Introduction
Constipation is the most common bowel complaint in the United States, with an estimated prevalence of 2% to 27%. The wide range is attributed to the variety of definitions of constipation used by patients and physicians. The Rome Criteria, which were developed to provide a standardized definition, require two or more of the following conditions for at least 3 months: straining more than 25% of the time, hard stools for more than 25% of the time, incomplete evacuation more than 25% of the time, and/or two or fewer bowel movements per week. Using these criteria, the estimated prevalence of constipation is 15%, and half the persons affected have obstructed defecation syndrome. Other standardized definitions exist, such as the one by Cleveland Clinic Florida.
Women are two to three more times likely to have constipation than are men. The National Health and Nutrition Examination Survey reported a 10.2% prevalence of constipation in women and a 4.0% prevalence in men. Constipated patients reported eating fewer fruits and vegetables and drinking more coffee or tea. The incidence of constipation increases with age.
Causes
Causes of constipation may be mechanical, functional, or a combination of both. Nonmechanical causes with a normal caliber colon can include reduced peristalsis as a result of immobility, use of drugs, increasing age, metabolic disorders, endocrine disorders, neurologic disease, dietary deficiencies, physical or sexual abuse, or just slow transit. When constipation is associated with a dilated colon, causes include Hirschsprung disease, Chagas disease, and Ogilvie syndrome. Anatomic factors affecting defecation include rectal inertia, anismus, and paradoxical internal sphincter contraction. Rectal prolapse, descending perineum syndrome, and rectocele are related findings.
Sometimes an episode of gastroenteritis will result in continued bowel symptoms long after the offending bacteria or virus has been eliminated. The cause of constipation in these patients is unknown, but up to 25% of cases of irritable bowel syndrome (IBS) may be due to this problem. Chronic treatment with opioids is a specific and common cause of colonic inertia due to activation of central μ-opioid receptors in the gastrointestinal tract. Opioid-induced constipation is associated with increased use of health care dollars and decreased quality of life. Laxatives alone are usually insufficient to treat this condition because they do not target the underlying cause of the constipation (μ-opioid receptor activation). Methylnaltrexone bromide is a peripherally acting μ-opioid receptor antagonist, and data support its use for opioid-induced constipation with a favorable tolerance profile. Rare cases of chronic pseudo-obstruction, an unusual disorder of the gastrointestinal tract characterized by impaired peristalsis that can lead to constipation or diarrhea, also have been reported. Patients present with symptoms of bowel obstruction, but no mechanical cause is identified. Subgroups of this rare disorder include neuropathy, myopathy, or mesenchymopathy, with neuropathy the most prevalent. Forty percent of cases are primary and 60% are secondary. This disease is normally progressive. Treatment includes ruling out obstruction, evaluating for myopathy or neuropathy, and providing nutritional support.
Classifying Constipation
Clinically, patients with constipation are classified into several categories:
- 1.
Slow transit (colonic inertia)
- 2.
Irritable bowel syndrome—constipation predominant (IBS-C)
- 3.
Pelvic floor dysfunction (obstructed defecation syndrome)
- 4.
Mixed slow transit/pelvic floor disorder
Colonic inertia is frequently associated with symptoms since childhood and laxative dependency. IBS-C is usually accompanied by abdominal pain (which is often relieved by defecation) and irregular bowel habits. Pelvic floor dysfunction or obstructed defecation syndrome refers to a symptom complex of prolonged straining, the sensation of incomplete evacuation, and the need for digital manipulation.
Assessment
History
History is the key to the diagnosis of constipation, and taking time to develop a full picture of the patient’s symptoms in the setting of his or her overall health and lifestyle is worthwhile. Obtaining a detailed account of what constipation means to each individual patient is very important. Information should be obtained about stool frequency, consistency, size, and the presence of urgency/straining/incomplete evacuation. The Bristol Stool Form Scale (BSFS) can provide a visual and numeric reference as a rough estimate of colonic transit. Lower scale numbers on the BSFS mean slower transit. The BSFS is scored between 1 and 7 as follows:
- 1.
Small hard lumps, like nuts
- 2.
Sausagelike but lumpy
- 3.
Sausagelike or snakelike with a cracked surface
- 4.
Sausagelike or snakelike, smooth and soft
- 5.
Soft blobs with clear-cut edges
- 6.
Fluffy pieces with ragged edges (a mushy stool)
- 7.
Watery stool
The age at which symptoms began should be documented. Constipation from infancy raises the possibility of Hirschsprung disease. One should ask about typical dietary choices, focusing on fiber content and supplementation, and review the effect of fiber supplementation on constipation. Some but not all patients find fiber supplementation helpful. The patient should be asked about other symptoms such as abdominal pain/discomfort/bloating and the effect of defecation on these symptoms, which may be suggestive of other disease or IBS-C. The following histories should be obtained and critically assessed: detailed medical (including diabetes, hypothyroidism, hypercalcemia, connective tissue disorder, and neurologic disease), family, dietary, psychiatric, surgical, obstetric, and drug (including opiates, iron, antiparkinsonian drugs, anticholinergic drugs, calcium channel blockers, and antidepressants). Urinary symptoms and sexual dysfunction may be important because multicompartment pelvic floor disease is common. A history of sexual/physical abuse, eating disorders, or psychiatric illnesses may be an important factor in the onset and chronicity of the constipation.
