Terminology and Definitions

Good urogynaecological practice is dependent on the accurate definition of conditions. Any condition can be described in terms of symptoms, signs, and/or urodynamic or non-urodynamic observations. A symptom is the subjective indicator of a disease or change in condition as perceived by the patient and may lead them to seek help. A sign is any abnormality indicative of disease or a health problem, discoverable on examination of the patient; an objective indication of disease or a health problem.

The symptom of incontinence is the complaint of involuntary loss of urine (Abrams et al 2002). However, there are several types of incontinence symptoms. These have been defined by the International Continence Society’s Standardization of Terminology Committee and are shown in Box 52.1. This chapter will focus on ‘stress’ urinary incontinence.

Stress incontinence is a well-recognized and familiar term; however, it can be misinterpreted by patients. Some patients make the assumption that ‘stress’ refers to their psychological state. In an attempt to reduce this confusion, other terms have been suggested such as ‘activity incontinence’ or ‘urethral sphincter incompetence’.

The sign of stress incontinence is the observation of involuntary leakage from the urethra synchronous with effort or physical exertion, or on sneezing or coughing.

However, the urodynamic observation of stress incontinence is defined as the involuntary leakage of urine during filling cystometry, associated with increased intra-abdominal pressure, in the absence of a detrusor contraction.

The variation in prevalence of women in the population with stress incontinence partly depends on whether the presence of a symptom, sign or urodynamic observation is measured. This makes it difficult to be certain of the true prevalence of stress and other types of incontinence.

Epidemiology

The prevalence of incontinence is defined as the probability of being incontinent within the defined population group at a defined time point. The incidence of incontinence is the probability of developing incontinence during a defined period.

Almost all epidemiological studies of incontinence are cross-sectional and assess prevalence. There is a need for longitudinal studies to assess the risk factors, incidence, remission and impact of preventative strategies.

In the epidemiological assessment of the prevalence of incontinence, it is important to define the population because incontinence has been shown to vary with age and race. The prevalence of incontinence in an institutional elderly care setting is much higher than in a community-dwelling young population. Prevalence estimates for the most inclusive definitions of incontinence (e.g. ‘have you ever experienced urinary incontinence’) vary greatly from 5% (van Oyen and van Oyen 2002) to 69% (Swithinbank et al 1999); however, most studies fall within the range of 25–45% (Thomas et al 1980, Yarnell et al 1981, Holst and Wilson 1988, Rekers et al 1992, Lara and Nacey 1994, Hannestad et al 2000).

There is evidence that the prevalence varies depending on the methodology of the questionnaire, such as whether the survey was conducted by telephone or post.

Another factor which greatly impacts on the prevalence of urinary incontinence is bothersomeness. Swithinbank et al (1999) demonstrated that although urinary symptoms are common among the female population, they are not always perceived as a problem. Stress incontinence was experienced, at least occasionally, by 60% of the women, but only half of them felt that it was a problem.

There is less variation when studies asked about daily incontinence. Three studies conducted in women under 60 years of age reported a prevalence of 4–7% (Burgio et al 1991, Miller et al 2000, Samuelson et al 2000), whilst the prevalence in women over 65 years of age was 4–14% (median 9%) (Wetle et al 1995, Nakanishi et al 1997, Brown et al 1999).

Most epidemiological studies assess all types of urinary incontinence, and few have attempted to assess the prevalence of stress incontinence. Overall, approximately half of all incontinent women have stress incontinence. Hannestad et al (2000) demonstrated that there is a regular rise in the proportion of cases of urge incontinence compared with stress incontinence from the age of 40 years. Hunskaar et al (2004), in a large epidemiological study of 29,500 women in four European countries, demonstrated a similar change in the prevalence of different types of incontinence with age. The relative prevalence of mixed urinary incontinence increased with age and that of stress incontinence decreased.

Pathophysiology

Stress incontinence occurs when the intravesical pressure overcomes the closure forces of the urethra. The factors which are necessary for the urethra to remain closed include:

Possible variations in pathophysiology of incontinence can be made considering each of these components of continence (see Chapter 49).

However, in clinical practice, it has not been possible to accurately assess the individual components of the continence mechanism. Instead, a more simplistic approach has been adopted, categorizing stress incontinence into the dichotomous groups: intrinsic sphincter deficiency (ISD) and urethral hypermobility. The pathophysiology of stress incontinence is probably a continuum of the five factors listed above, and until they can be individually quantified, it will remain difficult to predict which specific treatment is most appropriate for an individual patient.

