Filling and storage phase.

The ICS classification of abnormalities of the storage and voiding phases is outlined in Box 8.1 and diagrammed in Fig. 8.1 . Cystometry measures the pressure/volume relationship of the bladder during filling and storage and assesses bladder function in terms of bladder sensation, detrusor activity, bladder capacity, and bladder compliance.

Abnormalities of storage and voiding phases. SUI, Stress urinary incontinence; ISD , intrinsic sphincter deficiency.

Detrusor activity may be normal or overactive. Overactive detrusor function is characterized by involuntary detrusor contractions during filling. These contractions may be spontaneous or provoked and cannot be suppressed completely. Overactive detrusor function in the absence of a known neurologic abnormality is called idiopathic detrusor overactivity, and overactivity caused by disturbance of the nervous control mechanisms is called neurogenic detrusor overactivity. These conditions are often associated with the symptom of urinary urgency. Urgency, with or without urgency incontinence, usually with frequency and nocturia in the absence of urinary tract infection or obvious pathology, is described as overactive bladder (urgency) syndrome. Terminology used to describe overactive bladder is provided in Box 8.2 .

Urethral function during storage can be assessed clinically (direct observation of urine loss with cough or Valsalva maneuver), urodynamically (urethral closure pressure profilometry and leak point pressure measurements), or radiographically (cystourethrography with or without video). The urethral closure mechanism may be competent or incompetent. An incompetent urethral closure mechanism is one that allows leakage of urine during activities, which may raise intraabdominal pressures in the absence of a detrusor contraction. Involuntary leakage during filling cystometry may occur during increased abdominal pressure, in the absence of a detrusor contraction (urodynamic stress incontinence), or because of urethral relaxation in the absence of raised abdominal pressure or detrusor overactivity (urethral relaxation incompetence). The definition and significance of the latter condition await additional data.

Urinary incontinence is the complaint of any involuntary (urethral or extraurethral) leakage of urine. Urinary incontinence is a symptom, a sign, and a condition. Urinary incontinence as a symptom means that the patient states that she has involuntary urine loss. Types of incontinence symptoms include stress incontinence, urgency incontinence, mixed incontinence, nocturnal enuresis, situational incontinence, and continuous incontinence. In each specific circumstance, urinary incontinence should be further described by specifying relevant factors such as type, frequency, severity, precipitating factors, social impact, effect on hygiene and quality of life, the measures used to contain leakage, and whether or not the individual seeks or desires help because of urinary incontinence. The sign of stress incontinence denotes the observation of urine loss from the external urethral meatus synchronously with physical exertion such as a cough or Valsalva maneuver. Because symptoms and signs of urinary incontinence are sometimes misleading, accurate diagnosis often requires urodynamic investigation in addition to careful history and physical examination.

Voiding phase.

During the voiding phase, the detrusor muscle may be normal, underactive, or acontractile. Normal voiding usually is achieved by an initial voluntary reduction in intraurethral pressure (urethral relaxation) followed by a continuous detrusor contraction that leads to complete bladder emptying within a normal time span, and in the absence of obstruction. Detrusor underactivity during micturition is defined as a contraction of reduced strength and/or duration, resulting in prolonged bladder emptying and/or a failure to achieve complete bladder emptying within a normal time span. An acontractile detrusor is one that cannot be demonstrated to contract during urodynamic studies, resulting in incomplete bladder emptying.

During voiding, urethral function may be normal or abnormal. Abnormal urethral function may be caused by uncoordinated or involuntary urethral contractions, urethral stricture, or obstruction from an anatomic abnormality such as severe pelvic organ prolapse or changes after a stress incontinence procedure.

Simultaneous measurement of intravesical or detrusor pressure and urine flow is necessary to determine whether the patient’s voiding is obstructive. In general, high detrusor pressures with low flow rates suggest an obstructive problem, whereas low detrusor pressures with low flow rates imply that the problem is one of detrusor underactivity or acontractility. Simultaneous external urethral sphincter electromyography is necessary to determine whether an obstructive voiding pattern is secondary to urethral overactivity or mechanical obstruction.