Several validated constipation questionnaires differentiate constipated patients from healthy volunteers. The constipation severity instrument is one example. It provides a short, self-reported assessment of constipation severity and identifies subtypes of constipation. The total scale ranges from 0 to 73, with higher scores associated with more severe symptoms.
Physical Examination
A thorough physical examination includes a generalized assessment, with particular emphasis on abdominal, neurologic, anorectal, perineal, and vaginal examinations. Some important points of anal and pelvic examinations are as follows:
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On anorectal examination, the status of the rectum should be noted—capacious, empty, or full of stool. The sphincter muscle tone is documented. A patulous anus may indicate neurologic injury or injury as a consequence of mechanical factors, such as long-standing rectal prolapse. An unusually tight anus (anismus) may be a cause of incomplete defecation and anal pain. Sphincter coordination is examined when patients are asked to squeeze, relax, and then push. With paradoxical puborectalis contraction, the pelvic floor muscle contracts instead of relaxing when the patient strains down or attempts to defecate.
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Rectal prolapse can cause constipation but also fecal incontinence. When rectal prolapse is suspected but not seen on examination, the patient should be asked to bear down or sit on the toilet to simulate defecation.
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A rectocele is defined as a herniation of the anterior rectal wall into the vagina. Rectocele severity can be expressed as stages I to IV and depends on the maximal protrusion inferiorly with reference to the hymeneal ring. A rectocele sometimes develops secondarily to obstructed defecation, and pelvic floor assessment for paradox is important. A large rectocele sometimes can be seen just by inspecting the perineum, with the anterior wall of the rectum protruding through the posterior wall of the vagina. One can see a size increase when the patient bears down.
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Rectoanal intussusception, also called internal intussusception, internal prolapse of the rectum, and occult rectal prolapse, is a funnel-shaped infolding of the rectum that can occur with Valsalva maneuvers. It is thought to be the start of rectal prolapse. Descent of the perineum beyond the level of the ischial tuberosities is suggestive of perineal descent.
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Anoscopy can identify mucosal abnormalities and rectoanal intussusception. When the patient is asked to bear down as the anoscope is removed, the redundant rectal mucosa can be seen impacting into the anus.
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Gynecologic examination focuses on an examination of the posterior vaginal wall. Prolapse should be noted and staged based on the Pelvic Organ Prolapse Quantification System. The physical examination for patients with IBS-C and motility disorders is frequently normal.
Investigations
With regard to blood work, an evaluation for electrolyte abnormalities (calcium), diabetes, and thyroid function tests is basic, especially if obstructed defecation has been ruled out.
A colonoscopy should always be performed to exclude mechanical causes of obstruction such as a stricture, cancer, or diverticular disease. Sigmoid colon adhesions after pelvic surgery in women can produce significant obstruction, with symptoms that are often misdiagnosed as IBS. During colonoscopy, insertion through the sigmoid is difficult and reproduces the pain and bloating with which the patient has presented. A sigmoid colectomy should be considered.
Anal manometry provides information on resting and squeeze anal sphincter pressures, the presence of rectoanal inhibitory reflex (RAIR), rectal sensation, rectal compliance, and balloon expulsion. Assessment of rectal sensation is performed by determining the lowest volume that evokes a sensation of rectal filling and the maximum tolerable volume. This assessment is important in patients with fecal incontinence but also in patients with rectal hyposensitivity. Constipated patients may demonstrate internal sphincter hypertonia. The presence of a RAIR excludes Hirschsprung disease (although its absence is not proof of Hirschsprung disease; other conditions, such as megarectum, can account for the absence of a RAIR). Balloon expulsion assesses the ability to evacuate and can reliably diagnose pelvic floor outlet obstruction (i.e., the inability to expel a 50- to 100-mL balloon in less than 1 minute).
Electromyography aids in the diagnosis of paradoxical or nonrelaxing puborectalis muscle by demonstrating activation of the puborectalis during defecation.
Transit marker studies or nuclear medicine transit studies identify colonic dysmotility. With the sitz marker test, the patient ingests one or two capsules containing 24 small plastic markers each (rings and panels). Transit time is estimated based on the rate at which these markers are eliminated. We instruct patients to take one capsule early Sunday morning. The patient then undergoes serial abdominal radiographs, with one on Monday morning, the next on Wednesday, and the final on Friday. Different institutions use different practices, therefore the radiologist should verify and report how many and when the capsules were taken. Patients are told to eat two servings of over-the-counter high-fiber products daily in addition to their usual diet (30 g fiber total) and not to use laxatives. Colonic transit is normal if 80% (38 of 48) of the rings have been eliminated by day 5. The distribution of the markers throughout the colon is also important. If the markers tend to accumulate in the rectum, then outlet obstruction is likely. If the markers remain scattered throughout the colon and more than 20% of the markers remain on the fifth day, then colonic inertia is the diagnosis ( Fig. 70-1 ).
