Urinary Incontinence (UI) - an involuntary leakage of urine which is more common in women than men.

Normal Micturition

Stress Incontinence

 

Definition: Leakage of urine associated with physical activity such as exercise, coughing or sneezing. The rise in intrabdominal pressure is transmitted to the bladder and causes pressure within the bladder to exceed pressure within the urethra so leakage of urine occurs. 

 

Pathophysiology:

Failure of continence is due to either urethral hypermobility or sphincter tone failure.

 

  • Urethral hypermobility: The pelvic floor consists of three layers that enable it to behave as a supporting structure:   
    1. Endopelvic fascia – this connects the viscera to the pelvis side wall 
    2. Levator ani and their facia – the vagina, urethra and rectum pass through this muscular  structure
    3. Perianal membrane / urogenital diaphragm – attaches vagina to ischiopubic ramus and provides support to the urethra.

     

    Normally, muscles of the pelvic floor contract to maintain continence, however a defect with this structure can lead to urethral hypermobility and stress incontinence.

     

     

    Image adapted from: Al-Hayek S, Abrams P. (2005). Stress incontinence: why it occurs. Women's health medicine. 2 (6), 26-28.

     

    A) Normally, contraction of pelvic floor muscles maintains continence. B) Loss of pelvic support due to weakened muscles results in loss of continence.

     

      • Sphincter tone failure

      Stress incontinence may also be due to failure of the urinary sphincter to contract efficiently, allowing urinary leakage.  

      Urge Incontinence

      Definition: This type of UI is accompanied by the desperate desire to urinate either before or during leakage. It may be triggered by changes in temperature, opening the front door (latchkey incontinece), the sound of running water or orgasm.

       

      Pathophysiology:

      This is caused by instability within the detrusor muscle leading to involuntary contractions. It is accompanied by involuntary relaxation of the urethra. This type of incontinence may be associated with conditions such as MS, Parkinson’s, dementia or spinal cord injury. Urge incontinence may also occur with inflammation of the bladder. Hence assessment for UTI is important.

      Overactive Bladder Syndrome

      Definition: This is urgency that may or may not be accompanied with urge incontinence. Over activity of the detrusor muscle is the cause of this type of incontinence. Women may also present with increase in frequency, nocturia and low voiding volumes.

       

      Pathophysiology

      Here, microscopic changes are seen within the cell structure of the bladder. Normally, the bladder is densely innervated, however in OAB patchy denervation occurs. Also seen as a microscopic change is an increase in connective tissue deposits between the muscle bundles and hypertrohpy of smooth muscle cells, which then form close junctions. This then leads to an increase in electrical coupling and a rise in the firing and generation of action potentials. There is an increase in excitability during the micturition reflex leading to a sense of urgency and involuntary contraction.

      Overflow Incontinence

      Definition: This is due to insufficient bladder emptying and continuous leakage of urine - the normal flow of urine is blocked and the bladder cannot empty properly. This may be due to faecal impaction, a tumour or benign prostatic hyperplasia in men.

       

      Mixed urinary incontinence is a combination of both stress and urge incontinence.

      Risk Factors

       

      It is important to take a thorough history as the symptoms of UI can vary and may overlap with other conditions

       

      History Taking

       

      When taking history it important to ask about impact on life - social/sexual and methods patient uses to manage UI.

       

      Examination

         

        • Abdominal examination. This may help identify an enlarged bladder or any masses.
        • Digital assessment of pelvic floor muscles – assess contraction and sensation
        • Vaginal examination – are there any signs of pelvic organ prolapse – this would require referral to a specialist. This is also to asses any masses, inflammation or irritation.
        • Rectal examination helps determine a posterior wall prolapse or constipation
        • Perineal sensation.
        • Consider an assessment of their cognitive status by taking the abbreviated mental test score – particularly in women over the age of 75.

         

          The presence of any of these symptoms indicates urgent referral.

           

          Red flags

          Management

          This will vary depending on the type incontinence involved, hence it is important to take a thorough history and examination.

