About UAB

The underactive bladder

Patients with an underactive bladder are unable to produce an effective voiding (emptying) contraction. This is sometimes referred to as voiding difficulty. The International Continence Society refers to the condition of detrusor under activity, defined as a contraction of reduced strength and/or duration, resulting in prolonged bladder emptying and/or failure to achieve complete bladder emptying within a usual time span. It is characterized by the loss of usual sensation of the bladder filling and failure of the detrusor muscle to contract as forcefully as it should, resulting in incomplete bladder emptying. This condition has also been referred to as a hypotonic or flaccid bladder or detrusor hypoactivity. The prevalence of underactive bladder
remains unknown.

Symptoms include
  • Frequency
  • Incomplete bladder emptying
  • Incontinence
  • Urgency
  • Recurrent Urinary Tract Infections

    A symptom of voiding difficulty is the complete inability to void a full bladder. Other symptoms caused by voiding difficulty may be incontinence leading to skin problems and recurrent urinary tract infections (UTIs). Some patients describe the need to 'double void'.


    Common causes of underactive bladder

    The most common causes of detrusor underactivity can be classified as:

    Neurological

    Damage to the peripheral nerves of the bladder or the lower spinal cord may cause the sensation of bladder filling to be absent or reduced, and the bladder is emptied by frequent voiding of small amounts of urine. Large residual volumes may accumulate (500-2,000ml), which are associated with difficulty in emptying the bladder and overflow urinary incontinence.

    Patients with spinal cord lesions frequently present with lack of detrusor-sphincter synergy and it is a particular feature of voiding difficulties in older people following CVA. Normal voiding also relies on a synergy between the bladder contracting and the bladder neck opening. When this is interrupted, the patient will experience constant urinary urge due to detrusor contraction and inability to relax the internal sphincter. The result is incomplete bladder emptying with significant residual volumes and urge incontinence.

    Suprapontine lesions usually result in detrusor areflexia (a non-contractile bladder). The bladder fails to empty because it has little muscular activity and assisted voiding may take place by
    straining. The patient may present with symptoms of incomplete bladder emptying, frequency and urgency, but on further examination there is a poor flow rate and often a significant post-void residual urine volume.

    Myogenic

    With parasympathetic nerve stimulation the muscarinic receptors in the bladder should contract. Following an epidural this muscle activity may be absent or reduced, leading to acute retention of urine and insidious voiding difficulty. Ischaemia of the detrusor can also be the result of unrelieved urine retention.

    Iatrogenic

    It is reported that 80 per cent of patients with voiding disturbance after pelvic procedures will resume usual voiding within six months. Injury to the hypogastric, pelvic and sometimes the pudendal nerve supply results in damage to the sympathetic, parasympathetic and somatic
    nerve fibres. Decreased parasympathetic nerve supply results in decreased bladder contractility and potentially areflexia.

    Ageing

    In addition to metabolic changes, the volume and elasticity of the bladder can change as we get older. The amount of nerves per mm2 of muscle decreases with age and occurs to the same extent in men and women.

    Obstruction

    Prostatic enlargement which causes obstruction is due to hyperplasia or, less frequently, prostate cancer and urethral strictures. Severe vaginal prolapse can lead to obstructed voiding. Faecal impaction is a well recognised cause of obstruction.

    Infection

    Cystitis, urethritis or vulval abscess cause acute retention because of the reduced contractility of the detrusor muscle.

    Medication

    Drugs with antimuscarinic properties block the chemical transmission of acetylcholine so that the muscles relax - examples are tricyclics, antihistamines, ganglion blockers, alphaadrenergic stimulants, phenothiazines and monoamine oxidase inhibitors.

    Spinal cord injury

    The degree of dysfunction is related to the severity and level of impairment. For example, if the injury is above T12, the patient may have a reflex bladder action, which will require minimal intervention. The bladder still has some or all of its reflexes. Patient with injuries at L1 and
    below, for example, in spina bifida, may have a flaccid bladder which does not
    contract. Bladder emptying may need to be assisted.