Urinary incontinence is the involuntary loss of urine that is so severe as to have social or hygienic consequences. It is very common, with a prevalence in community-dwelling elderly persons as high as 35%, and significantly higher rates among institutionalized patients. Despite this high prevalence, studies have shown that about half of all incontinent persons have never discussed the problem with a physician. This is likely because of embarrassment, a belief that incontinence is normal with aging, or an assumption that nothing can be done to help. Incontinence is associated with significant medical morbidity, including infection, sepsis, pressure ulcers, and falls. It is also associated with significant psychological stress and social isolation. Incontinence causes significant caregiver burden, and is frequently cited as a reason for deciding to abandon home care efforts in favor of nursing home placement. The economic burden of incontinence is also substantial, with an estimated direct cost in the United States of $16.3 billion per year.

Because of its high prevalence, significant morbidity, and high psychosocial impact, it is important for family physicians to accurately identify, assess, and treat incontinent patients. The large majority of patients with incontinence can be diagnosed and managed effectively by family physicians in the primary care setting.

Physiology of Normal Urination

A basic understanding of the normal physiology of urination is important to understand the potential causes of incontinence, and the various strategies for effective treatment.

The lower urinary tract consists primarily of the bladder (detrusor muscle) and the urethra. The urethra contains two sphincters, the internal urethral sphincter (IUS), composed predominantly of smooth muscle, and the external urethral sphincter (EUS), which is primarily voluntary muscle. The detrusor muscle of the bladder is innervated predominantly by cholinergic (muscarinic) neurons from the parasympathetic nervous system, the stimulation of which leads to bladder contraction. The sympathetic nervous system innervates both the bladder and the IUS. Sympathetic innervation in the bladder is primarily β-adrenergic and leads to bladder relaxation, whereas α-adrenergic receptors predominate in the IUS, leading to sphincter contraction. Thus, in general, sympathetic stimulation of the urinary tract promotes bladder filling (relaxation of the detrusor with contraction of the sphincter), whereas parasympathetic stimulation leads to bladder emptying (detrusor contraction and sphincter relaxation).

The EUS, on the other hand, is striated muscle and primarily under voluntary (somatic) control. This allows for some ability to voluntarily postpone urination by tightening the sphincter and inhibiting the flow of urine. Additional voluntary control is provided by the central nervous system through the pontine micturition center. This allows for central inhibition of the autonomic processes previously described, and for further voluntary postponement of the need to urinate until the circumstances are more socially appropriate or until necessary facilities are available.

The physiologic factors influencing normal urination are summarized in Table 41-1 and are important considerations when discussing urinary disorders and treatment.

Age-Related Changes

Contrary to common perception, urinary incontinence is not inevitable with aging. Most elderly patients remain continent throughout their lifetimes, and a complaint of incontinence at any age should receive a thorough evaluation and not be dismissed as “normal for age.” Nonetheless, many common age-related changes predispose elderly patients to incontinence and increase the likelihood of its development with advancing age.

The frequency of involuntary bladder contractions (detrusor hyperactivity) increases in both men and women with aging. In addition, total bladder capacity decreases, causing the voiding urge to occur at lower volumes. Bladder contractility decreases, leading to increased postvoid residuals and increased sensation of urgency or fullness. Elderly patients excrete a larger percentage of their fluid volume later in the day than younger persons. This, in addition to the other changes listed, often leads to an increase in the incidence of nocturia with aging, and more frequent nighttime awakenings.

In women, menopausal estrogen decline leads to urogenital atrophy and a decrease in the sensitivity of α-receptors in the IUS. In men, prostatic hypertrophy can lead to increased urethral resistance, and varying degrees of urethral obstruction.

It is important to remember that these age-related changes are found in many healthy, continent persons as well as those who develop incontinence. It is not completely understood why the predisposition to urinary problems is stronger in some patients than in others, which emphasizes the multifactorial basis of incontinence.

Symptoms and Signs

Incontinence Outside the Urinary Tract

Incontinence is often classified based on whether it is related to specific urogenital pathology or to factors outside the urinary tract. Terms such as transient versus established, acute versus persistent, and primary versus secondary have been used to highlight this distinction. The mnemonic DIAPPERS is helpful in remembering the many causes of incontinence that occur outside the urinary tract (Table 41-2). These “extraurinary” causes are very common in the elderly, and it is important to identify or rule them out before proceeding to a more invasive search for primary urogenital etiologies.

Delirium, depression, and disorders of excessive urinary output generally require medical or behavioral management of the primary cause rather than strategies relating to the bladder. Once the primary causes are corrected, the incontinence often resolves. Urinary tract infections, although easily treated if discovered, are a relatively infrequent cause of urinary incontinence in the absence of other classic symptoms (dysuria, urgency, frequency, etc). Asymptomatic bacteriuria, which is common even in well elderly, does not cause incontinence.

