Overactive Bladder
Sharon Yeo
Introduction
Overactive bladder (OAB) is a common condition presenting to the general practitioner and
urologist. It has a considerable impact on patients’ quality of life (QoL) and is of significant
economic cost.1
Definitions
Overactive bladder is characterized by the storage symptoms of urgency with or without
urgency incontinence, usually with frequency and nocturia. This is in the absence of proven
infection or other obvious pathology.2 OAB is a symptomatic diagnosis.
Urgency is the hallmark and most significant symptom of OAB, and is the complaint of a
sudden compelling desire to void that is difficult to deter.2 Patients complain of the associated
“fear of leakage” and this is often the reason they seek treatment.
Urgency incontinence, defined as the involuntary leakage of urine, accompanied or
immediately preceded by urgency,2 occurs in some OAB patients and may lead to social or
hygienic problem, resulting is a poor QoL.
Detrusor overactivity (DO) is a urodynamic diagnosis, characterized by involuntary
detrusor contractions during the filling phase, which may be spontaneous or provoked. DO is
divided into idiopathic or neurogenic, depending whether there is an underlying neurologic
cause.
Pathophysiology and Etiology
Urine storage and voiding functions of the lower urinary tract are the result of complex
interactions with the nervous system. Overactive bladder may be caused by conditions
ranging from decreased central inhibition to over-sensitisation of the bladder.3-5 Treatments
are aimed at alleviating symptoms, and improving QoL.
Clinical Assessment
Clinical history
An accurate and detailed history from the patient is essential. It should include any frequency,
urgency, nocturia, urgency or stress incontinence, or both. Neurological conditions, obstetric
and gynaecological history, previous surgeries, spinal procedures, other lower urinary tract
symptoms (LUTS), bowel symptoms and sexual function should be noted as are
comorbidities and medication history. Adequate time should be set aside for taking a detailed
history and insight into the patient’s symptom severity and QoL, which is important in
making management decisions in OAB. Many patients cope by wearing pads especially
when going out, and they may limit their fluid intake or even restrict activities for fear of
embarrassing leaks.
Bladder cancer and carcinoma-in-situ (CIS), can cause similar symptoms of urgency and
frequency. Past history of bladder cancer/CIS, cigarette smoking and presence of gross
haematuria are suspicious features. Such patients, together with those who have voiding
difficulties or suspected neurological disease are considered complicated cases and early
specialist referral is warranted.6 Urinary tract infection (UTI) should also be excluded with
questions about dysuria, foul-smelling urine.
OAB can coexist with stress urinary incontinence (SUI) in both men and women.
Management will be based on predominant symptom and individualized, starting from
conservative to invasive options.6 Relevant history would be obstetric history in women,
especially prolonged second stage of delivery, use of instrumentation, birth of large babies
and perineal tears. In men, previous radical prostatectomy or transurethral resection of
prostate (TURP) may predispose to SUI.
Physical examination
Targeted physical examination including a digital rectal examination in men to estimate
prostate size, evaluate anal tone and perineal sensation can help to determine the cause of
urinary symptoms. Physical examination in women should include a vaginal examination
with attention to presence of genitourinary prolapse, oestrogen status and strength of pelvic
floor muscle contraction. The patient should be asked to cough in an attempt to demonstrate
any co-existing SUI.
Evaluation tools
In OAB, diagnosis and treatment are largely based on patient’s reported symptoms. Many
international questionnaires have been developed to assess the symptom severity, QoL and to
provide more objective means to monitor treatment outcomes with symptom scores.
Bladder diary is a patient’s own recording of his/her daily voided volumes and times of
micturitions, episodes of leakages, pad usage, degree of urgency, and fluid intake, typically
done over three to seven days. This helps to gauge symptom severity. Repeating bladder
diary at intervals is useful in monitoring treatment response. In many patients, doing a
bladder diary has a therapeutic effect and increases their sense of control in their own
management. It is also a good tool for doctors to predict which patients will likely be
compliant to a treatment programme.
Investigations
Baseline investigations in OAB include urinalysis (dipstick) of a mid-stream urine specimen
to exclude UTI and any symptomatic UTI should be treated appropriately. Presence of
protein, blood (microscopic haematuria) and glucose may indicate underlying renal disease,
malignancy or diabetes mellitus, respectively and would require appropriate specialist
referral.
Urodynamics studies (UDS) is not a baseline investigation and should not be routinely
carried out before conservative or medical treatment in OAB. It should only be considered
when those non-invasive options have failed and the patient is considering more invasive
treatments. UDS should aim to replicate the patient’s symptoms and direct management.
Management
Management of OAB begins with non-invasive, lifestyle interventions such as healthy
weight loss, fluid restriction, decreasing caffeine or alcohol intake and smoking cessation.
Bladder training is recommended together with other lifestyle interventions, involving
voiding according to a fixed schedule, or intervals. Increasing pelvic floor muscle contraction
strength and durability has been shown to inhibit detrusor contraction in OAB patients.7
Patients of both sexes can be taught proper techniques by professionals. Pelvic floor muscle
training can be augmented with biofeedback, weighted vaginal cones (in women), electrical
or magnetic stimulation of the nerve supplying the pelvic floor muscles.
