and anal sphincter relaxation during strain provide a measure of proper of the appropriateness of pelvic floor function. Failure of relaxation or very high anal sphincter resting pressure suggests dyssynergic defecation. The presence of weak anal sphincter pressures may place the patient at risk for incontinence during treatment of the constipation.
Rectal prolapse can be associated with difficult evacuation due to blockage of the anal canal with the rectum. These patients usually also described episodes of bowel incontinence. A more severe rectal prolapse can be identified during strain in the left lateral decubitus position. A better way to assess for rectal prolapse is to have the patient strain over a commode. The examiner places a gloved hand below the anus and can feel the rectal prolapse descend and touch the glove. The degree of rectal prolapse can be assessed by visual inspection. The physical examination, including rectal examination, is a necessary part of the evaluation of any constipated patient.
Diagnostic tests
Laboratory tests often recommended in evaluating constipation include a complete blood count; a metabolic panel that includes electrolytes, creatinine, magnesium, and calcium; and thyroid function tests. If malignancy is suspected, the stool should be assessed for the presence of occult blood. The need for a colonic structural examination is dictated by the need for routine colorectal screening and the presence of red‐flag signs such as rectal bleeding, anaemia, unintentional weight loss, or a recent change in bowel habit. Colonoscopy in patients over the age of 80 carries a greater risk of complications, adverse events, and higher morbidity than in younger patients. It is also associated with a higher chance of poor bowel preparation resulting in inadequate imaging and lower completion rates.34 Therefore, colonoscopy should be performed after careful consideration for the risks and benefits to the individual patient.
Many patients with long‐standing constipation and no red‐flag symptoms can undergo a therapeutic trial with fibre or an osmotic laxative, preserving further evaluation for those who fail to respond to simple interventions. Patients with more severe or medication‐unresponsive constipation may benefit from further evaluation, including physiological testing. It is difficult to predict the underlying pathophysiology of chronic constipation by symptoms alone.35 The presence of slow‐transit constipation or dyssynergic defecation may be suspected by a poor response to a trial of supplemental fibre.36
Currently, additional tests include colon transit measurement, colonic manometry, anorectal manometry, balloon expulsion testing, and defecography. Colonic transit measurements may be performed scintigraphically or using radiopaque markers and plain abdominal radiographs. In practice, few centres have scintigraphy readily available. A variety of techniques have been described for measuring colonic transit using radiopaque markers, some providing data on regional colon transit. Since treatments have not yet been identified for treating regional colonic abnormalities, total colon transit measurements suffice. New imaging techniques to measure gastrointestinal transit are emerging, including tracking magnetic capsules or wireless devices and MRI‐based methods offering cross‐sectional imaging and assessing transit.37 A widely used method to measure colon transit time is the five‐day colon transit measurement using radiopaque markers; it is simple to perform and cost‐effective, but the technique does involve radiation exposure. 24 radiopaque markers (Sitzmark) are ingested, and a plain abdominal radiograph is performed 5 days later.38 Transit is considered prolonged when >20% of the markers (five or more) remain (Figure 20.2). Although markers remaining predominantly in the rectum suggest dyssynergic defecation or outlet dysfunction, the distribution pattern of the markers throughout the colon does not reliably differentiate between primary slow‐transit versus colon transit delayed as a result of outlet dysfunction (i.e. dyssynergic defecation). Normal subjects pass more than 80% of markers within 120 hours.38
Figure 20.2 An abdominal radiograph obtained 5 days after ingestion of a capsule containing 24 radiopaque markers (small circles). The presence of >5 markers on day 5 indicates the presence of slow colonic transit. The majority of the markers reside in the rectum, with a few markers scattered in the sigmoid and descending colon.
Dyssynergic defecation is common and refers to physiological difficulty with the rectal evacuation process due to an inability to coordinate the abdominal and pelvic floor muscles. Synonyms include pelvic outlet dysfunction, pelvic floor dysfunction, anismus, and paradoxical puborectalis contraction. Uncommonly, difficult rectal evacuation may be due to an anal stricture, obstructing rectocele or internal intussusception. The last two findings are most often the result of abnormal straining rather than a primary problem themselves. The presence of dyssynergic defecation can be evaluated by anorectal manometry, electromyography of the anal sphincter, balloon defecation, and defecography. Anorectal manometry involves measuring the pressures of the anal sphincter with a manometric probe in response to different manoeuvres, including straining. During strain, a rise in intra‐rectal pressure should occur, and the external anal sphincter should relax. The presence of a paradoxical increase in sphincter pressure suggests the possibility of dyssynergic defecation. False positives occur at least 10% of the time with all tests of pelvic floor function. Therefore, two tests that independently confirm the same findings are required to make a secure diagnosis of dyssynergic defecation.39
Balloon expulsion testing is performed by placing a small balloon in the rectum and filling the balloon with 50–60 ml of warm water. The patient is asked to sit on a commode and expel the balloon. Normal expulsion occurs in one minute or less. A prolonged time or failure to expel the balloon suggests dyssynergic defecation.39 Anorectal manometry and balloon expulsion testing are the most commonly performed tests to identify dyssynergic defecation. Electromyography also assesses for proper anal sphincter muscle relaxation and contraction. The need to place needles in the anal sphincter makes this technique less attractive for most patients.
Defecography is a dynamic fluoroscopy study that involves placing a barium paste in the rectum and then obtaining radiographs during defecation in a sitting position.39 Defecography assesses the opening of the anorectal angle and provides an assessment of sphincter opening, perineal descent, and rectal emptying. Defecography typically is reserved for cases where an underlying structural abnormality is suspected or when other tests for dyssynergic defecation are equivocal. It provides useful information for the diagnosis of rectoceles, intussusception, and rectal prolapse.39
Additional physiological tests of colon transit and pelvic floor function are required in only the subset of patients who are refractory to medical management. Magnetic resonance defecography or dynamic pelvic MRI is a newer technique that can be used to assess pelvic floor anatomy and defecation, although due to its high cost and lack of availability, its use is currently limited.40,41 Patients with refractory symptoms and normal physiological studies are defined as having normal transit constipation. Many of these patients meet the criteria for irritable bowel syndrome, particularly if their symptoms have been long‐standing.
Treatment
The management of chronic constipation in the elderly aims to relieve symptoms related to constipation and for defecation to occur at least three times a week with a soft, formed stool. The initial treatment strategy for constipation nearly always includes the ingestion of more dietary or supplemental fibre. Increased fibre intake improves stool consistency and accelerates colon transit in many individuals and generally provides a safe and inexpensive first‐line approach.42 Increased fluid intake is also frequently recommended. Although this may have value in the dehydrated patient, increasing fluid intake in chronic constipation rarely improves constipation symptoms.8 Likewise, increased physical activity is also recommended without clear evidence of efficacy.8 General non‐pharmacological advice given first line includes information about a normal bowel