Functional: Overactive Bladder

See 2017 CUA OAB Guideline Notes

Terminology and definitions

• Definition of urgency: the complaint of a sudden compelling desire to void that is difficult to defer
• Definition of urgency urinary incontinence (UUI): involuntary leakage of urine, accompanied or immediately preceded by urgency
• Definition of increased daytime frequency: subjective complaint by the patient who considers that he or she voids too often by day
• Definition of nocturia: the complaint that the individual has to wake at night one or more times to void
• Definition of OAB: urinary urgency, with or without urgency incontinence, usually with increased daytime frequency and nocturia, in the absence of infection or other obvious pathology.
  • OAB is a symptomatic diagnosis and is distinct from detrusor overactivity, which is a urodynamic observation.
  • OAB can coexist with stress urinary incontinence (SUI).
• Definition of mixed urinary incontinence (MUI): involuntary leakage associated with urgency and with exertion, effort, sneezing, or coughing.
  • Thus in MUI, both SUI and urgency incontinence (“OAB wet”) are present in the same person. A person with SUI and “OAB dry” does not have MUI

Pathophysiology

• No animal model of OAB because reporting of subjective symptoms in animals is not possible
• 3 hypothesis: neurogenic vs. myogenic vs. integrative
  • Neurogenic hypothesis
    • Suggests that DO arises from generalized, nerve-mediated excitation of the detrusor muscle.
      • Nerve-mediated detrusor excitation is normal during voiding, where it is associated synergically with relaxation of the bladder outlet.
      • Nerve-mediated detrusor excitation should not occur during urine storage because of inhibitory influences within the CNS.
        • Emergence of inappropriate excitation during storage implies:
          • Loss of inhibition
          • Re-emergence of primitive spinal bladder reflexes
          • Acquisition of new reflexes
          • Sensitization of afferents.
  • Myogenic hypothesis
    • Suggests that overactive detrusor contractions result from a combination of an increased likelihood of spontaneous excitation within the smooth muscle of the bladder and enhanced propagation of this activity to affect an excessive proportion of the bladder wall
  • Integrative hypothesis
    • Suggests that a range of triggers can generate localized detrusor contractions, which can spread in the bladder wall through various routes of propagation. Consequently, urgency is a result of distortions in the bladder wall, and it is associated with urodynamic DO if the contractions spread to a sufficient proportion of the bladder wall
• Aging, neurologic disease, female gender, bladder outlet obstruction, and metabolic disease are potential influences on OAB etiology

Prevalence and costs

• Prevalence 12%
  • EPIC study
    • Design: population-based, cross-sectional telephone survey of adults aged ≥18 years in 5 countries and used the standardized ICS definition of OAB
• Both genders have similar rates of OAB, but men have a higher prevalence of “OAB dry” whereas woman have a higher prevalence of “OAB wet”
  • The difference in the prevalence of incontinence may be a result of the relative weakness of the bladder neck and the urethral sphincter  mechanism in women
• Storage LUTS have a greater impact on health-related quality of life than other LUTS

Diagnosis and Evaluation

• Mandatory by 2017 CUA OAB Guidelines (4): H+P, U/A, questionnaire, voiding diary
• History and Physical Exam
  • History
    • Characterize LUTS (presence or absence, incidence, severity, bother, and effect on quality of life for each of the OAB symptoms (urgency, urgency incontinence, increased daytime frequency, and nocturia).
      • Patients with urgency tend to describe frequent voids with a low typical voided volume.
      • Nocturia is somewhat variable in OAB.
      • Voiding and postmicturition LUTS, dysuria, hematuria, and LUT pain should also be assessed.
    • Nature and volume of fluid intake, recognizing that stimulants and polydipsia affect LUTS, and that patients may adapt their intake to reduce the impact of symptoms.
    • Whether occult neurologic disease could be present; for example, recent onset of OAB with symptoms of erectile dysfunction or tremor.
    • Obstetric and gynecologic history, previous surgery and/or radiotherapy, bowel symptoms, and medication history.
    • Other medical issues (e.g., contraindications to antimuscarinic therapy (see Pharmacological Managments of LUTS Chapter Notes)
  • Physical Exam
    • Abdominal and pelvic examination, general examination (e.g., peripheral edema), and basic neurologic examination.
    • Assessment of bladder emptying is necessary (most simply by palpating the lower abdomen if the patient is slim).
• Labs
  • Urinalysis
    • Important in all patients to exclude urinary tract infection, hematuria, and leukocyturia.
• Other
  • Questionnaire
    • The most time-efficient and systematic way to explore contributory LUTS is to use a symptom assessment questionnaire.
  • Frequency volume chart
    • Remains the principal method for evaluating frequency and nocturia in an objective way.

