Definition and etiology
Constipation is a broad term that is defined as difficult evacuation of feces, infrequent defecation, or inadequate defecation. Our understanding of the etiology of constipation has improved, resulting in an evolving definition. One commonly used definition is based upon bowel frequency of fewer than three stools per week. This definition is based on interviews of factory workers in the United Kingdom that found that 99% of the working population reported a frequency of bowel movements between three per day and three per week. The problem with this definition is that it ignores the symptoms reported by most patients who consider themselves constipated (i.e., straining, hard stools); it does not assist in separating out those patients with disorders of slowed intestinal transit and those with disorders of defecation, and it may not apply to patients who are taking laxatives.
Although physicians and patients often refer to constipation as a single disorder, it should be viewed as a symptom that means different things to different people. In 1987, Sandler and Drossman reported on the bowel habits of more than 1000 adults. The patients were asked how they define the term constipation. Some 52% said “straining at stool,” 44% reported “hard stools,” 34% reported “a sense of wanting to defecate but cannot,” 32% reported “infrequent stools,” 20% reported “abdominal discomfort,” 19% reported “a sense of incomplete evacuation,” and 11% said “spending too much time on the toilet.” Therefore, simply asking a patient whether he or she has constipation is neither sensitive nor specific. However, there appears to be a large percentage of individuals who feel that they have constipation yet do not complain of any symptoms that physicians typically use to define constipation. This difference in definition between patient-centered self-report of constipation and objective criteria indicates that reliance on stringent symptom-based criteria may miss a large population who believe that they have constipation, whether they do or do not, based on those criteria.
Because constipation becomes a problem only when the patient complains of it, and because symptoms of constipation may occur in the absence of any physiologic abnormalities (i.e., stool frequency does not necessarily correlate with transit time), a symptom-based definition still holds some value and has become the standard. This led to the development of the Rome criteria ( ) for functional gastrointestinal disorders, with the most recent version summarized in the Rome IV criteria ( ). These symptom-based criteria are expert consensus guidelines for making the clinical diagnosis of the various types of functional bowel disorders, including constipation. The criteria have become the standard for the definition of constipation.
The Rome IV criteria divide patients complaining of symptoms of constipation into two major groups: those with functional bowel disorders and those with functional anorectal disorders. Functional bowel disorders include (1) functional constipation, (2) irritable bowel syndrome (IBS) with constipation (IBS-C), and (3) opioid-induced constipation. Experts continue to consider the first two disorders as part of a single continuum. Abdominal pain and bloating may be present in subjects with constipation but not be predominant symptoms (i.e., the patient does not meet criteria for IBS). Subjects with functional constipation often complain of fewer than three bowel movements per week, hard or lumpy stools, straining, feeling of incomplete emptying after a bowel movement, a sensation that stool cannot be passed, or a need to press on or around their bottom or vagina to complete a bowel movement. Functional constipation may include patients who demonstrate slowed transit times on colonic transit studies or patients with normal transit or idiopathic constipation, because it is a symptom-based diagnosis. In fact, the latest American Gastroenterological Association (AGA) technical review does not use the term “functional constipation,” because of this subset of patients who have slow transit constipation ( ). Instead, the AGA criteria rely on assessments of colon transit and anorectal function to classify patients with constipation into one of three groups: normal-transit constipation, slow-transit constipation, and pelvic floor dysfunction or defecatory disorders.
The diagnostic criteria for functional constipation are shown in Box 28.1 . Patients with IBS-C have the same symptoms, except that they often have a predominance of abdominal pain. This pain is related to (improved or worsened with) defecation, change in the number of bowel movements, or change in consistency of stools. Some experts have believed that constipation could be broken down into further subtypes based on the reported predominant evacuation symptoms, including IBS-outlet and outlet-type constipation. A subcategory of patients who fulfil criteria for either IBS-C or functional constipation also report one of the following evacuation symptoms: a sensation that stool cannot be passed when having a bowel movement, a need to press on or around their bottom or vagina to try to remove stool to complete a bowel movement, or difficulty relaxing or letting go to allow the stool to come out at least one-fourth of the time. These subtypes are now referred to as functional defecation disorders. The diagnostic criteria for functional defecation disorders are seen in Box 28.2 .