Pharmaceuticals are a particularly important and very common cause of incontinence. Because of the many neural receptors involved in urination (see Table 41-1), it is easy to understand why so many medications used to treat other common problems can readily affect continence. Medications frequently associated with incontinence are listed in Table 41-3. Many of these medications are available over the counter and in combination (Table 41-4). In addition, commonly used substances such as caffeine and alcohol can contribute to incontinence by virtue of their diuretic effects or the effects they have on mental status. Because of this, some medications and substances associated with a patient’s incontinence may not be considered important or readily volunteered during a medication history unless the physician specifically asks about them.

Restricted mobility or the inability to physically get to the bathroom in time to avoid incontinence is also referred to as “functional” incontinence. The incontinence may be temporary or chronic, depending on the nature of the physical or cognitive disability involved. Physical therapy or strength and flexibility training may be helpful, as well as simple measures such as a bedside commode or urinal.

Stool impaction is very common in the elderly and may cause incontinence both through its local mass effect and by stimulation of opioid receptors in the bowel. It has been reported to be a causative factor in up to 10% of patients referred to incontinence clinics for evaluation. Continence can often be restored by a simple disimpaction.

Urologic Causes of Incontinence

Once secondary or transient causes have been investigated and ruled out, further evaluation should focus on specific urologic pathology that may be causing incontinence.

The urinary tract has two basic functions: the emptying of urine during voiding and the storage of urine between voiding. A defect in either of these basic functions can cause incontinence, and it is useful to initially classify incontinence by whether it is primarily a defect of storage or of emptying. An inability to store urine occurs when the bladder contracts too often (or at inappropriate times), or when the sphincter(s) cannot contract sufficiently to allow the bladder to store urine and keep it from leaking. Thus the bladder rarely, if ever, fills to capacity and the patient’s symptoms are generally characterized by frequent incontinent episodes of relatively small volume. An inability to empty urine occurs when the bladder is unable to contract appropriately, or when the outlet or sphincter(s) is partially obstructed (either physically or physiologically). Thus, the bladder continues to fill beyond its normal capacity and eventually overflows, causing the patient to experience abdominal distention and continual or frequent leakage.

Determining whether the primary problem is the inability to store or the inability to empty can often be done easily during the history and physical examination based on the patient’s pattern of incontinence (intermittent or continuous) and whether abdominal (bladder) distention is present. Determination of postvoid residual is also helpful in making this distinction (see section History and Physical Findings, later). This initial classification is important in narrowing down the specific etiology of the incontinence, and in ultimately deciding on the appropriate management strategy.

Symptomatic Classification

Once it is determined whether the primary problem is with storage or with emptying, incontinence can be further classified according to the type of symptoms that it causes in the patient. The most common categories are discussed below. The first two types, urge incontinence and stress incontinence, result from an inability to store urine. The third type, overflow incontinence, results from an inability to empty urine. Because the term “overflow” has been felt by many to be confusing and imprecise, the term “incomplete bladder emptying” is now often used instead. A patient may have a single type of incontinence or a combination of more than one type (mixed incontinence). Table 41-5 summarizes the major categories of incontinence, the underlying urodynamic findings, and the most common etiologies for each.

Urge Incontinence

Urge incontinence is the most common type of incontinence in the elderly. Patients complain of a strong, and often immediate, urge to void followed by an involuntary loss of urine. It is often not possible to reach the bathroom in time to avoid incontinence once the urge occurs, and patients often lose urine while rushing toward a bathroom or trying to locate one. Urge incontinence is most frequently caused by involuntary contractions of the bladder, often referred to as detrusor instability. These involuntary contractions increase in frequency with age, as does the ability to voluntarily inhibit them. Although the symptoms of urgency are a hallmark feature of this type of incontinence, detrusor instability can sometimes result in incontinence without these symptoms. Although most patients with detrusor instability are neurologically normal, uninhibited contractions can also occur as the result of neurologic disorders such as stroke, dementia, or spinal cord injury. In these cases it is often referred to as detrusor hyperreflexia. Detrusor instability and urgency can also be caused by local irritation of the bladder as with infection, bladder stones, or tumors. The term overactive bladder syndrome (OABS) is now commonly used to describe the symptoms of urgency caused by detrusor instability and to emphasize that they can occur either with or without incontinence. OABS is described by the International Continence Society as voiding eight or more times during a 24-hour period, and awakening two or more times during the night. Treatment of OABS is similar whether or not incontinence is present.

Stress Incontinence

Stress incontinence is much more common among women than men and is defined as a loss of urine associated with increases in intra-abdominal pressure (Valsalva maneuver). Patients complain of leakage of urine (usually small amounts) during coughing, laughing, sneezing, or exercising. In women, stress incontinence is most often caused by urethral hypermobility resulting from weakness of the pelvic floor musculature, but it can also be caused by intrinsic weakness of the urethral sphincter(s), most commonly following trauma, radiation, or surgery. Stress incontinence is rare in men, unless they have suffered damage to the sphincter through surgery or trauma. In making the diagnosis of stress incontinence, it is important to ascertain that the leakage occurs exactly coincident with the stress maneuver. If the leakage occurs several seconds after the maneuver, it is more likely caused by an uninhibited bladder contraction that has been triggered by the stress maneuver, and is urodynamically more similar to urge incontinence. This is sometimes known as stress-induced detrusor instability.