Differential Diagnosis

• Definition of bladder pain syndrome (BPS): complaint of suprapubic pain related to bladder filling, accompanied by other symptoms such as increased daytime and nighttime frequency, in the absence of proven urinary infection or other obvious pathology.
  • The urgency of OAB characteristically does not include pain; where pain causing urgency is reported, it is categorized as BPS.
    • Differences that help to distinguish BPS include:
      1. Painful nature of symptoms
      2. Steady increase in pain with filling
      3. More consistent voided volumes compared with OAB
      4. Ability to defer voiding

Initial treatment outline

• See 2017 CUA OAB Guideline Notes
• Options:
  1. Observation
  2. Conservative
  3. Pharmacological
  4. Surgical

• • Observation
    • After assessment has been performed to exclude conditions requiring treatment and counseling, “no treatment” is an acceptable choice made by some patient
  • Conservative:
    • Weight loss
    • Smoking cessation
    • Diet modification (decreased use of caffeine, decreased fluid intake, decreased alcohol intake, changes in food and drink
    • Pelvic floor muscle training, to resist and occasionally to terminate overactivity when it arises
    • Bladder retraining to encourage inhibitory influences on the lower urinary tract
      • These treatments need to be attempted for at least 6 weeks to obtain benefit, and they should ideally be tried for 3 months.
  • Pharmacological
    • If conservative treatment fails, the patient can then be offered antimuscarinic therapy if there are no contraindications.
      • At least 2 antimuscarinics must be tried for at least 4 weeks each, starting at a low dose and building up to a maximum dose.
        • Incidence of acute urinary retention in men receiving antimuscarinics with or without an α1-adrenergic blocker is up to 3%.
      • If patients are unable to tolerate antimuscarinics or the antimuscarinics have failed to control symptoms, then patients can be prescribed mirabegron.
  • Surgical
    • If conservative and medical therapies fail to control symptoms and the patient requires further treatment, invasive urodynamics is then performed to confirm DO and/or detrusor overactivity incontinence, and minimally invasive surgery, where indicated and available is offered.
    • Options:
      • Intradetrusor injections of botulinum toxin-A
      • Percutaneous sacral nerve stimulation
      • Percutaneous tibial nerve stimulation.
      • Other options include augmentation cystoplasty, in its various forms, or an ileal conduit with or without a subtotal cystectomy. In adults, augmentation is no longer recommended for the treatment of detrusor overactivity because the long-term success of this procedure is not high.

Specialized evaluation and management outline

• Altered drug dose, different agent, or combination therapy may achieve sufficient improvement to obviate the need to consider more invasive investigation and treatment.
• Urodynamic evaluation should be considered where conservative and drug therapy fails adequately to manage OAB in a patient who is sufficiently healthy and who is considering more invasive therapeutic interventions. The primary aim of urodynamic studies is to reproduce the patient’s symptoms and to identify additional factors likely to influence management decisions.
  • The two main urodynamic diagnoses associated with OAB are DO and increased filling sensation.
    • Note that some patients with DO are asymptomatic (i.e., they do not experience OAB).
    • DO may not be present in some patients with OAB, especially in women

References

• Wein AJ, Kavoussi LR, Partin AW, Peters CA (eds): CAMPBELL-WALSH UROLOGY, ed 11. Philadelphia, Elsevier, 2015, chap 76