Antimuscarinics are currently the mainstay of medical therapy in OAB. Acetylcholine is the
primary post-ganglionic neurotransmitter in the parasympathetic neurons. Acetylcholine
released from parasympathetic nerves activate muscarinic (predominantly M3) receptors in
the bladder, leading to detrusor contraction.8 Antimuscarinics available in the market differ in
their pharmacokinetic properties, lipid-solubility, formulations and receptor affinity and
specificity. These account for their differing side effects and efficacy. Well-recognized
potential side effects of this class of drugs are dry mouth and eyes, blurred vision,
constipation, voiding difficulties with retention of urine and cognitive impairment. Closedangle glaucoma is a contraindication to the use of this medication. Different antimuscarinic
agents may be tried to see which agent gives most symptom improvement with least side
effects. It is good clinical practice to offer early review of patient after commencing a new
drug to monitor efficacy and side effects.
Activation of the sympathetic system via β3- adrenoceptors causes relaxation of the detrusor
muscle during storage phase.9 A new medical therapy alternative, ß3- receptor agonist, has
now been approved for use in Japan, USA and in the UK for the treatment of urinary
frequency, urgency and urgency incontinence. It is reported to have similar efficacy with less
side-effects than current antimuscarinic agents.
Botulinum toxin is a neurotoxin produced by gram-positive Clostridium botulinum. It is an
acetylcholine release inhibitor, inhibiting the release of acetylcholine from presynaptic
cholinergic nerve terminals into the neuromuscular junction via disruption of specific sites on
SNARE proteins that form the synaptic fusion complex, thereby causing paralysis of muscles.
Botulinum toxin A has received FDA approval for use in the treatment of neurogenic detrusor
overactivity incontinence in adults who have failed or could not tolerate anticholinergic
medications. It is also increasingly being used in patients with idiopathic refractory urgency
urinary incontinence. The efficacy generally lasts for 6 to 9 month, with repeated injections
required. The main adverse effect is that of increased post-void residual volume requiring
clean intermittent catheterization (CIC), which patients should be counselled appropriately
prior procedure.
Posterior tibial nerve stimulation (PTNS) and sacral nerve stimulation (SNS) are
alternative treatments to patients who are refractory to conservative and medical therapy.
They involve electrical stimulation of sacral nerves, thereby believed to modulate the
micturition reflex and also have direct inhibitory effect on bladder to decrease pathological
detrusor contractions.
Lower urinary tract function involves complex interactions of multiple pathways with the
nervous systems. It is an area of intense research and many novel agents are being studied for
their clinical potential as pharmacological targets in OAB treatment.
Radical surgical option of bladder augmentation may be considered in carefully selected
patients if all other treatment fails. In addition to risks of major bowel surgery, serious
metabolic consequence can result and the late complication risk of malignancy. Such major
surgery is strictly reserved for patients with severe symptoms who have failed all other less
invasive treatments and is not commonly done.
Summary
Overactive bladder is a very prevalent condition with significant impact on quality of life.
OAB is a clinical diagnosis. Management begins with conservative lifestyle interventions,
behavioural therapies, and antimuscarinics is currently the mainstay of medical therapy. The
role of intravesical botulinum toxin injection is increasing. Radical surgery is reserved for
severe refractory cases and is rarely performed now.
References
1.
Irwin DE, Kopp ZS, Agatep B, et al. Worldwide prevalence estimates of lower urinary tract symptoms, overactive bladder,
urinary incontinence and bladder outlet obstruction. BJU Int 2011;108,1132-1139.
2.
Abrams P, Cardozo L, Fall M, et al. The Standardisation of Terminology of Lower Urinary Tract Function: Report from the
Standardisation Sub-committee of the International Continence Society. Neurourol Urodyn 2002;21(2):167-178.
3.
de Groat WC. A neurological basis for the overactive bladder. Urology 1997;50(6A Suppl.):36-52.
4.
Brading AF. A myogenic basis for the overactive bladder. Urology 1997;50(6A Suppl.):57-67.
5.
Drake MJ. The integrative physiology of the bladder. Ann R Coll Surg Engl 2007; 89: 580–585.
6.
Abrams P, Andersson KE, Birder L, et al. Fourth International Consultation on Incontinence Recommendations of the
International Scientific Committee: Evaluation and Treatment of Urinary Incontinence, Pelvic Organ Prolapse, and Fecal
Incontinence. Neurourol Urodyn 2010;29:213–240.
7.
Greer JA, Smith AL, Arya LA. Pelvic floor muscle training for urgency urinary incontinence in women: a systematic
review. Int Urogynecol J. 2012 Jun;23(6):687-97.
8.
Fetscher C, Fleichman M, Schmidt M, Krege S, Michel MC. M3 muscarinic receptors mediate contraction of human
urinary bladder. Br J Pharmacol. 2002;136:641-643.
9.
Yamaguchi O, Chapple CR. Beta3-Adrenoceptors in Urinary Bladder. Neurourol Urodyn, 2007;26(6):752-6.
Questions
1. OAB is a condition that only affects women.
A)
True
B)
False
2. Extensive investigations and tests are required to diagnosis OAB.
A)
True
B)
False
3. Urodynamics is a first-line investigation in the diagnosis of OAB.
A)
True
B)
False
4. Lifestyle modifications and pelvic floor exercises have no role in the management of
OAB.
A)
True
B)
False
5. Antimuscarinics have no adverse effects.
A)
True
B)
False
Answers
1. False
2. False
3. False
4. False
5. False