Evaluation of Female Urinary Incontinence

, , University of Texas Medical School

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Urethral Evaluation

Assessment of urethral mobility. Urethral mobility is classified as type I or II hypermobility, type III nonmobility, or normal according to the degree of change of posterior urethrovesical angle that occurs with straining maneuvers as assessed during fluoroscopy. This classification system was initially described by Green[21] and developed further by McGuire and colleagues.[22] Normal mobility is diagnosed when the increase in posterior urethrovesical angle with straining is less than 110 to 120 degrees. Type I is straightening of the posterior urethrovesical angle to 180 degrees or greater with straining with downward urethral movement of 2 to 3cm. Type II is urethral hypermobility of > 45 degrees to the vertical plane. Type II is associated with downward and backward movement of 3 to 6cm or more. Thus, instead of abdominal pressure being transmitted to the proximal urethra, abdominal pressure results in urethral movement followed by urethral leakage. This classification system further categorizes incontinence on the basis of proximal urethral pressure. In both types of pure urethral hypermobility-related stress incontinence, the proximal urethral pressure is > 20cm H2O when the patient is at rest in the supine position. In contrast, type III incontinence is associated with no urethral mobility during Valsalva maneuvers and a low proximal urethral pressure (< 20 cm H2O). Type III stress incontinence may also be referred to as intrinsic sphincter deficiency.

Intrinsic sphincter deficiency, however, may also occur with urethral hypermobility. (Intrinsic sphincter deficiency and urethral hypermobility are not mutually exclusive conditions.) A different subcategory has evolved, referred to as type II urethral hypermobility with intrinsic sphincter deficiency or type II/III stress incontinence.

Abdominal leak-point pressure. In recent years, a reproducible and simple technique for evaluating intrinsic urethral sphincter function referred to as the abdominal leak-point pressure (ALPP) was established.[23] This technique may be used with or without fluoroscopy to document and quantitate stress incontinence.

After a CMG has been performed, and the detrusor pressure response to filling has been shown to be normal, the urethra may be tested for stress incontinence. Poor compliance may mimic intrinsic sphincter deficiency, hence the importance of making sure that compliance is normal prior to testing for stress incontinence testing.

An ALPP is performed with the patient in the upright position with the bladder filled to half capacity (approximately 200cc). At this volume of bladder filling (with low total bladder pressure) the patient is asked to perform a slow Valsalva maneuver and the total bladder pressure at the point of leakage is identified fluoroscopically. This is the ALPP. However, if a Valsalva maneuver does not generate enough abdominal pressure to cause leakage, the patient performs a series of coughs while the clinician again watches for the total bladder pressure at which leakage occurs in response to that abdominal pressure. Urethral mobility is assessed simultaneously with fluoroscopy to allow classification of urethral sphincter function. A detailed description of the standardized technique is provided by McGuire and colleagues.[23]

Using these techniques, stress incontinence may then be classified as: type I or type II urethral hypermobility, type III, or a combination of type II/III stress incontinence. In types I and II, ALPP are typically > 120cm H2O and 60 to 90cm H2O, respectively. The ALPP in type III stress incontinence (whether or not type II hypermobility is present) is 0 to 60cm H2O.[23] Approximately 24% of patients with type II stress incontinence have a low (0 to 60cm H2O) ALPP. Examples of types of stress incontinence are given in Figures 1, 2, and 3.

Figure 1. Classic type II urethral hypermobility, with abdominal leak point pressure of 106cm H 2O
Figure 2. Woman, 73 years old, with no urethral mobility and abdominal leak point pressure of 29cm H 2O; type III stress incontinence.
Figure 3. Woman, 56 years old, with grade 4 cystocele. Abdominal leak point pressure of 52cm H 2O in addition to urethral hypermobility indicates type II/III stress incontinence.

Therapeutic implications of urethral evaluation. When urethral mobility and the ability to resist leakage driven by abdominal pressure have been assessed, appropriate therapy can be chosen. Type I stress incontinence may be treated with pelvic-floor exercises, imipramine, or a needle suspension. Pure type II stress incontinence can be corrected by a needle suspension or any other type of urethral suspension. Type III stress incontinence may be treated with an injectable agent such as collagen, sling procedure, or an artificial urinary sphincter. For type II/III stress incontinence (hypermobility plus intrinsic sphincter deficiency), a pubovaginal sling is the only treatment that addresses both parts of the problem.

The effect of genital prolapse on urethral evaluation. Any type of genital prolapse may protect a dysfunctional urethra from leakage. Thus in testing for the presence of stress incontinence (which should be suggested by the patient's history), the ALPP may be elevated or indeed there may be no demonstrable leakage. Ghonheim and associates[8] attribute the effects of cystoceles on continence to pressure dissipation (abdominal pressure throughout cystocele), urethral kinking, and urethral compression. To minimize the effect of the genital prolapse on continence, reduce the prolapse and repeat the ALPP measurement. After demonstrating a genital prolapse condition using fluoroscopy and maneuvers that increase abdominal pressure, if the presence or nature of the urethral dysfunction is still unclear, the genital prolapse should be reduced with a vaginal pack, and the testing should be repeated. In this way, the ALPP may be determined even if a large cystocele (or other form of genital prolapse) is present.

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