Must fulfill both a criteria:
- 1.
Must include two or more of the following:
Straining >25% of defecations
Lumpy or hard stools (Bristol Stool Form Scale 1–2) >25% of defecations
Sensation of incomplete evacuation >25% of defecations
Sensation of anorectal obstruction/blockage >25% of defecations
Manual maneuvers to facilitate >25% of defecations
Less than three spontaneous bowel movements per week
- 2.
Loose stools are rarely present without the use of laxatives.
- 3.
There are insufficient criteria for irritable bowel syndrome.
Criteria are met for the last 3 months with symptom onset at least 6 months before diagnosis.
Diagnostic criteria a for functional defecation disorders:
- 1.
The patient must satisfy diagnostic criteria for functional constipation and/or irritable bowel syndrome with constipation
- 2.
During repeated attempts to defecate, there must be features of impaired evacuation, as demonstrated by two of the following three tests:
- a.
Abnormal balloon expulsion test
- b.
Abnormal anorectal evacuation pattern with manometry or anal surface electromyography
- c.
Impaired rectal evacuation by imaging
- a.
Subcategories for functional defecation disorders apply to patients who satisfy the following criteria:
- 1.
Inadequate defecatory propulsion: Inadequate propulsive forces as measured with manometry with or without inappropriate contraction of the anal sphincter and/or pelvic floor muscles
- 2.
Dyssynergic defecation: Inappropriate contraction of the pelvic floor as measured with anal surface electromyography or manometry, with adequate propulsive forces during attempted defecation
Criteria fulfilled for the last 3 months with symptom onset at least 6 months before diagnosis.
Normal-transit constipation is probably the most common form of constipation, although this has not been formally studied. In these patients, stool frequency may be normal, but patients feel constipated and may report difficulty with defecation, bloating, abdominal pain, and hard stools. On testing, patients in this group may have increased rectal compliance, reduced rectal sensation, or both ( ). Patients with slow-transit constipation typically have a decreased number of high-amplitude propagated contractions of the bowel. This may result from abnormalities of the myenteric plexus, decreased interstitial cells of Cajal that are required to generate smooth muscle electrical slow wave, diminished excitatory extrinsic nervous input, or extrinsic inhibitory activity ( ). Those with defecation disorders may have normal or slightly slowed transit studies but have preferential storage of stool in the rectum. They also have higher defecatory sensation thresholds and may tolerate higher volumes in the rectum. Based on the Cleveland Clinic experience, outlet-type symptoms of constipation seem to be the predominate subtype seen in patients with other pelvic floor disorders such as pelvic organ prolapse and incontinence. Patients with dyssynergic defecation have paradoxical contraction or failure to relax the pelvic floor muscles during attempts to defecate. Physical examination may reveal a failure to relax the puborectalis or paradoxical contraction during an attempted defecation, and laboratory testing shows evidence of inappropriate contraction or failure of relaxation of the pelvic floor during attempts to defecate. Structural abnormalities are less common but include rectal prolapse and/or intussusception, rectocele, and excessive perineal descent.
The pathophysiology of constipation continues to evolve. Investigators have attempted to examine the relationships between slow transit disorders and external neuropathy conditions, such as spinal cord injury, Parkinson disease, multiple sclerosis, medications, and diabetes. The premise behind these disorders is that the symptoms of constipation result from motor and sensory disturbances, ultimately leading to delayed transit or physiologic disorders of the colon and pelvic floor, and, in women with slow-transit constipation refractory to medical therapy, colonic manometry can identify underlying neuropathy that may warrant colectomy ( ). The primary causes of constipation are disordered regulation of the neuromuscular components within the colon and anorectum, as well as disruption in their corresponding ascending and descending pathways in the brain-gut axis ( ). Patients with slow colonic transit have a resting colonic motility similar to normal controls but have little or no increase in motor activity after meals or stimulation with bisacodyl ( ; ). Neuropathy of the enteric nervous system may also occur in patients with Chagas disease secondary to infection by Trypanosoma cruzi , those with Hirschsprung disease, or those who engage in chronic laxative abuse. Genetic mutations demonstrated in patients with Hirschsprung disease include a mutation in the endothelin B receptor ( ) and an inactivating mutation in the RET protooncogene ( ).
