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Renal stones flashcards

12 high-yield MRCP Part 1 cards from the Intellect Medicos Nephrology course. Try to answer each question before you open it — then study them properly with spaced repetition, which brings each card back just before you would forget it.

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1. What is the first-line imaging for suspected renal colic in a non-pregnant adult, and how quickly?

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   Low-dose non-contrast CT KUB within 24 hours of presentation.

   Why? It detects almost all stones (including uric acid stones), their size and position, and alternative diagnoses.

2. What is the first-line analgesic for renal colic?

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   An NSAID (any route, e.g. IM/PR diclofenac).

   Why? NSAIDs reduce ureteric spasm and renal capsular pressure. Use IV paracetamol if NSAIDs are contraindicated, and opioids only if both are unsuitable.

3. Which drug class is used as medical expulsive therapy for distal ureteric stones under 10 mm?

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   An alpha-blocker (e.g. tamsulosin).

   Why? Relaxing ureteric smooth muscle helps the stone pass. NICE says 'consider' (off-label), after evidence reviewed since the SUSPEND trial.

4. For a ureteric stone of 10–20 mm the preferred treatment is ______; for a renal stone over 20 mm or a staghorn calculus it is percutaneous nephrolithotomy (PCNL).

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   ureteroscopy

   Why? Shockwave lithotripsy (SWL) suits smaller stones (<10 mm, and renal stones up to 20 mm). Asymptomatic renal stones <5 mm can be watched.

5. For a ureteric stone of 10–20 mm the preferred treatment is ureteroscopy; for a renal stone over 20 mm or a staghorn calculus it is ______.

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   percutaneous nephrolithotomy (PCNL)

   Why? Shockwave lithotripsy (SWL) suits smaller stones (<10 mm, and renal stones up to 20 mm). Asymptomatic renal stones <5 mm can be watched.

6. Which patient group has an absolute contraindication to shockwave lithotripsy, and so has ureteroscopy instead?

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   Pregnant women.

   Why? In pregnancy, ureteroscopy is the definitive treatment, with a ureteric stent or nephrostomy for temporary drainage.

7. A patient with a ureteric stone has fever, rigors and hydronephrosis. What is the immediate management after antibiotics?

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   Urgent decompression of the kidney — percutaneous nephrostomy or retrograde ureteric (JJ) stent.

   Why? An infected obstructed kidney can cause rapid sepsis and loss of the kidney. Definitive stone treatment is delayed until the infection settles.

8. Which renal stones are radiolucent on plain X-ray?

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   Uric acid (urate) stones (and rare xanthine stones).

   Why? Calcium oxalate (the commonest stone), calcium phosphate and struvite are radio-opaque; cystine is semi-opaque. Uric acid stones form in acidic urine.

9. Which organism classically causes struvite (staghorn) calculi, and how?

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   Proteus mirabilis — urease splits urea into ammonia, making the urine alkaline.

   Why? Struvite (magnesium ammonium phosphate) precipitates in alkaline urine and has 'coffin-lid' crystals.

10. Which diuretic class is used to prevent recurrent calcium stones in hypercalciuria?

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    Thiazide diuretics.

    Why? Thiazides increase distal tubular calcium reabsorption, lowering urinary calcium. NICE suggests them for recurrent mainly calcium oxalate stones with hypercalciuria, after sodium intake is cut to 6 g/day or less. Loop diuretics do the opposite.

11. What drug treatments prevent recurrent uric acid stones?

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    Urinary alkalinisation (potassium citrate or sodium bicarbonate) and allopurinol.

    Why? Uric acid is much more soluble in alkaline urine; allopurinol lowers uric acid production.

12. Name two drugs that increase the risk of calcium stones.

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    Any two of: loop diuretics, acetazolamide, corticosteroids, theophylline.

    Why? These increase urinary calcium or (acetazolamide) produce alkaline urine with low citrate.