Aetiology

The possible risk factors for stress incontinence are shown in Box 52.2.

Some studies have demonstrated age as a significant risk factor for stress incontinence (Goldberg et al 2003), whilst others have only shown age to be significant in urge incontinence (Nygaard and Lemke 1996, Hannestad et al 2000, Samuelson et al 2000).

There are factors associated with age which may be responsible for incontinence rather than age alone. Resnick (1996) describes these using the mnemonic ‘DIAPERS’: Delerium, Infection, Atrophic changes, Pharmacological, psychological, Excess urine output, Restricted mobility and Stool impaction. Certainly, pharmacological agents such as α-blockers (e.g. doxazosin, an antihypertensive) can cause stress incontinence, and angiotensin-converting enzyme inhibitors can cause chronic cough which may aggravate stress incontinence.

Atrophic changes due to a lack of oestrogen may affect incontinence by decreasing urethral resistance and decreasing α-adrenoreceptor sensitivity in urethral smooth muscle.

There has been controversy about the role of oestrogens in the treatment of stress urinary incontinence, and a meta-analysis concluded that oestrogen did not improve the symptoms of stress incontinence (Ahmed Al-Badr Ross et al 2003).

Pregnancy, regardless of the mode of delivery, is associated with an increase in the prevalence of incontinence, although the majority of cases improve in the puerperium. Burgio et al (2003) found that 60% of women experienced urinary leakage during pregnancy, but this decreased to 11% by 6 weeks post partum. However, women who experience incontinence during pregnancy, even if it resolves in the puerperium, are more likely to experience incontinence in later life than those who have not had incontinence in pregnancy (Viktrup and Lose 2001).

In a large study involving over 15,000 women, Rortveit et al (2003) demonstrated that women who had a vaginal delivery were at greater risk of developing stress incontinence in later life compared with women who delivered by caesarean section (odds ratio 2.4). The evidence regarding the impact of other obstetric factors is less clear; however, there is some evidence that use of forceps increases the risk of urinary incontinence (Farrell et al 2001, Nelson et al 2001).

There is good evidence that obesity has a causal role in the development of stress incontinence. Several studies have demonstrated an association between obesity and stress incontinence (Brown et al 1999, Hannestad et al 2000, Viktrup and Lose 2001, Goldberg et al 2003), which has been confirmed by intervention studies of bariatric surgery (Deitel et al 1988, Bump et al 1992) and weight loss programmes (Auwad et al 2008). In the treatment group, there was a reduction of stress incontinence from 61% to 12% (Deitel et al 1988).

Epidemiological studies have demonstrated that the prevalence of stress incontinence is lower in Black African women (27%) compared with White women (61%) (Bump 1993). Thom et al (2006) found similar differences when comparing Black American women with White American women, and they adjusted for age, parity, hysterectomy, oestrogen use, body mass, menopausal status and diabetes. They suggested the presence of a protective factor in Black women.

Inherent differences in connective tissue may predispose to stress incontinence. Young nulliparous premenopausal women with stress incontinence had a decreased collagen I : III ratio compared with controls (Keane et al 1997).

Assessment

The assessment involves history, examination and investigations.

A detailed history is required using language that the patient understands. The International Continence Society has produced a document which standardizes the terminology of lower urinary tract symptoms (Abrams et al 2002), although these are not terms which patients will necessarily understand. The confusion caused by the term ‘stress incontinence’ has been highlighted. It is preferable to use a standardized validated symptom questionnaire to elicit the patient’s symptoms. Terms which are not well understood are usually removed in the validation process. Such tools can be completed by the physician or the patient. They ensure that symptoms are not missed and may help patients to describe symptoms which they find embarrassing.

It is important to ask about the impact of stress incontinence on sexual function. In one study, 68% of women stated that their sex life was affected by their urinary symptoms (Ward and Hilton 2002).

Several validated symptom questionnaires exist, and the main differences are content. Some only address symptoms of stress incontinence; for example, the Severity of Symptoms Index developed by Black et al (1996). Others, such as the Kings Health Questionnaire (Kelleher et al 1997) and the Bristol Female Lower Urinary Tract Symptom (BFLUTS) Questionnaire (Jackson et al 1996), assess all lower urinary tract symptoms, and some assess all pelvic floor symptoms (Barber et al 2001, Radley et al 2006).

