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Q1: The classic presentation (2 min)
"A patient has sudden flank pain radiating to the groin. What is the diagnosis, the bedside discriminator, and the gold-standard imaging?"
- Renal/ureteric colic from a stone — loin-to-groin, fluctuating colicky pain, nausea, haematuria.
- The patient WRITHES and cannot settle (visceral pain) vs the STILL peritoneal patient — the classic discriminator.
- Gold standard: NON-CONTRAST CT KUB (95-98% sensitive); ultrasound first-line in pregnancy and children.
Q2: Stone types (3 min)
"Name the four classical stone types and one key feature of each."
- Calcium oxalate — commonest (~75%); radio-opaque, spiky envelope crystals; hypercalciuria, hyperparathyroidism, IBD.
- Uric acid — radio-LUcent; acidic urine (pH under 5.5), gout; DISSOLVES with alkalinisation.
- Struvite — magnesium ammonium phosphate; urease-producing Proteus; alkaline urine (pH >7.2); staghorn.
- Cystine — autosomal-recessive cystinuria (SLC3A1/SLC7A9); hexagonal crystals; cyanide-nitroprusside.
- Trap: E. coli does NOT produce urease.
Q3: Management by size (3 min)
"How would you manage a 4 mm, 8 mm, and 25 mm renal stone?"
- 4 mm: conservative — ~80% pass; analgesia (NSAIDs), hydration; tamsulosin not routine at under 5 mm.
- 8 mm distal ureter: MET trial (tamsulosin 0.4 mg nocte, ~50% pass); if failed — ureteroscopy + Holmium laser (>90% stone-free).
- 25 mm kidney / staghorn: PCNL is the gold standard for stones >20 mm and staghorn.
- Kidney under 20 mm: ESWL or retrograde intrarenal surgery; proximal ureter under 20 mm: ESWL or URS.
Q4: The emergency (2 min)
"A patient with a ureteric stone has fever 39C, rigors and a rising creatinine. What do you do?"
- This is an OBSTRUCTED INFECTED SYSTEM with AKI = urological emergency (pyonephrosis / urosepsis).
- Cultures + IV broad-spectrum antibiotics + resuscitation.
- Urgent decompression: JJ stent (retrograde) or percutaneous nephrostomy — BEFORE definitive stone treatment.
- Do NOT ESWL or ureteroscope in untreated infection (risk of sepsis). Definitive stone removal once afebrile and culture-clear.
Q5: Prevention (3 min)
"A 50-year-old man has had three calcium stones in five years. What is your preventive strategy?"
- Work-up: two 24-hour urines (volume, calcium, oxalate, citrate, urate, sodium, phosphate, cystine screen); serum calcium and PTH, urate.
- General measures: fluids over 2.5-3 L/day (urine output over 2 L), low sodium (under 100 mmol/day), moderate animal protein, NORMAL dietary calcium (not low — low calcium increases oxalate absorption), restrict oxalate.
- Targeted: hypercalciuria → thiazide (+ potassium citrate to prevent hypocitraturia); hypocitraturia → potassium citrate.
- If hypercalcaemic → measure PTH; primary hyperparathyroidism → parathyroidectomy (curative).
- Halves recurrence (15%/yr → ~7%/yr).
Q6: Special situations (2 min)
"How does management change in pregnancy, and in a patient with a solitary kidney?"
- Pregnancy: ultrasound first-line (avoid CT); paracetamol, avoid NSAIDs after 32 weeks (ductus arteriosus, oligohydramnios); ESWL contraindicated; an obstructed/infected system is decompressed with a temporary JJ stent or nephrostomy, definitive therapy deferred postpartum.
- Solitary kidney: ANY obstruction is an emergency — urgent decompression to preserve the only renal unit; monitor renal function closely.