Studies of the pathophysiology of disorders of defecation have examined altered anorectal motor and sensory function. Recently, three patterns of disordered defecation have been recognized that involve impaired anal relaxation at the puborectalis, external anal sphincter, or both ( ). These patterns were identified by studies involving perceptual responses to controlled rectal distension, alterations to visceral sensation, and pudendal nerve terminal motor latencies. Most patients with disorders of defecation suffer from the inability to coordinate the abdominal, rectoanal, and pelvic floor muscles during attempted defecation ( ). For example, there is evidence that dyssynergia of the puborectalis and external anal sphincter muscles during defecation leading to outlet dysfunction and constipation in patients with multiple sclerosis is caused by a spinal lesion. showed that this functional abnormality also occurred in patients with Parkinson disease, and that, in Parkinson disease, it was responsive to dopaminergic medication. showed that interruption of pathways in the spinal cord can result in detrusor-sphincter dyssynergia, and it is therefore likely that paradoxical puborectalis contraction in multiple sclerosis is caused by interruption of spinal pathways by demyelination. The data provide evidence that functional bowel disorders may be more intimately associated with the neurologic system than is commonly thought. Despite these advances, our knowledge of neuroanatomy and its relationship to functional disorders of the bowel remains in its infancy.
Epidemiology
Constipation is a commonly encountered problem in medical practice and is expected to increase dramatically. The US population is becoming older, and more individuals are likely to be living with chronic neurologic disease and to reside in nursing homes. Estimates of incidence and prevalence vary depending upon the definition used (i.e., self-reported constipation or Rome criteria) and the population studied. Few data are available on the incidence of constipation. reported a rate of constipation onset of 40 per 1000 person-years in White residents of a single county in Minnesota. The symptom remission rate was 309 per 1000 person-years. , in a large US epidemiologic study of more than 10,000 individuals, found an overall constipation prevalence of 14.7% in the general population. Worldwide estimates are similar, with 12% of people reporting self-defined constipation ( ). More recently, a systematic review and meta-analysis estimated the global prevalence and risk factors for chronic idiopathic constipation in 41 separate studies across several continents and estimated that the pooled prevalence in all studies was 14% (95% confidence interval: 12%–17%) ( ). The pooled prevalence was largely stable across geographical locations and was slightly lower in South East Asian studies and higher in South American studies.
The global pooled prevalence of chronic idiopathic constipation appears to be higher in women compared with men (17% vs. 9%), and the rates of constipation subtypes in men and women in the United States are as follows: functional constipation 4.6%, IBS-C 2.1%, outlet constipation 4.6%, and IBS-outlet constipation 3.6% ( ; ). Overall, women had higher rates of outlet disorders. However, when constipation subtypes were broken down by gender, the only statistical difference was in women being more likely to have the IBS-outlet subtype of constipation. Most of the studies that stratified by age found consistent trends of increasing prevalence of constipation with age, with significant increases after age 70 years. Interestingly, when stratified constipation subtypes in women by age, the prevalence of constipation actually decreased with increased age.
Most data suggest similar racial differences in the prevalence of constipation, with the average prevalence being 1.17- to 2.89-fold higher in non-Whites than in Whites. Outlet-type constipation was also more prevalent among non-Whites according to data from . In one meta-analysis of six studies, pooled estimates demonstrated an increase in the prevalence of constipation in those of lower socioeconomic status compared with those of higher socioeconomic status ( ).
Because of the high prevalence, constipation consumes substantial health care resources. Constipation is one the five most common physician diagnoses for gastrointestinal disorders. Data from the National Ambulatory Medical Care Survey and the National Hospital Ambulatory Medical Care Survey suggest that ambulatory visits for constipation increased from 4 million visits per year from 1993 to 1996 to almost 8 million visits per year from 2001 to 2004 (0.72% of all ambulatory visits) ( ). The annual direct medical costs for constipation were recently estimated to exceed $230 million, and the costs incurred by women with constipation were double those of women without constipation ( ; ).
