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Benign prostatic enlargement with nocturnal polyuria — MSRA MCQ

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HardBPHBenign prostatic enlargement with nocturnal polyuriaMSRA

A 64-year-old man with benign prostatic enlargement takes tamsulosin MR 400 micrograms daily and finasteride 5 mg daily. His previous hesitancy, weak stream and incomplete emptying have improved substantially. He now reports persistent nocturia four times nightly, causing marked sleep disruption. He has no urgency, urge incontinence, dysuria, haematuria or recurrent urinary tract infection. A 3-day frequency-volume chart shows total urine output of 1.8 L per 24 hours, of which 780 mL is passed overnight. Maximum voided volume is 410 mL. Urine dipstick is negative. eGFR is 78 mL/min/1.73 m², serum sodium is 140 mmol/L, HbA1c and adjusted calcium are normal, and there is no heart failure, peripheral oedema, obstructive sleep apnoea, liver disease or diuretic, calcium-channel blocker or SSRI use. Fluid timing, caffeine reduction and a trial of a late-afternoon loop diuretic have not improved symptoms. What is the most appropriate next management step?

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

Reveal the answer and explanation

Correct answer: E — Start desmopressin 50 micrograms sublingually one hour before bed, with overnight fluid restriction and serum sodium measurement after 3 days

Explanation lettering: B = shown as A · A = shown as B

The frequency-volume chart demonstrates nocturnal polyuria: a disproportionately large proportion of his 24-hour urine output is produced overnight, despite a normal total daily volume and preserved functional bladder capacity. His voiding symptoms have responded to treatment for benign prostatic enlargement, and he has neither urgency nor urge incontinence to suggest persisting overactive bladder. Escalating outlet-directed treatment is therefore unlikely to address the dominant mechanism. NICE advises considering oral desmopressin for nocturnal polyuria after relevant medical causes have been excluded and other treatments have failed, with serum sodium checked 3 days after starting. This patient has normal renal function and sodium, and the key alternative systemic and medication-related causes have been excluded. He should also receive clear advice to restrict fluid intake from 1 hour before until 8 hours after dosing. A is inappropriate because tamsulosin is already at the usual MR dose and obstruction is not the current problem. B would be reasonable for persistent storage symptoms, particularly urgency or urge incontinence, but these are absent. C may reduce progression risk in an enlarged prostate but will not selectively treat nocturnal polyuria. D is not indicated in a man without red flags, recurrent infection, retention, haematuria, pain or treatment-refractory voiding symptoms.

Reference: NICE CG97: Lower urinary tract symptoms in men: management, recommendations (2015) — https://www.nice.org.uk/guidance/cg97/chapter/recommendations NICE CG97: Lower urinary tract symptoms in men: management, recommendations (2015) — https://www.nice.org.uk/guidance/cg97/chapter/recommendations Noqdirna 25 microgram oral lyophilisate Summary of Product Characteristics (Updated 15 June 2026) — https://www.medicines.org.uk/emc/product/4368/smpc