Symptomatic 10–20 mm renal calculus unsuitable for shockwave lithotripsy — MSRA MCQ

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ModerateNephrolithiasisSymptomatic 10–20 mm renal calculus unsuitable for shockwave lithotripsyMSRA

A 45-year-old woman is reviewed in a stone clinic after three episodes of left-sided renal colic over 6 months. Low-dose non-contrast CT shows a 16 mm left renal pelvic calculus. Renal function is normal, urine culture is negative and there is no hydronephrosis. The stone is not targetable with shockwave lithotripsy because of unfavourable anatomy confirmed by the lithotripsy service. She wishes definitive treatment. What is the most appropriate management plan?

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Correct answer: B — Proceed with ureteroscopy and laser lithotripsy

Explanation lettering: B = shown as A · D = shown as B · A = shown as C · E = shown as D · C = shown as E

This is a symptomatic 16 mm renal stone, so watchful waiting is inappropriate given recurrent colic and the patient's preference for definitive treatment. For adult renal stones measuring 10–20 mm, NICE recommends considering either ureteroscopy (URS) or shockwave lithotripsy (SWL). Here, SWL is not technically feasible because the stone is not targetable; therefore URS with laser lithotripsy is the appropriate definitive option. A is initially attractive because SWL is a guideline-supported option for renal stones of this size, but it is unsuitable when targeting is not possible. B is more invasive than necessary: percutaneous nephrolithotomy is considered for 10–20 mm renal stones after URS or SWL has failed, rather than as first-line treatment in this situation. C would be reasonable only for an asymptomatic renal stone after informed discussion; this patient has recurrent renal colic. E does not overcome the inability to target the stone with SWL, and NICE advises against routine pre-treatment stenting before SWL in adults.

Reference: Renal and ureteric stones: assessment and management (NG118) — Recommendations (2019) — https://www.nice.org.uk/guidance/ng118/chapter/Recommendations Renal and ureteric stones: assessment and management (NG118) — Stenting before shockwave lithotripsy (2019) — https://www.nice.org.uk/guidance/ng118/chapter/Recommendations Renal and ureteric stones: assessment and management (NG118) — Watchful waiting for asymptomatic renal stones (2019) — https://www.nice.org.uk/guidance/ng118/chapter/Recommendations