Recently published national guidelines in the UK (National Institute for Health and Clinical Excellence 2006) and the USA (Agency for Health Care Policy and Research 1992, 1996) even suggested that patients who only had the symptoms of pure stress incontinence could be treated surgically without the need for twin channel cystometry.

Harvey and Versi (2001) evaluated the symptoms and signs of stress incontinence in predicting the presence of urodynamic stress incontinence, and found that the isolated symptom of stress incontinence had a positive predictive value of only 56% for the diagnosis of pure urodynamic stress incontinence. This implies that history alone is not reliable in establishing a diagnosis. In practice, most urogynaecologists and urologists still perform urodynamics prior to surgery. If a detailed symptom questionnaire is used to elicit the history, few patients have ‘pure’ stress incontinence alone.

Some symptom questionnaires, such as BLFUTS and ePAQ (Electronic Personal Assessment Questionnaire), separately assess the degree of bother that each symptom causes and the severity of the symptom (Jackson et al 1996, Radley et al 2006). Epidemiological studies have shown that although symptoms of leakage are very common, occurring in up to 60% of the population, less than half of women are bothered by them (Swithinbank et al 1999). Hence, an assessment of bother is important. The degree to which a symptom causes bother may be specific to the patient’s lifestyle and personality. Each individual patient will have their own expectations about treatment and goals which they hope to achieve. In clinical practice, it is important to establish whether or not the patient’s goals are attainable.

In research or audit, a formal assessment of the impact of incontinence on a patient’s quality of life can be made using a quality-of-life questionnaire. There are a large number of validated quality instruments available. The International Consultation on Incontinence (ICI) has appraised and rated the existing instruments (Donovan and Bosch 2005).

When taking a history of urinary symptoms, it is also important to consider past medical and surgical history which impacts on the diagnosis. Vesicovaginal fistulae following hysterectomy are uncommon but may be missed and diagnosed as stress incontinence.

Previous continence surgery may produce new urinary symptoms including voiding dysfunction, and may decrease the success rates of future surgery.

Examination

Physical examination of all patients with stress incontinence is important. Body mass index (BMI; kg/m²) should be recorded because there is good evidence that links incontinence with high BMI (Hannestad et al 2000). General abdominal examination may reveal striae suggestive of underlying collagen disorders. There may also be evidence of benign joint hypermobility with hyperextension of joints. A general assessment of the patient’s mobility and dexterity should be made with a view to considering if they would be capable of performing self-catheterization post operatively if necessary. A general neurological assessment should be performed because the presence of neurological disease may indicate an early need for urodynamics instead of conservative treatment.

Pelvic examination is performed to assess:

Urinary leakage can be observed during a cough test which is normally performed in dorsal lithotomy with a comfortably full bladder. Stress incontinence is the observation of involuntary leakage from the urethra, synchronous with coughing or straining. A cough may induce a detrusor contraction which then causes leakage, but this can only be distinguished during cystometry. It is important to establish that leakage is not extraurethral from a urinary fistula or ectopic ureter.

Urethral mobility can be assessed visually. The patient is asked to cough or perform a Valsalva manoeuvre; if hypermobility is present, the anterior vaginal wall will rotate outwards and the urethral meatus towards the ceiling. Many clinicians will select the type of surgical intervention depending on the presence or absence of urethral mobility.

The levator ani can be assessed digitally just inside the posterior forchette on the left and right of the midline. The Modified Oxford Scale (Laycock and Jerwood 2001) (Table 52.1) provides a useful grading scale of the muscle, and has been shown to correlate well with surface electromyography and manometry (Haslam 1999).

Table 52.1 The Modified Oxford Scale for pelvic floor muscles (PFM)

It is always important to perform a visual inspection of the cervix because, occasionally, the leakage is due to copious vaginal discharge not urine. If there is doubt, an agent such as Pyridium can be used to stain urine.

The perineal skin should be assessed since it may be excoriated from inappropriate pad use, atrophy and ammoniacal dermatitis.

The presence of prolapse should be documented using a standardized assessment such as the pelvic organ quantification system (POP-Q) (Bump et al 1996). The advantage of POP-Q is that it has been shown to be reproducible.

Investigations

Treatment