Urinary incontinence is a normal developmental stage. When present beyond a certain age defined by parental and societal expectations, it can cause concern and anxiety in the patient and family. Urinary incontinence can also be a symptom of significant pathologic processes. The challenge to the clinician is identifying the child with an organic disorder among the many who are proceeding along a normal developmental track.
Voiding Physiology
(See Nelson Textbook of Pediatrics, p. 2584.)
Urinary continence is dependent on normal bladder function and normal urine production. Normal development of bladder function results in the storage and release of urine in a socially and physically acceptable way. During storage, the detrusor muscle is relaxed, and the capacity of the bladder allows urine to be held for several hours. Micturition is then voluntary, with coordinated detrusor contraction and sphincter relaxation, resulting in complete bladder emptying. The bladder capacity in children learning to be toilet trained is variable, being dependent on their own sensation of bladder fullness. The maximum functional bladder capacity may differ greatly among children when measured by home diaries. Cystometry, a method of measuring bladder volume, can be estimated by the following 2 formulas:
In children <2 years of age:
Cystometric bladder capacity ( ounces ) = ( 2 × age [ years ] ) + 2
In children ≥2 years of age:
Cystometric bladder capacity ( ounces ) = age ( years ) 2 + 6
Although the innervation of the bladder is predominantly autonomic, bladder function is under control of cortical function. Thus, a complex integration of visceral and somatic innervation is necessary for normal voiding, which perhaps explains the wide spectrum in the ages for urinary continence. Parasympathetic neural activity provides the primary input during micturition, leading to relaxation of the urethral smooth muscle and initiating detrusor contractions. Pelvic nerves conducting parasympathetic activity form a reflex arc with the centrally located pontine micturition center. The thoracolumbar sympathetic branch, via hypogastric and pelvic sympathetic nerves, innervates the detrusor to relax and the urinary sphincter to contract during urine storage.
Urinary continence thus relies on the abilities to (1) store urine without leakage, (2) release urine voluntarily and completely, and (3) interrupt micturition voluntarily. The third ability is indicative of fully coordinated cortical-autonomic function.
Toilet Training
(See Nelson Textbook of Pediatrics, p. 2581.)
The age at which toilet training is achieved is influenced by cultural factors as well as the individual temperament of the child. The achievement of daytime urinary continence follows the attainment of bowel control. There is evidence that the age of daytime and nighttime continence has increased worldwide in the past century. Data suggest a change in parental attitudes toward the toilet training process and their expectations. Temperament of the child and cognitive ability may play a less significant role. Among social factors, children of single parents are successfully toilet trained at an earlier age, whereas enrollment in daycare does not have a significant influence. Consistent findings are the predictive factors of gender and race: Girls are toilet trained earlier than boys, and African-American children are trained earlier than white children. Techniques for toilet training are varied and range from the child-oriented approach to single-day training intensive methods to the use of daytime wet alarms.
Urine Volume and Solute Diuresis
Polyuria is the overproduction of urine. Polyuria is a symptom that is fixed and therefore occurs during both the daytime and the nighttime. “Nocturnal polyuria,” a symptom proposed in a subset of patients with primary nocturnal enuresis, is discussed separately. Overproduction of urine indicates a defect in 1 of several mechanisms regulating water and solute homeostasis. Identification of children with incontinence caused by polyuria is essential for diagnosing a variety of disorders ( Table 45.1 ).
| With Polyuria |
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| Without Polyuria |
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