Nocturnal enuresis — structured clinical encounter

Station brief (candidate)

You are the paediatric registrar in a general clinic. A 7-year-old boy is referred because he wets the bed on five or six nights a week. He is dry by day, growing normally and otherwise well, and his father wet the bed until age 11. A voiding diary shows a large overnight urine volume with normal daytime voids, and urinalysis is normal. The family is motivated and able to wake with the child, but they would also like the option of quick control for an upcoming school camp. The team asks you to establish the definition and classification, outline the assessment and investigations, choose and justify the first-line therapy, and counsel on the desmopressin safety measures. You have 12 minutes with the team and 5 minutes for examiner discussion. [1]

Information available on request

• 7-year-old boy; bedwetting on five or six nights a week; dry by day; growing normally; otherwise well. [1]
• Father wet the bed until age 11; mother was never enuretic. [3]
• Voiding and fluid diary (on request): large overnight urine volume, dilute, well above the expected bladder capacity for age; normal daytime voids. [4]
• Urinalysis (on request): specific gravity low on the morning sample, glucose negative, protein negative, leucocytes and nitrites negative. [3]
• Examination (on request): abdomen soft, no distended bladder or faecal loading; genitalia normal; spine and lower-limb neurological examination normal; blood pressure normal. [3]

Tasks

1. Define nocturnal enuresis and classify this child's presentation. [1]
2. Outline the assessment and investigations, stating what is not routinely needed and why. [1] [3]
3. Compare the enuresis alarm and desmopressin and recommend a first-line plan for this child. [4] [5]
4. State the desmopressin dose and the single most important safety measure you would teach the family. [4] [8]
5. Describe the next step if the child only partially responds to a single agent. [11]

Marking anchors

Must-hit

• Defines nocturnal enuresis as involuntary voiding during sleep in a child aged five or older and classifies this child as monosymptomatic primary enuresis with nocturnal polyuria and a positive family history (about a 44 per cent risk with one affected parent, autosomal dominant). [1]
• States that the assessment is a voiding and fluid diary and urinalysis with a focused examination, and that ultrasound and urodynamics are not routine in monosymptomatic disease with a normal examination and urinalysis. [1] [3]
• Recommends desmopressin for this child given the nocturnal polyuria and the need for rapid short-term control, at 200 micrograms orally titrated to 400 micrograms or 120 to 360 micrograms sublingually at bedtime, with the alarm offered alongside or afterwards for durable dryness; and teaches the fluid-restriction rule of restricting fluids from one hour before the dose until eight hours after and withholding the drug during illness. [4] [8]

Merit

• Identifies that the partial responder moves to combination therapy with the alarm plus desmopressin, ranked among the most effective options, with a structured taper or alarm overlap to reduce the relapse rate on withdrawal; and reserves imipramine as a third-line option because of cardiotoxicity in overdose and relapse on cessation. [11]

Fail

• Reassures the family that the bedwetting is purely behavioural and prescribes no assessment or treatment despite the distress and the upcoming camp. [1]
• Prescribes desmopressin without teaching evening fluid restriction, or recommends the intranasal spray for a faster effect. [4]