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Nocturnal polyuria secondary to suspected obstructive sleep apnoea — MSRA MCQ

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HardLUTSNocturnal polyuria secondary to suspected obstructive sleep apnoeaMSRA

A 64-year-old man reports waking three times nightly to pass urine for 9 months. He has no urgency, urge incontinence, hesitancy, weak stream, intermittency or sensation of incomplete emptying. His IPSS is 7. Urine dipstick is negative for blood, leucocytes, nitrites and glucose. DRE shows a smooth prostate estimated at 35 g; following discussion, PSA is 1.8 micrograms/L. A 3-day frequency-volume chart shows a mean 24-hour urine output of 2.2 L, of which 1.1 L is passed overnight. Each nocturnal void is large volume. He has no ankle oedema, heart failure symptoms, renal impairment, hypercalcaemia, diabetes or diuretic use. He has reduced evening fluid and caffeine intake without benefit. His partner reports loud habitual snoring, witnessed pauses in breathing and unrefreshing sleep. He has troublesome daytime sleepiness. What is the most appropriate next management step for his nocturia?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: A — Arrange sleep-clinic assessment for suspected obstructive sleep apnoea before nocturia-specific drug treatment

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

The frequency-volume chart demonstrates nocturnal polyuria: half of his 24-hour urine output is produced overnight, with large nocturnal voids. This is not a storage-symptom pattern, because there is no urgency or small-volume frequency, and it is not primarily bladder outlet obstruction, because he has no voiding symptoms and only mild overall LUTS. His loud snoring, witnessed apnoeas, non-restorative sleep and daytime somnolence make obstructive sleep apnoea a likely reversible contributor. NICE specifically lists obstructive apnoea among medical causes of nocturnal polyuria. Therefore, this should be assessed before prescribing nocturia-directed medication. NHS guidance supports referral to a sleep clinic when a GP suspects sleep apnoea. Alpha-blocker therapy (A) would be appropriate for bothersome moderate-to-severe voiding LUTS, which he does not have. Desmopressin (C) can be considered for nocturnal polyuria only after other medical causes have been excluded and other measures have failed. A late-afternoon loop diuretic (D) is a possible option for nocturnal polyuria, particularly where fluid redistribution contributes, but does not address the strong suspicion of sleep apnoea in this case. Anticholinergic therapy (E) treats overactive bladder symptoms, which are absent.

Reference: NICE CG97: Lower urinary tract symptoms in men: management — Recommendations (Published 2010; last updated 3 June 2015; last reviewed 19 December 2024) — https://www.nice.org.uk/guidance/cg97/chapter/recommendations NICE CG97: Lower urinary tract symptoms in men: management — Drug treatment (Published 2010; last updated 3 June 2015; last reviewed 19 December 2024) — https://www.nice.org.uk/guidance/cg97/chapter/recommendations NHS: Sleep apnoea (2026) — https://www.nhs.uk/conditions/sleep-apnoea/