Nocturnal enuresis — formative SAQs

SAQ 1 — The school-age child who wets the bed (20 marks, ~15 minutes)

A 7-year-old boy wets the bed on five or six nights a week. He is dry by day, growing normally and otherwise well. 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 would also like the option of quick control for an upcoming school camp. [1]

Questions

1. Define nocturnal enuresis and classify this child's presentation. (5 marks) [1]
2. Outline the focused assessment and the role of investigations, stating what is not routinely needed. (5 marks) [1] [3]
3. Compare the enuresis alarm and desmopressin as first-line therapy, and recommend a plan for this child. (6 marks) [4] [5]
4. State the desmopressin dose and the single most important safety measure. (4 marks) [4] [8]

Model answer (must-hit)

1. Nocturnal enuresis is intermittent involuntary voiding during sleep in a child aged five years or older. This child has monosymptomatic nocturnal enuresis (bedwetting with no daytime symptoms), which is primary (he has never been dry for six months), with nocturnal polyuria on the diary and a strongly positive family history consistent with autosomal dominant inheritance (about a 44 per cent risk with one affected parent). [1]
2. The assessment is a structured voiding and fluid diary, a focused examination of the abdomen, genitalia, spine and lower limbs, and urinalysis. The diary confirms the large overnight urine volume and normal daytime voids. Ultrasound, urodynamics and further imaging are not routine in monosymptomatic enuresis with a normal examination and urinalysis; they are reserved for non-monosymptomatic disease, recurrent infection, abnormal examination or treatment failure. [1] [3]
3. The alarm conditions arousal by pairing the first drops of urine with waking and gives the most durable dryness, with about two-thirds of committed children becoming dry, but it takes weeks and demands a committed family. Desmopressin has a rapid effect, targets nocturnal polyuria directly, and is ideal for short-term control such as a school camp, but relapses on withdrawal. For this motivated family with nocturnal polyuria and an upcoming camp, desmopressin is started for the rapid control, with the alarm offered in parallel or afterwards for durable dryness; the partial responder moves to combination therapy. [4] [5]
4. Desmopressin is given as 200 micrograms orally at bedtime, titrated to 400 micrograms if needed, or 120 to 360 micrograms sublingually. The single most important safety measure is to restrict fluids from one hour before the dose until eight hours after, and to withhold it during vomiting, diarrhoea or systemic illness, to prevent water intoxication and hyponatraemic seizures. [4] [8]

SAQ 2 — New bedwetting with drinking and weight loss, and the child with daytime symptoms (20 marks, ~15 minutes)

An 8-year-old girl who has been dry for two years develops new bedwetting over two weeks. Her mother reports she is thirstier than usual, wakes at night to drink, and has lost 2 kg. Separately, the clinic also sees a 6-year-old boy whose mother reports bedwetting plus daytime urgency, leg-crossing and occasional daytime wetting. [3]

Questions

1. What is the most likely diagnosis in the girl, and what is the urgent next step? (6 marks) [3]
2. Why is the boy's presentation classified differently, and what is the correct first step in his management? (6 marks) [1] [3]
3. Outline the general measures that apply to every child with enuresis before specific therapy. (4 marks) [3]
4. Describe the role and the principal cautions of imipramine in treatment-resistant enuresis. (4 marks) [11]

Model answer (must-hit)

1. The new polyuria, polydipsia, nocturnal drinking and weight loss in a previously dry child is diabetes mellitus until proven otherwise; the bedwetting is secondary to osmotic diuresis. The urgent next step is to check the urine for glucose and ketones and a capillary blood glucose immediately, because hyperglycaemia with ketonuria is diabetic ketoacidosis pending and is managed along the diabetic emergency pathway, not the continence pathway. [3]
2. The boy has daytime urgency, holding postures and daytime wetting alongside the bedwetting, so he has non-monosymptomatic nocturnal enuresis, not monosymptomatic disease. The correct first step is to assess and treat the daytime lower urinary tract symptoms and any constipation, usually with urotherapy and, where appropriate, an anticholinergic, before addressing the night; the daytime bladder dysfunction is the rate-limiting step. [1] [3]
3. The measures that apply to every child are education and reassurance that destigmatise the wetting, a regular fluid intake earlier in the day with a reduction in the evening, regular daytime voiding, treatment of constipation, and treatment of any urinary tract infection, with the explicit message that no child is punished for bedwetting. [3]
4. Imipramine reduces wet nights while the child takes it but relapses on cessation, and it is cardiotoxic in even modest overdose. It is therefore a third-line option reserved for resistant disease under specialist guidance, used in short courses with secure storage, while combination therapy with the alarm plus desmopressin is the evidence-based option for the partial responder before tricyclics are considered. [11]