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The idiopathic overactive bladder (OAB) is a clinically-diagnosed symptom complex, consisting of frequency, urgency and nocturia with or without urge-associated urinary incontinence. This complex assumes no underlying cause as a source of bladder dysfunction. The alternate term of ‘detrusor overactivity’, on the other hand, is a urodynamic diagnosis based on cystometrography (CMG) — previously termed ‘bladder instability’ — which is characterised by an unprovoked rise in detrusor pressure during the filling phase of a CMG, and is often associated with a clinical feeling of urgency in a normally sensate individual.
There have been a number of challenges in determining what is defined by ‘normal’ and the International Continence Society (ICS) now suggests that clinical deterioration is what is perceived by the patient and leads them to seek medical help. In addition to ‘normal’ voiding patterns during the day, the ICS has qualified this as a “sudden and compelling desire to pass urine, which cannot be deferred” and may lead to urinary incontinence.
Epidemiological studies have found that the prevalence of this condition is rising, and it now affects approximately 16 per cent of European and American populations. Of course, not everyone presenting with these symptoms has a diagnosis of OAB made, and there are a number of conditions that need to be excluded prior to diagnosis including, but not limited to, urinary tract infections (UTIs); bladder tumours/calculi; pelvic organ prolapse; prior pelvic surgery; neurological lesions; excessive fluid intake; pregnancy; diabetes; and behavioural issues, such as anxiety and habit.
In the paediatric population, much of the symptomatology is difficult to elicit directly from patients and one must rely to a certain extent on the history presented by a parent/legal guardian. The definitions remain broadly similar to the adult population, however, children broadly fall into four categories when dealing with voiding dysfunction:
Voiding dysfunction with or without constipation (bladder bowel dysfunction).
Congenital structural anomalies (ectopic ureter leading to continual incontinence).
By far the most common of these is the first category of voiding dysfunction with/without constipation. However, the most feared is the accurate diagnosis and management of the neurogenic bladder.
Broadly speaking, this spectrum of conditions can be categorised into open or occult neural tube defects (NTD), sacral agenesis, spinal cord lesions and cerebral palsy.
Open NTDs can be subcategorised into (lipo) myelomeningocoele (exposed meninges and neural tissue +/- lipoma of the cord), and meningocoele (exposed meninges only). These are thought to affect 1/1,000 births and rates vary in different geographic regions, with access to prenatal ultrasonographic scanning and differing legislation determining termination. They affect the lumbosacral/sacral regions of the cord in approximately 67 per cent of patients and are usually closed as a neonate. Interestingly, the severity of symptom complex cannot be predicted as easily as that of a spinal cord injury; however, as a rule of thumb, the higher the lesion, the more likely the degree of severity. Management of these conditions involve initial urodynamic studies and long-term follow up for vesicoureteral reflux, incontinence and upper-tract deterioration. Those patients with associated detrusor-sphincter dyssynergia (DSD) are more likely to develop poor bladder compliance and worsening upper tracts. Bowel management is also especially important in this cohort. In adolescence and adulthood, management of erections, sexual function and fertility prove a challenging but important facet to their care.
Occult NTDs and spinal cord tethering (due to lipomeningocoele, intradural lipoma, dermoid cysts/sinuses, tight filum terminale) often do not present clinically until patients demonstrate a failure to achieve continence. Urodynamic studies may demonstrate lower-tract dysfunction, such as large capacity, and poorly-emptying bladders with associated poor sphincter functions. Neurosurgical correction has been shown to improve outcomes in this cohort, however, there is a paucity of prospective data in this cohort. Sacral agenesis (associated with maternal diabetes mellitus) can be associated with a wide range of neurologic deficits associated with voiding dysfunction, and just over one-third will demonstrate evidence of poor compliance and increased bladder-filling pressures on urodynamic studies.
Spinal cord injuries are usually associated with a period of spinal shock lasting at least six weeks post-injury, and therefore it is advisable to defer urodynamic testing until after this period. Sacral lesions are usually associated with safe, compliant, low-pressure bladders that fail to empty completely and are associated with poor sphincter function and therefore incontinence.
Suprasacral injuries, on the other hand, may be associated with DSD, poorly-emptying bladders with poor compliance, which have a higher incidence of upper-tract deterioration. Care must be given to bowel management in both groups and caution is relayed to the latter group, especially with injuries above thoracic level 6 (T6) due to the concomitant issue of autonomic dysreflexia, which may be triggered endogenously or iatrogenically.
Cerebral palsy is thought to be due in part as a result of a non-progressive perinatal insult. Urodynamic testing in this cohort will yield detrusor overactivity in approximately 80 per cent of patients, of which 5 per cent will demonstrate DSD. Continued urodynamic testing is not required and most regain some degree of continence, however functional impairment, intellectual disability and fluid intake remain important considerations.
Non-neurogenic voiding dysfunction
This is by far one of the most common reasons for referral to the paediatric urology clinic. Children are usually referred via one or both of the following symptom complexes:
Storage lower urinary tract symptoms, with or without daytime incontinence, as well as commonly having nocturnal enuresis.
Recurrent, non-proven UTIs, which may demonstrate some abnormalities on urinalysis, or symptoms of cystitis.
The most important part of the consultation will lie in an accurate establishment of the history. Symptoms may be long-standing and parents may have been to see their family doctor and/or paediatrician on a number of occasions before being referred for urological management.
It is important to elucidate the following from the history:
Duration of symptoms.
Exact symptom profile (nature of symptoms of cystitis/UTI, presence of pyrexia, whether they are primary or secondary).