Among 300 women presenting to a urogynecology clinic for either pelvic organ prolapse or incontinence, the overall prevalence of constipation was 36%, as defined by the Rome II criteria. When this sample was stratified by subtype, 5% had functional constipation, 19% outlet-type, 5% IBS-C, and 7% IBS-outlet type ( Fig. 28.1 ). Given recent population shifts in North America, constipation and its associated outlet disorders make this a condition with which gynecologists and urologists should be familiar.
Evaluation
Patients who report constipation often have features of both slow-transit disorders and anorectal disorders. When attempting to evaluate constipation, it is convenient to try to separate out these two pathophysiologic mechanisms and tailor treatment accordingly. It is also helpful to distinguish between transient constipation that started at a time of change in dietary habits or lifestyle changes and those that are chronic. At the conclusion of the initial clinical evaluation, it should be possible to classify patients into the following categories ( ; ):
- 1.
Normal-transit constipation with normal colonic transit and defecation
- 2.
Slow-transit constipation, when pelvic floor function is normal and there is evidence of slow transit
- 3.
Defecatory disorders including failure of relaxing the pelvic floor during defecation or descending perineal syndrome
- 4.
Combination of numbers 2 and 3
- 5.
Organic constipation because of mechanical obstruction or side effects of medications
- 6.
Secondary constipation owing to metabolic disorders
A thorough history and physical examination, minimal laboratory tests, colonoscopy, and other diagnostic tests are done as needed based on the history and physical examination.
History
The history begins with clarifying what the patient means when reporting constipation, such as number of stools per week, difficulty expelling stool or a feeling of incomplete defecation, pain with defecation, consistency of stool (including hard or lumpy stools), and duration of the problem. Some patients experience rectal pressure or fullness. Others may need to use their fingers to expel stool or stabilize the vagina or perineum, referred to as splinting, during defecation. They may be embarrassed to admit some of these practices and may need to be encouraged to tell this information. Features such as rectal bleeding in the absence of anal fissures or hemorrhoids, unintended weight loss, and family history of colon cancer should be elicited. Additionally, a dietary history, including questions about the amount of dietary fiber and fluid consumed daily, is necessary.
Objective measures of stool frequency, colonic transit, and anorectal function can also be performed when necessary. The Bristol Stool Form Scale is a useful tool that uses visual images of various forms of stool consistency on a 7-point scale. This scale has been compared against stool transit times and is easily understood by patients ( ; ; ). It may be particularly useful in patients who self-report constipation who have three or more bowel movements per week to establish whether hard or lumpy stools are present.
Ruling out associated medical problems that may lead to secondary constipation ( Box 28.3 ) is important. Constipation is more common in people with neurologic disease, such as multiple sclerosis and spinal cord injury. Diabetes may also be associated with constipation. Recent changes in routine, such as levels of diet and exercise, may contribute to constipation. found that decreased caloric intake favored constipation. Additionally, regular exercise is associated with a reduced risk of constipation ( ; ). In patients with severe constipation and no obvious cause, histories of physical and/or sexual abuse may be found.
Personal Habits
Low physical activity
Low calorie diet
Employment status
Obstructive
Colon
Neoplasm
Benign stricture (i.e., diverticula)
Rectal prolapse
Anal outlet obstruction
Pain (i.e., anal fissure)
Stenosis
Rectocele
Pelvic floor dyssynergia
Medications
Narcotics
Antidepressants
Mineral supplements (i.e., iron, calcium)
Anticholinergics
β blockers, calcium channel blockers
Endocrine
Hypothyroidism
Hypercalcemia
Hypokalemia
Diabetes mellitus
Uremia
Neurologic
Aganglionosis (congenital: Hirschsprung disease; acquired: Chagas disease)
Central nervous system or spinal cord trauma or disease (Parkinson disease, multiple sclerosis)
Pregnancy
Psychiatric Causes
Other
Past surgeries may provide clues and should be elicited. Some debate exists as to whether hysterectomy causes constipation. In 1992, Prior et al. reported on 200 patients who underwent hysterectomy and found that 5% developed IBS-C. In 2004, Altman et al. reported on 120 consecutive patients who underwent either vaginal or abdominal hysterectomy. No statistical difference was present in preoperative and postoperative bowel emptying difficulties or incomplete bowel evacuation.
