Source: Dr Siow Woei Yun speaking at a seminar organised for GPs by SFCS on 26 June 2010.
Authors: Dr Siow Woei Yun, Consultant Urologist, Raffles Hospital.

Urinary incontinence (UI) is a common and distressing problem, which may have a profound impact on the patients’ quality of life (QoL). It is defined as any involuntary leakage of urine and almost always results from an underlying treatable medical condition. This article is concerned with the discussion of two types of UI, namely overactive bladder (OAB) and stress urinary incontinence (SUI).


The International Continence Society (ICS) defi nes overactive bladder (OAB) as a symptom syndrome consisting of “urgency, with or without urgency incontinence, usually with frequency and nocturia”. This collection of symptoms is suggestive of bladder overactivity (i.e. urodynamically demonstrable involuntary bladder contractions) but can be related to other forms of voiding or urinary dysfunction. Finally infection or other obvious pathology must be ruled out.

OAB Symptoms

  • Urgency: The complaint of a sudden, compelling desire to pass urine that is difficult to defer.
  • Urgency incontinence: The complaint of involuntary leakage of urine accompanied or immediately preceded by urgency.
  • Frequency: Voiding more than eight times in 24 hours and is the complaint by the patient who considers that he/she voids too often by day.
  • Nocturia: Usually accompanies urgency with or without urge incontinence and is the complaint that the individual has to wake at night one or more times to void.

A number of studies have reported that OAB affects 16% to 17% of the population worldwide yet despite these high prevalence rates, OAB remains underdiagnosed and undertreated. In fact, a population-based survey of 5500 females (aged ≥ 18 years) from 11 Asian countries found that while more than half of respondents suffered from OAB, only 21% sought treatment. As a result of social stigmas and the belief that UI is a normal part of aging, many patients are reluctant to seek medical help for OAB and UI.

Detrusor overactivity, or the occurrence of involuntary bladder contractions during the filling phase of a urodynamic study, may have several causes. Idiopathic detrusor overactivity is the most common type; however, overactivity might also be due to unrecognised neurogenic dysfunction or pathologies which include, for example urinary tract infection or urolithiasis. Haematuria in the presence of OAB symptoms must be investigated to rule out other pathology or malignancy (e.g. urothelial carcinoma in situ).


Clinical diagnosis is based on patient history, urine analysis and culture. Clinical workup can be supplemented with the use of a 24-hour bladder diary. Hospital-based investigations include intravenous urogram (IVU) or scope with or without cytology.


First-line therapy for the management of OAB is behavioral modification, including fluid management, bladder training and pelvic floor or Kegel exercises (PFEs). For instance, signifi cant improvements in urgency, frequency and nocturia can be achieved if patients decrease their fluid intake by 25%. Bladder training is effective in that it helps patients regain control of their bladder by teaching them to resist the urge to pass urine; however, this technique requires a high degree of motivation and commitment from patients. Pelvic floor muscle contractions help to suppress detrusor contraction and close the bladder outlet to prevent UI.

Antimuscarinic agents are the mainstay of pharmacologic therapy for OAB, targeting the muscarinic receptor family which comprises five subtypes. Of these symptoms, M2 and M3 are located in the bladder. In the normal state, M3 is the main receptor thought to be responsible for mediating bladder contraction.

A number of drugs are available with proven effectiveness including oxybutynin, imipramine, propiverine, trospium, tolterodine and solifenacin. Differences in efficacy, tolerability and safety may allow for some differentiation but a lack of head-to-head studies in most cases limits direct comparisons among drugs. The differences that do exist may be related to a variety of factors including metabolism, excretion, local effects, polarity and muscarinic receptor selectivity. Solifenacin, for example, In particular, solifenacin, an M3-selective anti-muscarinic, was recently introduced in Singapore. (see inset).


  • As early as Day 3, solifenacin (5 mg) shows an improvement in urgency control compared to placebo
  • Solifenacin shows greater improvements than tolterodine across all symptoms of OAB at 12 weeks
  • Solifenacin shows an improvement in residual urgency after ≥four weeks of therapy with tolterodine
  • Adverse events are mild to moderate in nature and result in low withdrawal rates.

Despite the effectiveness of these agents, patient compliance remains low. Therefore, a combination of patient education, behavioral interventions, and sideeffect management may allow patients to achieve more satisfactory outcomes with OAB therapy and improve compliance. Ideally, behavioural and newer pharmacologic therapies should be used in combination.

Minimally Invasive Therapy

Intravesical injection of botulinum toxin or sacral nerve modulation serve as alternatives to antimuscarinic therapy. Surgical intervention such as augmentation cystoplasty is used to increase bladder volume using a bowel segment, resulting in decreased urgency, UI and frequency. Since all surgeries carry inherent risks, such procedures should be reserved for cases in which conservative treatments have failed.

Stress Urinary Incontinence (SUI)

The prevalence of SUI varies from study to study but usually falls within the range of 5% to 30% of women (aged 30 to 60 years). Similar to OAB, SUI has a major impact on the QoL for many women. A number of factors may weaken pelvic floor muscles that support the bladder and urethra leading to the development of SUI. These include pregnancy, childbirth/delivery, age, menopause, manual labour, obesity and previous surgery. Malfunction of the urethral sphincter may also contribute to SUI.

Diagnosis and Treatment

Clinical diagnosis includes patient history (voiding, medical/ surgical, and current medications) and physical examination (abdominal, pelvic and rectal) to assess pelvic relaxation or prolapse. Biochemical investigations include urinalysis, urine culture and sensitivity, renal function and fasting blood glucose. Other investigations include urodynamic studies (with or without video), X-rays and cystoscopy.

Although PFEs serve to strengthen the pelvic floor and sphincter leading to an improvement of between 30% and 90%, surgery remains the main curative option for SUI with comparatively higher cure-rates. The previous “gold standard” of SUI surgical treatments, the Burch colposuspension, has success rates between 70% and 90% after five years of follow-up. The tension-free vaginal tape (TVT) procedure similarly achieves a high rate of long-term success in more than 86% of patients. More recently, the mini-sling procedures such as MiniArc have seen success rates exceeding 90%.

Mixed Urinary Incontinence

Briefly, mixed urinary incontinence is a combination of urgency urinary incontinence and SUI. Being more complex than the individual components, MUI requires a complete urological evaluation and simultaneous treatment of both conditions.


OAB and SUI are prevalent conditions that are currently underdiagnosed and therefore undertreated. In the case of OAB, effective management can be achieved with both non-pharmacological and pharmacological therapies. While evidence to-date indicates that antimuscarinics are effi cacious and well-tolerated, their side-effect profile limits their use in some patients. Newly introduced pharmacologic therapies provide an ever-increasing number of options available to the patient. With respect to SUI, PFEs are an option for the management although surgery is currently the curative treatment modality. In recent years, surgeries have evolved and have become less invasive. Since both of these conditions significantly impact the patients QoL, patient input on the effectiveness of various therapies is critical in identifying the best treatment option.