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Kidney stones and renal colic
Renal colic is treated first with NSAIDs and diagnosed with low-dose non-contrast CT (ultrasound in pregnancy), and an obstructing ureteric stone with infection is an emergency needing urgent drainage; to prevent recurrence, drink plenty and do not restrict dietary calcium.
Why it matters in the exam
The question presents sharp, wave-like flank pain radiating to the groin, with nausea and blood in the urine. The preferred test is low-dose non-contrast CT; in pregnancy and young people ultrasound comes first. NSAIDs (for example diclofenac) are preferred over opioids as first treatment. A stone smaller than 5 mm usually passes on its own; for a distal ureteric stone of 5–10 mm, tamsulosin increases the chance of passage; a stone larger than 10 mm usually needs intervention (ureteroscopy or lithotripsy). The important exception: fever with an obstructing stone — urgent drainage (stent or nephrostomy) and antibiotics, not lithotripsy.
Another part is stone type and prevention. Calcium oxalate stones are the commonest; uric acid stones are invisible on plain X-ray but visible on CT, form in acid urine and are treated with alkalinisation (potassium citrate); struvite ("staghorn") stones are linked to infection with urea-splitting bacteria (Proteus); cystine stones are hexagonal and inherited. Prevention: drink enough for a urine output above 2.5 litres a day, normal dietary calcium (restricting calcium actually increases stones), less salt and animal protein; a thiazide for hypercalciuria, potassium citrate for hypocitraturia, and a metabolic work-up with 24-hour urine in recurrent stone formers.
Key points
- Low-dose non-contrast CT; ultrasound in pregnancy.
- NSAIDs for pain; tamsulosin for a distal stone of 5–10 mm.
- Above 10 mm — intervention; below 5 mm — usually passes.
- Fever with an obstructing stone — urgent drainage and antibiotics.
- Prevention: urine above 2.5 litres, normal calcium, less salt; thiazide for hypercalciuria.
Summary table
| Topic | Finding | Action | Exam note |
|---|---|---|---|
| Diagnosis | Flank-to-groin pain, haematuria | Low-dose non-contrast CT; ultrasound in pregnancy | Check temperature and creatinine |
| Pain | Colic | NSAIDs first | Preferred over opioids |
| Small stone | Below 5 mm | Wait and drink | Usually passes on its own |
| Distal stone 5–10 mm | In the ureter | Tamsulosin | Expulsive therapy |
| Stone above 10 mm or failure | — | Ureteroscopy or lithotripsy | Large renal stone: PCNL |
| Obstruction with infection | Fever + obstructing stone | Urgent drainage (stent or nephrostomy) + antibiotics | No lithotripsy with active infection |
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Sources
- EAU Guidelines on Urolithiasis, 2024 — Diagnostic imaging, analgesia, medical expulsive therapy and intervention
- AUA Guideline: Medical Management of Kidney Stones, 2019 — Metabolic evaluation and prevention
- Harrison's Principles of Internal Medicine, 21st edition (2022) — Nephrolithiasis
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.