DESCRIPTION

• The term bladder and bowel dysfunction (BBD) generally includes overactive bladder (OAB), dysfunctional voiding, and incomplete defecation.
• OAB is a bladder that manifests reflexive involuntary detrusor contractions at less than expected full capacity beyond the age of toilet training due to lack of CNS inhibition.
• Dysfunctional voiding is defined as obstructed voiding from simultaneous dyssynergic contraction of the pelvic floor with detrusor contraction in the absence of neurologic disease.
• Incomplete defecation manifests as wide stools which clog the toilet, fecal smearing, hard painful stools, and/or infrequent bowel movements (BM) every 3 days or less often.
• Bladder and rectum share embryologic origin from the cloaca as well as synaptic connections in pons and suprapontine brain that modulate mutual function.
• BBD can be transient or long-lasting and is diagnosed by obtaining a detailed history of voiding and bowel elimination habits.

EPIDEMIOLOGY

20% of 6-year-olds have abnormal voiding patterns. Dysfunctional voiding occurs in 5–10% of school-age children.

ETIOLOGY

• OAB results from reflex detrusor contractions, which are not inhibited by higher brain centers.
• Lesions in the CNS can affect bladder and bowel function.

RISK FACTORS

• Delayed maturation of inhibitory CNS control of the bladder is the most common cause of primary OAB in children. Some children have genetic predisposition to OAB, whereas in others, delayed voluntary control of the bladder may be part of generalized developmental delay.
• Incomplete defecation may result from either active stool withholding from passage of hard painful stools, phobia of public bathrooms, restrictions in leaving school classroom, and/or from inadequate pelvic floor relaxation during defecation from inadequate foot support, anxiety, or high pelvic floor tone from previous OAB-induced pelvic withholding maneuvers.

GENERAL PREVENTION

• Children at the toilet-training age should be encouraged to void every 2 to 3 hours when awake.
• Constipation should be prevented and treated with appropriate diet, dietary supplements, and medications.
• Good foot support should be provided at defecation to enable Valsalva maneuver.
• When children express the desire to void or defecate, they should not be asked to hold.

PATHOPHYSIOLOGY

• Physiologically, the bladder stores urine when bladder pressure is lower than the urethral resistance; this occurs due to a relaxed detrusor (bladder muscle) and a closed urethra from a high tone of the pelvic floor (pelvic floor diaphragm and striated urethral sphincter). The bladder empties when bladder pressure rises over the urethral resistance from contraction of the detrusor and reciprocal relaxation of the pelvic floor.
• Reciprocal relationship between detrusor contraction and relaxation of the pelvic floor is mediated by the pontine micturition center (PMC), which acts as the on/off switch for micturition and enables synergic voiding. The lower urinary tract stays in storage mode until activation of the PMC. Infants have reflexive voiding in response to bladder distention mediated by the PMC.
• With CNS maturation, higher brain centers perceive and respond to bladder fullness and can inhibit reflexive voiding, thereby permitting voluntary control of micturition. The latter includes the ability to initiate a void even when the bladder is not full and inhibit voiding despite a full bladder until the time and place is appropriate.
• About 50% of children become dry in the day and night by age 2.5 years and can hold urine comfortably for >2 hours in the day.
• The cardinal manifestation of OAB is urgency of micturition (i.e., the sudden unexpected and compelling desire to pass urine), which is difficult to defer and occurs without prior sensation or warning of bladder fullness.
• Urinary urgency may elicit variable responses in different circumstances, including rushing to the toilet, urge incontinence of full contents of the bladder, or voluntary tightening of the pelvic floor with leakage of just a few drops of urine.
• Volitional pelvic tightening maneuvers include squeezing the thighs together, sucking in the pelvic floor, boys squeezing the penis, and girls sitting and pressing the perineum with their heels.
• Many children find urinary frequency and urgency to be a nuisance and learn to habitually use pelvic tightening maneuvers to postpone voiding and prevent urine leakage rather that rush to the toilet. With OAB, repeated pelvic withholding maneuvers may evolve from a volitional act to prevent urine leakage to a conditioned behavior over time. The children then are unable to relax the pelvic floor even with planned voids and manifest dysfunctional obstructed voiding.
• Incomplete defecation predisposes to the development of OAB and subsequent dysfunctional voiding.
• Giggling may induce a reflex detrusor contraction in those with OAB.

COMMONLY ASSOCIATED CONDITIONS

• Social stress, anxiety, developmental delays, and ADHD during the critical window of toilet training are associated with both delayed maturation of volitional control of bladder and bowel elimination function.
• OAB can result in nocturnal enuresis or nocturia.