric acid, struvite (infection stones), and cystine (rare, genetic)
Presents with renal colic - severe, colicky flank pain radiating to the groin; classically the patient is unable to lie still (distinguishing it from peritonitic pain)

Lifetime risk ~10-15% in developed countries; M>F (~2-3:1); peak age 30-50 years; recurrence in ~50% within 5-10 years without prevention

Supersaturation of urine with stone-forming solutes -> crystal nucleation and aggregation
Risk factors: low fluid intake, high dietary sodium/animal protein/oxalate, obesity, hypercalciuria, hyperuricosuria, hypocitraturia, anatomical abnormalities (horseshoe kidney, medullary sponge kidney), recurrent UTI (struvite), inflammatory bowel disease (enteric hyperoxaluria)
Struvite stones form only with urease-producing organisms (Proteus, Klebsiella) - alkaline urine, can form large "staghorn" calculi

Non-contrast CT KUB - gold standard, detects >99% of stones regardless of composition
Renal tract ultrasound - first-line in pregnancy/children (avoids radiation), less sensitive for small/ureteric stones
Urinalysis (haematuria in ~85%, though its absence does not exclude a stone); stone analysis if passed/retrieved; metabolic workup (serum calcium, urate, 24-hour urine) after a first stone in a high-risk patient or recurrent stones

Analgesia - NSAIDs first-line (also reduce ureteric spasm/oedema), opioids if needed
<=5-6mm - high likelihood of spontaneous passage; medical expulsive therapy (tamsulosin) may help for distal ureteric stones, though evidence has weakened in recent trials
>=7mm or failed conservative management - ureteroscopy with laser lithotripsy, extracorporeal shock wave lithotripsy (ESWL), or percutaneous nephrolithotomy (PCNL) for large/staghorn calculi, chosen by stone size/location
Infected obstructed system (pyonephrosis) - urological emergency - urgent decompression (stent or nephrostomy) + antibiotics, stone treatment deferred until infection is controlled

Hyperparathyroidism (hypercalciuria), gout (uric acid stones), inflammatory bowel disease, recurrent UTI, obesity/metabolic syndrome

Prevention (fluid intake >=2.5L/day, dietary sodium/oxalate/animal protein moderation, thiazides for hypercalciuria, citrate supplementation) reduces recurrence substantially
Untreated obstruction risks AKI (if bilateral or single functioning kidney) and infection - the two indications that escalate management from conservative to urgent intervention

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