Uninhibited detrusor contractions

By the age of 4-5 years many children have been toilet-trained successfully and have adopted an adult pattern of urinary control. This is also characterized by the absence of involuntary or uninhibited detrusor contractions during bladder fiUing. Even if the bladder is full and there is a strong desire to void, no bladder contractions will occur. With micturition, coordinated relaxation of the external urethral sphincter takes place. Therefore, bladder emptying is under low intravesical pressure in children and adults. 

The clinical symptoms of unstable bladder (over-active bladder) are frequency, urge and urge incontinence. Uninhibited detrusor contractions leading to symptoms such as urgency, frequency and urge incontinence can be called overactive bladder syndrome (Staskin and Dmochowski 2002). 

Fig. 14.2a-c. Male, 2 months old moderate bilateral fetal hydronephrosis, VCU. Reduced bladder filling volume (20 ml) residual urine early uninhibited detrusor contractions transformed into premature micturition, a Minor bladder trabecu-lation, short phase of normal micturition. b,c Dyscoordinated voiding, contraction of external urethral sphincter dilated posterior urethra, male spinning top urethra... 

The combination of a transient opening of the bladder neck with a flow of contrast material into the posterior urethra up to the voluntarily contracted striated urethral sphincter (Potter et al. 1986 Passerini-Glazel et al. 1992) together with cessation and/or back-up of contrast material drip flow suggests the presence of an uninhibited detrusor contraction (Fig. 14.3). These findings are valid they can stand alone without urodynamic results. Modified VCU allows detection of the majority of these dysfunctions in neonates, infants and small children with the same reliability and in the same way as in older age groups. 

Second, the so-called wide bladder neck anomaly (WBNA) (Saxton et al. 1988 Hoebecke et al. 1999) is a permanent passive bladder-neck opening in the filling phase of the VCU independent of uninhibited detrusor contractions (Fig. 14.5). Wide bladder neck anomaly might be an acquired phenomenon and unstable bladder an important etiologic factor... 

Fig. 14.6a,b. Female, 8 years old urge incontinence, UTI, unstable bladder, bladder ultrasound, a Full bladder, minor bladder trabeculation, bladder neck closed, b Uninhibited detrusor contractions with bladder neck opening and filling the posterior urethra up to contracted external sphincter with urine (arrow)... 

Radiographically uninhibited detrusor contractions are manifested by a small or moderate amount of contrast agent flowing into the posterior urethra, where it is stopped above the pelvic floor by either a reflexive contraction of the external sphincter or a static distal sphincter obstruction (Mundy et al. 1985) (Fig. 16.6). 

In contractile bladders (hyperreflexive detrusor), uninhibited detrusor contractions lead to a sudden bladder-neck opening in a formerly normally configured bladder base, with bulging of the posterior urethra up to the contracted external sphincter. This VCU finding is the manifestation of sphincter detru-... 

Fig. 16.7a,b. Male, 4 years old. Lumbar myelomeningocele, contractile detrusor VCU. a Closed bladder neck during bladder filling, bladder trabeculation, and sacculation, b Uninhibited detrusor contractions, massive back-up flow of contrast infusion contrast filled bulging bladder neck (arrow) up to contracted external sphincter (sphincter detrusor dyssynergia), some leakage around the catheter... 

Filling cystometry provides information on bladder capacity, detrusor contractility, and the presence of uninhibited bladder contractions, which could also cause LUTS... 

Especially in younger children, uninhibited and unpredictable detrusor contractions can be caused by constipation alone, by lower urinary tract infections (UTIs), or by constipation-associated UTls (Yazbeck et ak, 1987 Reiner, 1995). Pediatric pelvic organ structural immaturity prevents complete bladder filling by colorectal obstipation and hyperdistention. By contrast, mature vaginal-uterine or prostatic structural... 

Unstable bladder or detrusor instability, characterised by uninhibited, unstable contractions of the detrusor which may be of unknown aetiology or secondary to an upper motor neuron lesion or bladder neck obstruction. 

A slightly modified VCU technique allows the diagnosis of (uninhibited) unstable detrusor contractions and therefore the diagnosis of unstable bladder with accuracy similar to that of urodynamic techniques (sensitivity 93%, specificity 90.7%) (Potter et al. 1986). 

In patients with conditions characterized by involuntary bladder contractions, oxybutynin increases vesical capacity, diminishes frequency of uninhibited contractions of the detrusor muscle, and delays initial desire to void. Oxybutynin thus decreases urgency and the frequency of incontinent episodes and voluntary urination. 

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