5 Description and Classification of Lower Urinary Tract Dysfunction and Pelvic Organ Prolapse

CLASSIFICATION SYSTEMS OF LOWER URINARY TRACT DYSFUNCTION 55

International Continence Society Classification 55

DIFFERENTIAL DIAGNOSIS OF URINARY INCONTINENCE 56

DESCRIPTION AND STAGING OF PELVIC ORGAN PROLAPSE 58

CLASSIFICATION SYSTEMS OF LOWER URINARY TRACT DYSFUNCTION

The purpose of any classification system is to facilitate understanding of the etiology and pathophysiology of disease, to help establish and standardize treatment and research guidelines, and to avoid confusion among those who are concerned with the problem. Several classification systems for voiding disorders and urinary incontinence have been developed. These classifications have been based on various anatomic, radiographic, and urodynamic findings. The advantages, disadvantages, and applicability of the various classification systems of voiding dysfunction were described by Wein and Barrett (1988). This chapter reviews two practical systems for the classification of voiding dysfunction in women. Also, the differential diagnosis of urinary incontinence in women is discussed using updated terminology from the International Continence Society (ICS). Hopefully, the nomenclature used in these classification systems will become more widely understood and used and further research will be aimed at defining their clinical applicability.

International Continence Society Classification

In 1973 the ICS established a committee for the standardization of terminology of lower urinary tract function. Five of the first six reports from this committee were published. These reports were revised, extended, and collated in a monograph published in 1990 (see Appendix A). The definitions were updated and revised by the Standardization Subcommittee of the ICS in 2002 (see Appendix B). The following is a summary of its findings.

The lower urinary tract is composed of the bladder and urethra, which work together as a functional unit to promote storage and emptying of urine. Symptoms, signs, urodynamic observations, and conditions are separate categories with unique but overlapping terminologies. Although a complete urodynamic investigation is not necessary for all symptomatic patients, some clinical or urodynamic assessment of the filling and voiding phases is essential for each patient. Examining bladder and urethral activity separately is useful in each phase. If urodynamic studies are performed, results should clearly reflect the patient’s symptoms and signs.

FILLING AND STORAGE PHASE

The ICS classification of abnormalities of the storage and voiding phases is outlined in Box 5-1. Cystometry is used to examine the bladder during filling and storage. Function should be described in terms of bladder sensation, detrusor activity, bladder capacity, and bladder compliance.

Detrusor activity may be normal or overactive. Overactive detrusor function is characterized by involuntary detrusor contractions during filling. They 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; 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 urge incontinence, usually with frequency and nocturia, is described as the overactive bladder syndrome, urge syndrome, or urgency-frequency syndrome.

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 in the absence of a detrusor contraction. Leakage may occur during increased abdominal pressure, in the absence of a detrusor contraction (urodynamic stress incontinence) or due to urethral relaxation in the presence of raised abdominal pressure or detrusor overactivity (urethral relaxation incontinence). 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, urge 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 is usually achieved by a voluntarily initiated continuous detrusor contraction that leads to complete bladder emptying within a normal time span and in the absence of obstruction. An underactive detrusor during micturition implies that the detrusor contraction is of inadequate magnitude or duration to effect bladder emptying within a normal time span. Acontractile detrusor is one that cannot be demonstrated to contract during urodynamic studies.

During voiding, urethral function may be normal or abnormal. Abnormal urethral function may be due to either obstruction or urethral overactivity, or to a urethra that cannot open due to anatomic abnormality, such as severe pelvic organ prolapse or urethral stricture.

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 a result of urethral overactivity or mechanical obstruction.

Functional Classification

Wein (1981) classified voiding dysfunction on a functional basis, describing the dysfunction simply in terms of whether the deficit is primarily one of the filling/storage phase or the voiding phase. Each section is subcategorized into whether the deficit is one of the bladder or the outlet. The expanded functional classification, with relevant conditions as suggested by Wein (1998), is shown in Box 5-2.

BOX 5-2 EXPANDED FUNCTIONAL CLASSIFICATION