Age at toilet training.
Family history of similar symptoms (sibling/parent).
Whether symptoms are worse at home or at school.
Presence of anxiety due to a life event (school, parental separation, family death).
How the child voids in the bathroom (especially important for girls).
Tendency to be distracted by other activities (TV, games, etc).
Tendency to hold on to urine for periods of time, followed by urgency.
History of constipation (Bristol Stool Chart important; Figure 1).
The importance of correct toileting position is usually under-appreciated by physicians and families alike. Children should be sat on the toilet — after completely removing underwear — with a foot stool under the feet (see Figure 2). The correct angle is less than 45 degrees, with the legs partially spread. This allows the urogenital diaphragm to be completely relaxed with an open relaxed pelvis, and open anorectal angle, and no pressure on the puborectalis muscle.
On physical examination, it is important to ensure that the abdomen is normal, with a non-palpable bladder. Lower-back examination should be performed to rule out the presence of abnormal hair tufts, sacral dimples, or lumbosacral defects. In boys, the phallus and testes must be examined to ensure a good orthotopic position, with a normal consistency. In girls — with the aid of a chaperone — the vaginal introitus must be inspected to exclude the presence of labial fusion as a cause for symptoms.
Monosymptomatic nocturnal enuresis is a common condition in the paediatric population, with a prevalence of approximately 10 per cent of five-year-olds, reducing to 5 per cent of 10-year-olds, and up to 1 per cent of 16-year-olds. There is a regression rate of approximately 15 per cent per annum, with siblings of those affected at a much higher risk of approximately 30-to-40 per cent incidence. Theories include derangements of antidiuretic hormone (ADH) circadian rhythms, DSD, attention deficit hyperactivity disorder (ADHD), and very commonly, simple failure of arousal, which is often at a higher prevalence in those with an intellectual disorder. Treatment involves timed voids, bell-pad alarms and in some cases, vasopressin analogues (desmopressin). However, when this condition is associated with daytime symptoms, it is no longer monosymptomatic and must be taken in conjunction with voiding dysfunction in general.
Children with voiding dysfunction often exhibit Hinman-type behaviour, categorised by voiding postponement, including somatic gating mechanisms such as the eponymous Vincent’s Curtsy or squatting (to increase pressure on the perineum) (Figure 3). The result of these manoeuvres leads to initially sudden urgency and long voids to completion at a later time, followed by the development of idiopathic-acquired detrusor sphincter dyssynergia with a loss of afferent bladder sensation on filling with smaller, staccato voids and frequency. This may be associated with the development of symptoms of cystitis. On urodynamic testing, a significant proportion of patients will eventually develop detrusor overactivity, and a proportion may develop poor compliance and secondary vesicoureteral reflux. A small proportion may also progress to renal failure. The vast majority of children in this cohort will also exhibit a history of constipation, or prior treatment for constipation. The presence of a full rectum puts pressure on the bladder neck and makes it difficult to voluntarily void. This leads to the development of a symptom cycle, ultimately resulting in a ‘non-neuropathic, neuropathic’ bladder, or in modern terminology, ‘bladder bowel dysfunction’.
The management of this condition is tailored to each patient and is multimodal, but not necessarily pharmacological, in nature, whilst the natural history of this condition tends towards resolution by late adolescence/early adulthood. The aim of the paediatric urologist/family doctor is to improve symptoms and reduce the risk of irreversible urinary tract damage by this stage.
Goals of treatment include:
Parental and patient education to explain the aetiology, natural history and outcomes from this disease, and to explore and deal with their underlying ideas and expectations prior to consultation. Many parents expect an immediate pharmacological/surgical end-point to this condition and the consultation can be challenging.
Explore any recent stressors and/or life events in the household. Psychological input has been shown to be of benefit in select cases.
Emphasise the paradoxical importance of good hydration and to treat constipation with or without over-the-counter, fibre-based laxatives to ensure a Bristol 4 stool every day.
Emphasise the importance of timed/chronological voids where the patient does not void based on their own sensation.
Stress the importance of good toileting habits and voiding/stooling positions.
Ensure that schools are aware of the importance of regular voiding. Letters may need to be given to the patient, addressed to the school, outlining this. Vibrating alarm watches may also be useful to remind children when to void.
Follow-up should be with a voiding/stooling calendar and a uroflow with electromyography (topical sensor electrodes placed on the perineum) can be useful to assess response, gauge flow rates and voiding efficiencies, as well as the continued presence of DSD. Any symptoms suggestive of cystitis/UTI must be accompanied with a urine sample for microscopy and culture, and not just urinalysis.
If these measures fail to work, biofeedback carried out by urology nurse specialists has been shown to improve identification of bladder-filling sensation and improved sphincter relaxation during voiding. If symptoms have improved, but the patient still demonstrates evidence of bladder over-activity despite excellent compliance and re-investigation, then pharmacological treatment in the form of an antimuscarinic or beta-3 adrenoceptor agonist may be considered following careful counselling regarding side-effect profiles. Of these treatments, arguably the most important is the avoidance of constipation and maintenance of good hydration.
There are a number of conditions which can mimic detrusor overactivity in the adult population, many of which generally do not apply to a paediatric cohort. It is important to realise, however, that children represent a very different cohort of patients, with their own distinct aetiologies. It is vitally important to rule out an underlying neurogenic/congenital structural abnormality when dealing with voiding dysfunction and during treatment of the latter, pharmacological/surgical treatments appear much further down the list of potential treatments than in a similar adult population.
References on request