Physical examination
The physical examination is tailored to the patient. The abdominal examination is usually normal, but masses, palpable stool in the colon, and surgical scars and hernias should be noted. The perineal examination starts with an inspection, looking for anal fissures or abnormalities. Asking the patient to strain may demonstrate perineal descent, widening of the perineal body, rectal prolapse, or a rectocele protruding into the vagina. Digital examination rules out fecal impaction, anal stenosis or stricture, external or internal rectal prolapse, pelvic or rectal masses, and rectocele. The examiner should note the consistency of stool in the rectum. The tone of the levator ani muscles on vaginal and rectal examination should be assessed at relaxation and with straining. Paradoxical contraction may be suspected if a failure to relax the puborectalis is noted when the patient is asked to simulate defecation. These patients often have a history of excessive straining before elimination. Even soft stools and enema fluid are difficult to pass. A carefully performed digital rectal examination has a high yield of detecting dyssynergia in patients with chronic constipation. The high specificity (87%) and positive predictive value (97%) make digital rectal examination an ideal test that can be used to diagnose dyssynergia in a patient with chronic constipation and symptoms of difficult defecation ( ). Pain on the border of the puborectalis is a feature of some anorectal pain disorders with associated pelvic muscle spasm.
Few clinicians would dispute the association between vaginal prolapse and symptoms of constipation, although a direct relationship between the two is not clear. In 1998, Weber et al. described 143 women who completed a questionnaire assessment of bowel function and underwent standardized examination using the Pelvic Organ Prolapse Quantification method. In 26.6% it was rare to require straining to have a bowel movement, in 49.6% straining was sometimes required, in 14% straining was usually required, and in 9.8% straining was always required. Some 31% needed to help stool come out by pushing with a finger in the vagina or rectum. Severity of prolapse was not related to severity of bowel dysfunction. In a Swedish population of 491 women, when a rectocele was present 18% reported problems with emptying the bowel at defecation compared with 13% in the nonrectocele group ( ). However, constipation was not related to prolapse in this population.
Laboratory evaluation
Blood work to assess a complete blood count, calcium, and thyroid-stimulating hormone should be carried out if a problem is suspected. Although these studies are often performed, their diagnostic utility and cost-effectiveness have not been evaluated and are likely low ( ).
Testing
Further testing depends on the severity of symptoms and findings on physical examination. At this stage in the management of constipation, the majority of patients require no further testing, and the physician can proceed to medical therapy. Patients older than age 50 years (≥45 years in Black people) should have a screening colonoscopy, based on national recommendations. This examination rules out neoplasms, a solitary rectal ulcer (erythema or ulceration on the lower anterior rectal wall thought to be from trauma secondary to internal rectal prolapse), or melanosis coli (brown-black discoloration of the mucosa from chronic use of certain laxatives).
A therapeutic trial of fiber is warranted if no cause has been found. Patients who do not respond may require further diagnostic evaluation to identify the subgroups of constipation. The tests chosen depends on patient characteristics and severity of symptoms. Testing is useful to distinguish between patients with defecatory dysfunction and slow transit. Three main physiologic tests can be used to assess defecatory dysfunction: balloon expulsion test, anorectal manometry, and colon transit studies. In patients with symptoms that are highly suggestive of pelvic floor dysfunction, anorectal testing with rectal balloon expulsion test and anorectal manometry are first considerations and may be considered even before trying laxatives ( ).
Balloon expulsion test.
The balloon expulsion test has been used to exclude patients with constipation suspected of having defecatory disorders. Normally, rectal distension is simulated with an air- or fluid-filled balloon, usually a lubricated latex condom, in the rectum. This is tied to a catheter that is introduced into the rectum. Fluid is instilled into the balloon, and total volume is measured when the patient has a sustained feeling of necessity to defecate. The time required to expel the rectal balloon in the seated position is measured. Patients should be able to expel the balloon in less than 1 minute to up to 5 minutes ( ; ). A 50-mL balloon filled with water can usually be expelled in 1 to 2 minutes. In 2004, Minguez et al. identified patients with functional constipation, both with and without pelvic floor dyssynergia. Balloon testing was performed, showing a specificity and negative predictive value of balloon testing for excluding defecation disorders of 89% and 97%, respectively. This may be a useful screening test in clinical practice because patients with a normal balloon expulsion test result, independent of the frequency of defecatory symptoms, do not need other functional studies that are more expensive and difficult to perform to rule out pelvic floor dyssynergia.
