What are the causes of enuresis?

Causes of Enuresis

The primary causes of enuresis include genetic factors, developmental delay, sleep arousal disorders, reduced functional bladder capacity, and psychological factors, with genetic predisposition being the strongest contributor in most cases. 1

Genetic Factors

• Strong familial pattern with 44% of children developing enuresis when one parent was enuretic and 77% when both parents were enuretic, compared to only 15% in children from non-enuretic families 1
• Specific genetic loci have been identified on chromosomes 13 (ENUR 1) and 12 (ENUR 2), confirming the genetic basis of the condition 1
• Approximately one-third of fathers and one-fifth of mothers of enuretic children were themselves enuretic as children 1

Sleep Pattern Abnormalities

• Dysfunctional arousal system during sleep is a key etiologic factor for a subgroup of children with enuresis 1
• Three distinct patterns of sleep-related enuresis have been identified through EEG and cystometry studies 1:
  • Type I: Detectable EEG response to bladder distention without awakening
  • Type IIa: No EEG response to bladder distention and no bladder contractions (similar to infant pattern)
  • Type IIb: No arousal on EEG but unstable bladder contractions leading to enuresis 1
• Sleep disorders such as sleep apnea and narcolepsy are associated with enuresis 1
• Children with enuresis typically require louder stimuli to awaken compared to non-enuretic children 1

Developmental Delay

• Developmental immaturity in attaining central control of bladder function is considered a primary etiology by many pediatricians 1
• Reduced functional bladder capacity is common in children with enuresis 1
• Uninhibited bladder contractions (similar to infantile pattern) are more common in urodynamic studies of enuretic children 1
• Higher incidence of enuresis in children with delayed motor and language milestones 1
• Physical characteristics suggesting developmental immaturity include lower average height and bone age in enuretic children 1

Bladder Function Abnormalities

• Reduced functional bladder capacity compared to non-enuretic children 1
• Normal functional bladder capacity can be estimated using the formula: "age in years + 2 = functional bladder capacity in ounces" 1
• Uninhibited bladder contractions similar to infantile voiding patterns are more common in enuretic children 1

Psychological Factors

• Psychological factors are clearly contributory in a minority of children with enuresis, particularly in secondary enuresis 1
• Stressful life events such as parental divorce, school trauma, sexual abuse, or hospitalization can trigger secondary enuresis 1
• Family disorganization or neglect resulting in inadequate toilet training can contribute to enuresis 1
• Medications such as lithium, valproic acid, clozapine, and theophylline can cause secondary enuresis as a side effect 1

Medical Conditions

• Constipation and fecal impaction can cause mechanical pressure on the bladder leading to enuresis 1
• Upper airway obstruction and sleep apnea are associated with enuresis, with surgical correction often resolving the condition 1
• Other medical conditions associated with enuresis include diabetes mellitus, diabetes insipidus, chronic kidney disease, and urinary tract infections 2

Clinical Subtypes

• Primary enuresis: Children who have never been consistently dry through the night 1
• Secondary enuresis: Resumption of wetting after at least 6 months of dryness 1
• Nocturnal enuresis: Voiding during sleep 1
• Diurnal enuresis: Wetting while awake 1
• Monosymptomatic: Nocturnal bed-wetting is the only symptom 3
• Non-monosymptomatic: Both daytime and nighttime symptoms are present 3

Pathophysiological Mechanisms

• Three key factors contribute to nocturnal enuresis 4:
  1. Excessive nocturnal urine production
  2. Nocturnal bladder dysfunction
  3. Impaired sleep arousal mechanisms
• Two main pathophysiological types 4:
  • Diuresis-dependent enuresis: Excessive nocturnal urine production with impaired arousal
  • Detrusor-dependent enuresis: Nocturnal detrusor hyperactivity with impaired arousal

Understanding these various causes is essential for appropriate assessment and targeted treatment of enuresis, as the underlying etiology will guide the most effective therapeutic approach 1.