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 habit, ingestion of a healthy, fibre‐rich diet (20–30 g per day), taking advantage of the meal‐related increase in colonic motor activity, and avoiding postponing defecation. Given the strong association of constipation in older people with medication use, medications should be eliminated or adjusted, substituting less‐constipating alternatives where possible. Medications used in the treatment of constipation are listed in Table 20.4.
Table 20.4 Medications used in the treatment of constipation.
| Agent | Daily dose |
|---|---|
| Bulking agents | |
| Bran (wheat or oat) | 4–10 g |
| Psyllium | 3–6 g |
| Calcium polycarbophil | 2–4 g |
| Hydrolysed guar gum | 3–6 g |
| Methylcellulose | 2–4 g |
| Osmotic | |
| Polyethylene glycol (PEG) | 17–34 g |
| Lactulose | 10–40 g |
| Magnesium salts | Generally avoided in elders |
| Sorbitol 70% solution | 15–60 ml |
| Stimulant | |
| Senna | 15 mg |
| Bisacodyl | 5–10 mg |
| Sodium picosulfate | 5–10 mg |
| Other | |
| Lubiprostone | 8–24 μg b.i.d. |
| Linaclotide | 290 μg |
| Prucalopride | 1–2 mg |
| Methylnaltrexone | Weight‐based dosing |
| Probiotics | Bifidobacterium infantis 1 capsule, yoghurt 8–16 oz daily |
Pharmacological management
Bulking agents
Bulking agents commonly used include wheat or oat bran, psyllium (ispaghula), calcium polycarbophil, carboxymethylcellulose, and partially hydrolysed guar gum. A recent systematic review showed fibre supplementation to be beneficial in mild to moderate chronic constipation and in IBS.43 Whilst taking fibre supplements, ensure that patients are drinking an adequate amount of water to avoid hard and bulky stools. In patients with faecal impaction, those who are bedbound, or with minimal fluid intake, fibre supplements should be avoided.43 Side effects of fibre supplements include bloating and increased flatulence.
Stool softeners
Stool softeners such as dioctyl sodium sulfosuccinate and dioctyl calcium sulfosuccinate (docusate sodium) are reported to soften the stool, easing defecation. Despite the widespread use of these agents, there are no randomized controlled trials showing efficacy.44 One study comparing dioctyl sodium sulfosuccinate with placebo showed no improvement in stool frequency or consistency.45 Another study comparing dioctyl sodium sulfosuccinate with psyllium found psyllium to be superior.46 The therapeutic use of stool softeners appears limited for the treatment of chronic constipation.
Osmotic laxatives
Osmotic