Anorectal manometry testing.
In the evaluation of constipation, manometry is most helpful in excluding Hirschsprung disease by the presence of a normal rectoanal inhibitory reflex and a supporting clinical impression of defecatory disorders, as evidenced by high anal resting pressures, typically 90 mm Hg or more, with relatively little voluntary augmentation suggestive of a nonrelaxing pelvic floor ( ). Brief distension of the manometry balloon normally leads to reflexive internal sphincter relaxation and external sphincter contraction. This is called the rectal anal inhibitory reflex. In patients with Hirschsprung disease, this does not occur. Compliance of the rectum can be calculated by measuring the sensitivity and maximal volume tolerated in a fluid-filled balloon. An increased compliance can be seen in patients with constipation and signals a megarectum or insensitive rectum ( ). Manometry may also be therapeutically used for patients with constipation in anal manometry–assisted biofeedback, as discussed later.
Colon transit testing.
The colonic transit study is an important test to evaluate the colon for slow transit but is not required nor justified in all patients for the evaluation of constipation ( ). Patients must stop all laxative use 48 hours before the study. They should also consume a high-fiber diet (30 g daily) and refrain from using enemas. Many variations of this study are known, but basically patients consume a commercially-prepared capsule that contains a certain number of radiopaque markers. The Hinton technique involves ingesting a capsule containing 24 radiopaque markers; normally, less than five markers should remain in the colon on an abdominal radiography 5 days later ( ). Another method involves ingesting a capsule containing 24 markers on days 1, 2, and 3 and then counting the markers remaining on a plain abdominal radiograph on days 4 and 7. Eight or fewer markers remaining in the colon is considered normal. Some clinicians divide the colon into right, left, and rectosigmoid to determine the transit time of each segment. This allows distinction between whole-gut dysmotility, as seen by evenly distributed markers throughout the colon to the rectum, versus anal outlet obstruction, in which the markers progress quickly through the colon and are held up in the rectal sigmoid region. In another pattern, markers proceed through the colon, accumulate in the left colon, and stop. This signals left colonic dysfunction.
Barium and magnetic resonance defecography.
The diagnostic role of defecography remains unclear, but this test is useful when anorectal testing results are inconsistent with the clinical impression and/or to identify anatomic abnormalities ( ; ). See for a detailed demonstration of the indications, technique, and normal and abnormal findings of defecography. Defecography is performed by placing a paste of contrast material into the rectum to simulate stool. Radiographs are taken at rest and during straining. During the examination, the patient sits on a commode behind a curtain, and fluoroscopy is performed to obtain the pictures. The items examined include the angle between the anal canal and rectum at rest, strain, and squeeze. The ability to evacuate contrast material, presence of a rectocele, and evidence of intussusception should be noted. During normal defecation, the anal canal becomes straighter, which, in turn, increases the angle. If this does not occur, the puborectalis muscle may be inappropriately contracting and may prohibit the expulsion of the contrast (and stool). The amount of descent of the perineum is noted, because this may be associated with anal outlet obstruction and constipation. Additionally, enfolding of the walls of the rectum with defecation, as is seen with internal prolapse, is evaluated. Defecating proctogram may be useful in establishing the diagnosis of internal rectal prolapse or rectoceles. This study helps delineate the rectoceles that are displaced anteriorly, not fully emptying, and may require repair ( Fig. 28.2 ). Also, enteroceles and sigmoidoceles can be seen. It should be noted that this test is embarrassing for the patient, and complicated and unstandardized for the radiologist to perform. Therefore, the results may not always demonstrate the abnormality or may not be totally accurate. Defecography is useful for assessing rectal evacuation. It provides functional or morphologic features of the defecatory maneuver. However, there is a poor correlation between defecography and electromyography or manometry for diagnosing pelvic floor dyssynergia.
