Causes of Nocturnal Enuresis
Nocturnal enuresis is primarily a biological disorder with strong genetic underpinnings, not a psychological problem, involving three core pathophysiological mechanisms: nocturnal polyuria, detrusor overactivity, and increased arousal threshold. 1
Genetic and Hereditary Factors
The genetic component is the strongest predictor of nocturnal enuresis. Children face a 44% risk when one parent had enuresis and a staggering 77% risk when both parents were affected, compared to only 15% in children from non-enuretic families. 2, 1 Specific chromosomal loci have been identified that link directly to enuresis, confirming this hereditary basis. 2, 1
Primary Pathophysiological Mechanisms
The three major mechanisms that cause the mismatch between bladder capacity and nighttime urine production are:
Nocturnal polyuria: Excessive urine production at night due to abnormal secretion of antidiuretic hormone, resulting in nocturnal urine production exceeding 130% of expected bladder capacity for age. 1, 3, 4
Detrusor overactivity/reduced bladder capacity: Uninhibited bladder contractions and decreased functional bladder capacity (maximum voided volume <70% of expected capacity for age), often with occult bladder dysfunction. 1, 3, 4
Dysfunctional arousal system: Inability to awaken from sleep in response to bladder distention, occurring randomly across all sleep stages. 2, 5
Sleep-Related Causes
Obstructive sleep apnea from upper airway obstruction (enlarged adenoids or tonsils) is a specific and treatable cause of enuresis. 2 Surgical correction of upper airway obstruction can lead to improvement or cure of enuresis. 2, 1 Screen for habitual snoring, witnessed apneas or gasping during sleep, restless sleep or unusual sleeping positions, and daytime sleepiness or behavioral problems. 1
Developmental and Neurological Factors
Developmental immaturity, including delayed motor and language milestones, contributes to enuresis etiology in some children, though the exact mechanism remains unknown. 2 Neurologic dysfunction and spinal cord anomalies should be excluded during physical examination. 2
Gastrointestinal Causes
Constipation and fecal impaction cause mechanical pressure on the bladder, frequently leading to enuresis. 2 Disimpaction and establishing a healthy bowel regimen often eliminates the enuresis. 2
Urological and Medical Conditions
Several medical conditions are associated with enuresis and require specific evaluation:
- Urinary tract infections and genitourinary abnormalities 2, 5
- Diabetes mellitus and diabetes insipidus 5, 6
- Chronic kidney disease 5
- Recurrent urinary tract infections or urinary tract malformations 5
Psychological Factors (Minority of Cases)
Identifiable psychological factors are contributory in only a minority of children with enuresis, contrary to common misconceptions. 2, 7 These are most frequently seen in secondary enuretics who experienced specific stressors such as parental divorce, school trauma, sexual abuse, or hospitalization—the enuresis represents a regressive symptom in response to stress or trauma. 2
Psychological factors may also be central in rare instances of family disorganization or neglect where toilet training was never reasonably attempted, though other signs of neglect are usually evident. 2
Critical Distinction: Primary vs. Secondary Enuresis
Secondary enuresis (resumption of wetting after ≥6 months of dryness) warrants prompt evaluation as it may indicate underlying medical conditions, psychological stressors, or life events requiring separate treatment. 7, 6 Primary enuresis (never been consistently dry) is more likely to have biological underpinnings with the genetic and pathophysiological mechanisms described above. 2
Common Pitfall to Avoid
Do not assume psychological causation in most cases of enuresis. The disorder has biological underpinnings in the vast majority of children, and psychological factors are contributory in only a minority. 7, 6, 8 Bedwetting is not primarily caused by an underlying psychological disorder, though psychological problems and life events can exacerbate or precipitate bedwetting in susceptible children who have a genetic basis for their condition. 6