An Underreported Symptom of AN: Bedwetting

Most teens and adults do not
reveal their symptoms.

Reprinted from Eating Disorders Review
May/June 2011 Volume 22, Number 3
©2011 Gürze Books

Some time ago, clinicians with the Eating Disorders Program at the Hospital for Sick Children in Toronto, Canada, began noticing that a number of children and teens with anorexia nervosa (AN) had secondary nocturnal enuresis (bedwetting). When Nuray Kanbur, MD and colleagues administered a self-report urinary incontinence survey (Incontinence Symptom Index-Pediatric, or ISI-P) to patients whose enuresis had appeared at about the time AN developed, they found the prevalence of nocturnal enuresis (NE) was 17% (10 of 59 patients). They also learned that there was little information about NE in patients with AN (Int J Eat Disord 2011; 44:349). This is the first study to investigate bladder dysfunction in teens with AN.

Dr. Kanbur and colleagues found that the overall frequency of daytime and nighttime urinary incontinence symptoms was 62.7%. Stress incontinence affected 32.2% of all participants and 60% (6 of 10) participants with NE, which suggested the possibility of an underlying bladder dysfunction caused by detrusor instability (uncontrolled contractions of the bladder wall). All cases of secondary enuresis resolved after weight was restored.

Several mechanisms are involved

NE is a heterogeneous disorder with various underlying mechanisms that result in two main types of enuresis, nocturnal polyuresis (diuresis-dependent enuresis) and reduced functional bladder capacity, or detrusor instability (involuntary contractions of the bladder wall). It’s still unclear why adolescents with AN develop secondary NE. AN has been associated with abnormal osmoregulation and impaired urinary concentrating capacity, and some reports suggest it may be related to hypothalamic dysfunction or a primary renal problem. One study of patients with AN who were taking antidepressants found the patients had a blunted ability to concentrate urine in comparison with healthy controls (Nephrol Dial Transplant 2004; 19:3034).

The authors discovered that two patients had altered bladder dynamics and supranormal curves on uroflow measures, which pointed to voiding dysfunction. One had a low body mass index  and the other had functional constipation with episodes of encopresis while she had NE.

One interesting sidelight was that none of the teens with AN in the study population reported symptoms of NE until specifically asked about it on the questionnaire. Concealment of this problem warrants further investigation; for example, the authors note that in a study of adults with NE, half of men and 35% of women had never consulted a clinician about their symptoms and only 30% believed that bedwetting was treatable (Scand J Urol Nephrol 1997; 31:533).

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