During the filling cycle, stretch receptors within the bladder detrusor muscle signal low intensity afferent impulses to the spinal cord via the pelvic nerves (S2–S4) and then via the spinal cord (lateral spinothalamic tracts) to the pontine micturition centre and the frontal cortex. This results in three processes:

These spinal reflexes are collectively known as the “guarding reflex” allowing one to remain continent. Furthermore, several studies have suggested that a region within the lateral pons of the brain known as the “pontine storage area” may contribute to this process by stimulating striated urethral sphincter activity [28–30].

The bladder is usually able to hold approximately 500 ml of urine before needing to empty. At a critical level of bladder distention, the afferent impulses in the pelvic nerves intensify to the spinal cord, switching the spinobulbospinal pathway to maximal activity [28]. These signals are relayed from the spinal cord to the pontine micturition centre of the brain via the periaqueductal grey. Activation of the pontine micturition centre results in the following:

Voluntary voiding is under strict control from higher brain centres, which have been identified using functional magnetic resonance imaging. These include the prefrontal cortex—in particular the right inferior prefrontal gyrus—the anterior cingulate cortex, the thalamus, the caudal hypothalamus, and the insula [28, 30]. The periaqueductal grey plays a pivotal role in relaying signals to and from these higher brain centres to control primary input into the pontine micturition centre. This process ensures that voiding only takes place when it is considered to be socially desirable to do so and effectively suppressed at all other times [28–31].

This is the most frequently reported cause of post-stroke urinary incontinence [15, 32, 33]. The stroke lesion itself may directly disrupt the neuromicturition pathways within the brain, resulting in uninhibited detrusor contractions. The consequence of detrusor overactivity is often a sudden urge to void that is difficult to postpone, and subsequently may result in the involuntary leakage of urine. The strength of the contractions will determine the degree of urinary leakage, with stronger ones resulting in complete bladder emptying. Conversely, weaker contractions lead to frequent small-volume leakages and ineffective bladder emptying, which results in large residual volumes of urine [>100 ml]. Thus, patients with urge incontinence also complain of symptoms of urinary frequency and nocturia [33]. Detrusor overactivity is also referred to as detrusor hyper-reflexia and can be demonstrated using urodynamic studies; however, this investigation is not routinely required. Studies using urodynamic evaluation of stroke patients have reported a wide variation in prevalence rates of this condition, ranging from 37 to 90 % [15, 34, 35]. There is inconclusive data associating the site of the stroke lesion and the development of urge incontinence; however, lesions in the frontal lobe have been suggested [34, 36].

This type of post-stroke incontinence has been reported in various studies, with prevalence rates ranging from 21 % to 35 % [15, 17, 32, 37]. It has been postulated that detrusor hyporeflexia may occur after an acute stroke because of an initial loss of bladder tone. However, in most of these studies, non-stroke factors were also present such as use of anticholinergic medications or diabetic polyneuropathy, which can affect bladder tone and result in overflow incontinence [15]. Detrusor hyporeflexia results in the incomplete bladder emptying, resulting in large post-void residual urine volumes (>100 ml) and subsequent symptoms of dribbling and/or continuous leakage of urine. The resultant urinary retention may occur acutely, and is usually very painful, or it may be chronic, developing over a longer period of time, in which case it is usually painless. In all cases of urinary retention, constipation must be excluded as a causative factor.

A few prospective hospital-based trials have explored the concept of impaired awareness of urinary incontinence in acute stroke patients [36, 38, 39]. This type of incontinence has been defined as “Urinary incontinence with reduced ability to be aware of bladder signals before leakage, to take notice of eventual leakage, or both” [39]. In a cohort of 65 patients, more than half were found to have impaired awareness of their symptoms, ranging from slight unawareness to anosognosia. The authors reported that this type of incontinence appeared to be an independent risk factor for poor outcome both at 3 months and 1 year following stroke [38, 39]. When compared to patients with urge incontinence, it was found that those with impaired awareness had a greater frequency of parietal stroke lesions and, less frequently, frontal lesions. This finding was consistent with the known role of the parietal and temporal lobes in correctly identifying and validating signals in a given social circumstance, compared to the volitional role of the frontal lobe structures in the conscious recognition of afferent bladder signals.