           

          Stress incontinence

           

          Conservative management

          • Pelvic floor muscle training for at least three months consisting of at least eight contractions at least 3x/day
          • Electrical stimulation should be considered in women who cannot contract pelvic floor muscles.

           

          Medical Management

          • Duloxetine – this should only be offered as an alternative to surgical treatment. It should not otherwise be considered as first line therapy for stress incontinence. See table below for details.

           

          Surgical Management

          Surgical management aims to alter the structure of the lax bladder and urethra due to inadequate pelvic floor support.

          • Tension free Vaginal Tape- This is a relatively simple procedure. A mesh like tape passes through both sides of the endopelvic fascia and behaves as a sling.  It is placed around the urethra in order to create support without obstruction.
          • Colposuspension – the neck of the bladder is stitched and attached to the posterior pelvic wall stabilising the position of the bladder. The procedure also tenses the urethra making the leakage of urine more difficult.
          • Bulking agents – Collagen/Silicon/Teflon can be injected around the urethra to bulk the tissue. This creates a narrower passage for the flow of urine, which prevents leakage. On voluntary urination, tissue separates naturally. This procedure is better short term than long.

          Urge Incontinence/Overactive bladder syndrome

           

          Conservative management

          • Bladder training – timed voiding.
          • Modification of fluid intake
          • Women with BMI > 30 advised to lose weight.

           

          Medical management

          • First line – oxybutynin. If this is not well tolerated consider darifenacin, solifenacin or tolterodine. See table below.
          • Propiverine for treatment of frequency
          • Desmopressin to reduce nocturia.

           

          Surgical Management

          • Augmentation cystoplasty – bowel is used to increase the volume of the bladder and create a low pressure reservoir. The bowel is usually attached at the top of the bladder.
          • Urinary Diversion
          • Sacral nerve stimulation – a device is implanted in the buttocks that stimulates the sacral nerves. The lead is placed in the sacrum and connects to the nerves and the implant in the  buttocks. This procedure must first be tested to see if sacral nerve stimulation is beneficial to the patient – a temporary test electrode is placed in the one of the sacral nerves to see if this stimulates bladder function. If so, the procedure can then be carried out.

          Overflow incontinence

          • Treatment involves the removal of blockage. A catheter may also be used as a method of treatment.  

          Mixed Incontinence

          • Assessment should be made as to whether stress or urgency symptoms dominate. Treatment should then be tailored to this

          Parasympathetic cholinergic nerves innervate the bladder and act via muscarinc receptors, particularly M3 receptors. Contraction of the detrusor is mediated by acetylcholine – antagonism of the muscarinic receptors is the target of many of the drugs used in the treatment of incontinence mentioned above.

           

           

          N.B The need for continued anti-muscarinic therapy should be assessed after 3-6 months.

          Bibliography and Suggested Reading

          Al-Hayek S, Abrams P. (2005). Stress incontinence: why it occurs. WOMEN’S HEALTH MEDICINE. 2 (6), 26-28.

          Declan P. Keane, Suzanne O'Sullivan. (2000). Urinary incontinence: anatomy, physiology. BaillieÁ re's Clinical Obstetrics and Gynaecology. 14 (2), 207-226.

          William D. Steers. (2002). Pathophysiology of Overactive Bladder and Urge Urinary Incontinence. REVIEWS IN UROLOGY. 4 (4), S7-S18.

          Edward J. McGuire. (2004). Pathophysiology of Stress Incontinence. REVIEWS IN UROLOGY. 6 (5), S11-S17.

          Cathy Allen, Declan Keane. (2005). Pathophysiology of urinary incontinence. Reviews in Gynaecological Practice. 5 (1), 65-70.

          John O. L. DeLancey. (1997). The pathophysiology of stress urinary incontinence in women and its implications for surgical treatment. World J Urol. 15 (5), 268-274.

          John O. L. DeLancey. (1997). The pathophysiology of stress urinary incontinence in women and its implications for surgical treatment. World J Urol. 15 (5), 268-274.

          Dweyer, N T. (2006). Stress Urinary Incontience in Women. UROLOGY (Urology Board Review Manual). 13 (1), 1-12.

          NICE guidlines on management of Urinary Incontinence

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