Stroke-related factors, such as cognitive, communicative, or mobility difficulties, may impact indirectly on the patient’s ability to maintain effective toileting skills despite normal bladder function [5, 7, 15]. The resulting “functional” incontinence has been significantly associated with aphasia and/or cognitive impairment [15]. In another study, the following stroke-related factors were reported on multivariate analysis to be significantly associated with initial urinary incontinence: visual field defects, dysphagia, motor weakness, and age over 75 years.

This type of incontinence does not occur as a direct consequence of stroke; however, stroke-related factors might aggravate a pre-existing condition. Stress incontinence occurs upon exertion (standing, coughing, and sneezing) and it is primarily the consequence of weakness of the pelvic floor muscles [4]. Reduced pelvic muscle tone and motor weakness resulting from an acute stroke can lead to greater exertional efforts in toileting, exacerbating pre-existing stress incontinence. Acute stroke can also be complicated by aspiration pneumonia, and the resulting cough may also aggravate this type of incontinence [40].

These transient causes are potentially reversible and, if present, it is imperative that they are adequately addressed. The pneumonic “DIAPPERS” illustrates these causes [41]:

All stroke units should have an agreed protocol for the assessment of urinary incontinence. Firstly, all patients admitted to hospital following an acute stroke should undergo a basic assessment of their bladder function to identify any problems. This initial assessment can be carried out by nursing staff and should include a urine dipstick to identify the presence of a urinary tract infection. If bladder problems are identified, then a full continence assessment should be undertaken to identify the type of urinary incontinence and any contributing factors.

This should be undertaken as soon a bladder problem such as urinary incontinence is identified. It is important to appreciate that this is a personal assessment regarding a potentially sensitive topic, which requires both time and privacy. Although there are very few studies evaluating the different assessment processes used, Table 8.2 outlines a framework for the assessment of urinary incontinence. This assessment should guide the development of a suitable treatment strategy tailored to the individual patient’s needs.

Table 8.2 illustrates the key components of the clinical history, which must be ascertained in all patients with urinary incontinence. It is essential to establish whether there were any pre-existing bladder problems prior to the stroke. Any previous gynaecological or urological procedures undertaken must also be noted, as they may impact on the current bladder complaints. Co-existing conditions such as diabetes, multiple sclerosis, spinal injuries, and dementia may also contribute to urinary incontinence. A full medication history must also be sought, as several drugs have been associated with bladder problems, including the following: antimuscarinic agents (urinary retention and constipation), diuretics (polyuria), sedatives (mobility problems and confusion), calcium channel antagonists (urinary retention and constipation), opiates (urinary retention, constipation, confusion, and reduced mobility), and cholinesterase inhibitors (increase bladder contractility). In addition to the questions outlined in Table 8.2, specific bladder-related questions should be included in the history to identify the presence of the following symptoms:

These questions will help to determine the type of urinary incontinence, the severity, and pattern of the symptoms and will enable the healthcare professional to plan an appropriate treatment strategy.

Finally, social and environmental factors must also be assessed, although this could be done in the latter stages of the patient’s admission, closer to the time of discharge. These factors include the impact of incontinence on the patient’s social activities, work life, and sexual relationships.

Clinical assessment of a patient with urinary incontinence should include the following:

A patient’s ability to actually use a toilet may be affected by stroke, and therefore an evaluation of this is imperative as part of the continence assessment. Both physical and cognitive difficulties may contribute, and these should be formally assessed using validated standardised tests such as the Mini Mental State Examination [42]. Key components of this assessment should include the following information:

This assessment method is very important for all patients suffering from urinary incontinence. It involves recording the frequency and volume of all fluid intake and of all urine output over a minimum of 3 days. The optimum duration that a bladder diary should be kept is unclear from clinical studies; however, this assessment method is useful in determining the best schedule for bladder training strategies [4]. The chart should inform the healthcare professional regarding the following: