Gastroenterology Hepatology

Approach to the patient with constipation

Overview

A clear distinction must be established between acute, episodic constipation and chronic constipation.

Acute constipation is experienced by nearly every person at some point and can be simply described as self-limited difficult or infrequent defecation.

Chronic constipation is difficult defecation experienced for more than 12 weeks, which need not be consecutive, that is characterized by multiple symptoms such as straining, a sense of incomplete evacuation, a sense of anorectal obstruction, and bloating. Chronic constipation is a common gastrointestinal disorder with a prevalence of between 12% to 19%, although only about 25% of individuals with chronic constipation will see a healthcare provider specifically for their constipation symptoms. Chronic constipation demonstrates an inverse relationship with socioeconomic status and educational background. It is more common in women than men and affects all age groups.

In the past, approaches to define constipation have included using (1) symptoms such as straining, hard stools, infrequency, and scybala, among others; (2) parameters of defecation outside of the 95th percentile of normal; (3) and/or physiologic evidence of prolonged whole gut or colonic transit.

The Rome III Committee on Functional Gastrointestinal Disorders set criteria for the definition and diagnosis of chronic constipation that include concepts of both duration of symptoms (12 weeks or more), as well as symptoms. According to Rome III guidelines, chronic constipation must include two or more of the following: (1) straining during at least 25% of defecations, (2) lumpy or hard stools in at least 25% of defecations, (3) sensation of incomplete evacuation for at least 25% of defecations, (4) sensation of anorectal obstruction, (5) manual maneuvers to facilitate at least 25% of defecations, and/or (6) fewer than three defecations per week. Additionally, there should be insufficient criteria for irritable bowel syndrome (IBS), and loose stools are rarely present without the use of laxative therapies. These criteria should be fulfilled for the previous 3 months with symptom onset at least 6 months prior to the diagnosis.

Differentiating chronic constipation from IBS with constipation can be difficult. Strictly speaking, the primary differentiating factor between the two conditions is the presence of abdominal pain or discomfort associated with altered bowel habits in IBS. It should be realized, however, that patients with chronic constipation may experience abdominal pain or discomfort and that these conditions likely exist on a continuum with significant overlap.

The economic impact of constipation is substantial. Constipation is among the top 5 diagnoses among outpatient primary care clinic visits and the direct costs associated with constipation have been estimated to exceed $200 million. The total costs, including indirect costs such as absenteeism and presenteeism, of constipation have been estimated to be as high as $6.9 billion. From the late 1950s to mid-1980s, the rates of medical visits for constipation remained unchanged; however, more recent analyses examining trends from the 1990s to 2004 suggested that visits for constipation were increasing among pediatric populations but remaining stable for adults, with some decreases in the proportion of medical visits for constipation with adult primary care providers.

Also Known as: Chronic idiopathic constipation, functional constipation, obstipation, pelvic floor dysfunction, anismus

What disease states can produce this sign or symptom?

Multiple disease states can cause the symptom of constipation, ranging from trivial conditions to life-threatening physiological disturbances. Generally, the differential diagnosis should include large categories of possible etiologies such as functional constipation disorders, including chronic idiopathic constipation or irritable bowel syndrome with constipation, metabolic disturbances, abnormalities in fluid balance or nutrition, obstructing lesions of the lower GI tract, or neuromuscular disorders. Iatrogenic constipation is also an important consideration.

Common causes of constipation

  • – Inadequate fiber in the diet

  • – Anorectal disorders such as hemorrhoids, anal fissures, pelvic floor dysfunction, anorectal masses or lesions

  • – Neurologic conditions such as diabetic neuropathy, Hirschsprung's disease, Parkinson's, multiple sclerosis

  • – Metabolic abnormalities such as thyroid disease, diabetes, hypercalcemia

  • – Iatrogenic: opiate pain medications, antidepressants, iron supplementation, antacids, certain antihypertensives

  • – Pregnancy

  • – Eating disorders

  • – Colonic obstruction: masses, strictures

  • – Delayed colonic transit

The exact cause of chronic idiopathic constipation often remains unknown. It is important to realize that the colon is responsible for multiple functions that are related to stool formation. These functions include mixing of the luminal contents, fermenting, and salvaging carbohydrates, reabsorption of water from the effluent to form stool, promoting muscular contractions that push stool in a caudal direction, and storage of the stool bolus for evacuation. These functions appear to be primarily accomplished in different sections of the colon (proximal, distal, and rectosigmoid) and are mediated by different, and poorly understood, mechanisms.

When organic disease is confidently excluded, chronic idiopathic constipation can be divided into three primary categories of decreasing prevalence: (1) normal transit constipation, (2) pelvic floor dysfunction, and (3) slow transit constipation. It is also important to realize that there can be overlap among these subtypes within individual patients, such that pelvic floor dysfunction can coexist with the other two subtypes of chronic constipation.

Normal transit constipation accounts for approximately 80% of chronic idiopathic constipation. As the name implies, gastrointestinal transit, specifically that of the colon, is normal in this subtype of chronic constipation. Pelvic floor dysfunction occurs in approximately 15% of patients with chronic constipation. Pelvic floor dysfunction is a condition in which patients are unable to produce the required coordinated efforts of abdominal, pelvic floor, and recto-anal muscle contractions and relaxations required to produce a successful, complete defecation event. In two-thirds of patients with pelvic floor dysfunction, the abnormalities appear to be acquired, whereas one-third of patients report difficulties since childhood, implying that this latter group never learned how to coordinate a bowel movement during childhood toilet training. Delayed or slow transit constipation is thought to be present in approximately 2% to 5% of patients with chronic idiopathic constipation.

Epidemiology of chronic constipation

Although the estimates of chronic constipation population prevalence of 10% to 15% have been replicated in multiple countries, little is known regarding the incidence of chronic constipation. One study of non-elderly patients in Minnesota found an incidence rate of 50/1000 person years, whereas another study evaluating nursing home residents found an incidence rate of 7% over 3 months; so clearly, incidence of chronic constipation will vary depending on the population being studied.

Constipation is a costly disorder, responsible for more than 2.5 million healthcare-related visits per annum, 90,000 hospitalizations, and hundreds of millions of dollars spent on laxative therapies every year. Most patients with chronic constipation do not seek medical attention for the condition. In one study from Canada, only 34% of individuals who reported constipation had seen a physician for their symptoms. Additionally, most patients will see their primary care provider; only 4% see a gastroenterologist for their constipation symptoms.

Risk factors for constipation

There are multiple risk factors that have been associated with constipation. The most widely recognized risk factors include female sex, extremes of age, non-Caucasian ethnicity, and socio-economic status. Diet, activity, and lifestyle may also play a role in the development of constipation.

Women are more than twice as likely as men to be diagnosed with chronic constipation. The exact reasons for this remain unclear, but hormonal differences and their effects on gastrointestinal motility, as well as the obvious anatomic differences between the sexes, have been implicated. Anorectal dysfunction subsequent to childbirth may also be an important arbiter of this phenomenon.

There is controversy regarding age as a risk factor for constipation, but most studies support the assertion that chronic constipation is associated with increasing age. Constipation in the elderly appears to be more commonly characterized by straining and hard stools than with decreased stool frequency. Constipation is a pervasive issue with nursing home residents and hospitalized patients. Possible reasons for the apparent increase in constipation in the elderly include decreased oral intake, decreased physical activity, weakening of the abdominal muscles, and, often, medication side effects. Constipation is also seen frequently in children less than 4 years of age. The reasons for this pattern are unclear, but the emergence and familiarity with toilet training and body functions likely play a prominent role.

Constipation is more common in non-Caucasians in the United States and is also more common in subjects with lower income status. Studies evaluating diet and constipation have found that higher intake of fiber and physical activity is associated with lower rates of constipation.

What urgent or emergent measures should be initiated even before the diagnosis is established?

Exclude intestinal obstruction.

What is the appropriate initial diagnostic approach to identify the specific underlying disease?

Shown in Figure 1is a diagnostic algorithm for the evaluation of chronic constipation.

Figure 1

Diagnostic algorithm for chronic constipation.

The first step in diagnosing, categorizing, and managing constipation is to determine whether the patient is describing acute, intermittent symptoms or chronic, recurrent symptoms. Patients with acute or intermittent constipation have, by definition, less than 12 weeks of symptoms that are short-lived and resolve either spontaneously or with relatively simple and noninvasive interventions. These individuals rarely seek medical attention for these complaints, but one should remain cognizant that acute constipation symptoms can be the presenting symptoms of other, more ominous conditions. Diagnostic testing is not recommended for patients with acute, intermittent constipation.

Chronic constipation should be present for more than 12 weeks and, especially in medical consulters, is often resistant to satisfactory remediation with lifestyle modifications or over-the-counter medications. Once constipation has been classified as chronic, the clinician should attempt to further classify the diagnosis as either primary constipation or secondary constipation. Secondary constipation is simply constipation that is secondary to another condition or medication. Primary constipation can be further classified into normal transit constipation, pelvic floor dysfunction (anorectal disorders), or slow transit constipation.

The Bristol Stool Form Scale (Figure 2) can be a helpful guide for patients with constipation. Normal stool form includes types 3 and 4, whereas stool forms 1 and 2 are considered consistent with constipated stools. Type 1 stool form corresponds to the classic "scybalous" stool. The Bristol Stool Form Scale correlates to some degree with colonic transit time and stool water content.

Figure 2

Bristol Stool Form Scale.

It is important to exclude organic disease in patients with symptoms of constipation. Generally, this involves performing a physical examination looking for signs and symptoms of potential metabolic or physiologic causes of constipation.

The digital rectal exam should be a mandatory part of this examination and should include an assessment of the perianal sensation, rectal tone and perineal descent with straining. Blood tests should be obtained, including thyroid function tests (TFT), complete blood count (CBC), metabolic panels, calcium levels, and glucose if the clinical scenario suggests that constipation symptoms may be arising from an inflammatory, neoplastic, metabolic, neurologic, or other systemic abnormality. In patients with typical constipation symptoms who do not endorse alarm features suggestive of underlying systemic disease, the routine use of general diagnostic tests such as these have a low diagnostic yield. Diagnostic tests should be carefully considered and based on the pretest probability of disease, the costs and invasiveness of the test, and the possible risks/benefits deriving from test results.

Routine colonoscopy is not recommended in patients with the symptoms of constipation without alarm features such as rectal bleeding, weight loss, or a strong suspicion of obstruction. Colonoscopy should be considered/obtained in patients of colorectal cancer screening age who present with constipation symptoms if it has not been done within the previous 5 to 10 years.

Secondary constipation

Multiple systemic disorders can present with constipation as a prominent symptom. These include, but are not limited to, diabetes mellitus, hypercalcemia, neurologic disorder's such as Parkinson's disease, multiple sclerosis, spinal or sacral cord lesions, myopathic conditions such as muscular dystrophies or systemic sclerosis, neuropathic diseases such as anganglionosis, and psychological disturbances such as major depression and eating disorders.

Constipation as a side effect to medications is probably the most common cause of secondary constipation, and a careful history of prescribed and over-the-counter medications and supplements should be obtained with every patient undergoing evaluation for chronic constipation (Table I).

Table I.

Secondary causes of constipation
Medications
Opiates
Anticholinergic agents
Anticonvulsants
NSAIDs
Antacids
Calcium or iron supplements
Calcium channel blockers
Cholesterol binding agents
Metabolic disturbances
Diabetes mellitus
Hypercalcemia/hypokalemia
Hyper/hypothyroidism
Panhypopituitarism
Porphyria
Pregnancy
Mechanical obstruction
Colorectal cancer
Anal stenosis
Hirschsprung's disease
Rectocele
Extrinsic compression
Neurologic and myopathic disorders
Amyloidosis
Parkinson's
Autonomic neuropathy
Shy-Drager syndrome
Systemic sclerosis
Multiple sclerosis
Dermatomyositis
Muscular dystrophy
Spinal/sacral cord trauma or compression
Chagas disease
Pseudo-obstruction
CVA

What is the diagnostic approach if this initial evaluation fails to identify the cause?

Diagnostic approaches include the following:

  • – Colonic marker studies

  • – Balloon expulsion test

  • – Anorectal manometry

  • – Barium or MR defecography

  • – Wireless motility capsule

Colonic marker studies

A colonic marker study aids in the evaluation of colonic transit time. Normal colonic transit time is less than 72 hours and mean transit time is approximately 36 hours. In a colonic marker study, a gelatin capsule with 24 radiopaque markers is ingested and an abdominal X-ray is obtained approximately 5 days after ingestion.

Retention of more than 20% of the markers is indicative of delayed colonic transit. Prior to the examination, patients should be maintained on a high fiber diet and should abstain from laxatives, enemas, or other medications that can affect bowel function. Clinicians should realize that colonic marker studies are most helpful if they show marker retention in the right or transverse colon.

Multiple protocols are available to accurately characterize regional colonic transit but these protocols generally require additional radiation exposure. Retained markers in the sigmoid or rectum may be indicative of anorectal dysfunction so colonic marker studies that demonstrate retention solely in the recto-sigmoid should be interpreted with caution.

Balloon expulsion tests

Balloon expulsion tests help to identify patients with pelvic floor dysfunction. In this test, a balloon is inserted into the rectum and inflated with 50 to 60 mL of water. A 200 gram weight is added to the end of the balloon and the patient is asked to evacuate the balloon. Failure to do so within 120 seconds is indicative of pelvic floor dysfunction.

Anorectal manometry

Anorectal manometry (ARM) is performed with either a solid-state or water-perfused pressure catheter that is placed into the rectum and slowly withdrawn through the various high pressure zones comprised of the anorectal sphincters. ARM can provide useful information such as the maximum attainable pressures and resting squeeze pressures of the anal sphincters, the characterization of anal sphincter relaxation in response to balloon distention in the rectum, rectal sensation, and the ability of the anal sphincter to relax during straining.

Defecography

Defecography is performed by obtaining still or fluoroscopic images of a patient holding and evacuating thickened barium after it has been instilled into the rectum. This test has fallen out of favor with many radiologists and was never popular with patients. Nevertheless, important information regarding the rate and completeness of evacuation, the anorectal angle, and the presence of large structural abnormalities such as a rectocele can be obtained.

Wireless motility capsule

A wireless motility capsule is a swallowed capsule that contains sensors that will measure transit time, temperature, and pH. Measures from wireless motility capsules permit the measurement of gut motility without the use of radiation and have been shown to correlate well with colonic marker studies.

Pathophysiology of chronic constipation

Normal transit constipation

The functions of the colon are primarily to facilitate absorption of water and electrolytes and to eliminate waste in the form of feces. Activity of colonic muscle permits mixing of luminal contents, allowing contact with the colonic mucosa and reabsorption of water. It also allows the colon to store feces between defecations and propels feces toward the anorectum.

Typical mean colonic transit time is approximately 36 hours and can demonstrate differential rates in various anatomic regions of the colon, typically faster in the right colon. This variation may in part be due to different rates of high amplitude propagating contractions.

As the name would imply, normal transit constipation is marked by normal colonic transit and no anorectal dysfunction. Stool travels along the colon at a normal rate. Although these patients can demonstrate abnormalities in rectal compliance or sensation, most are normal when subjected to physiologic testing. Normal transit constipation represents approximately 80% of chronic constipation.

Pelvic floor dysfunction

Multiple terms have been used to describe pelvic floor dysfunction: these terms include animus, pelvic floor dyssynergia, spastic pelvic floor syndrome, obstructive defecation, or outlet obstruction. These disorders are present when there is difficulty in coordinating the neuromuscular actions of pelvic floor and abdominal muscles to achieve a satisfactory bowel movement.

Pelvic floor dysfunction accounts for approximately 15% of chronic constipation. Patients with this etiology most often complain of severe straining, using digital manipulation to defecate or disimpact, and a sense of incomplete evacuation; however, these symptoms are not terribly helpful in distinguishing pelvic floor dysfunction from other types of chronic constipation.

Pelvic floor dysfunction can also be present when there is a large rectocele if the rectocele demonstrates preferential filling on defecography. These disorders are acquired in approximately two-thirds of patients as adults and present since childhood in one-third, possibly because of ineffective toilet training. Pelvic floor dysfunction is best identified with ARM and some form of defecation evaluation such as barium or MR defecography.

Slow transit constipation

Patients with slow transit constipation have significantly delayed colonic transit as the primary cause of their chronic constipation and are typically women reporting infrequent bowel movements (<1 per week). They will often endorse other symptoms such as malaise, bloating, and fatigue.

Colonic transit studies in patients with slow transit constipation have revealed delayed right colon emptying and decreased frequency of high amplitude propagated contractions. Patients with delayed colonic transit will often fail to experience a gastrocolic reflex and may not respond to stimulant laxatives.

Treatment options

Normal transit constipation

Stool softeners such as docusate sodium and docusate calcium have little to no evidence to support their use as therapies for chronic constipation. These agents ostensibly work as detergents and stimulate fluid secretion in the small and large intestines. Mineral oil is another emollient that has been used as a therapy for constipation and can be effective, but minimal absorption can occur with possible lipoid pneumonia so care should be exercised with use of this agent, especially in the extremes of age.

Normal transit constipation is generally treated with lifestyle modifications, bulking agents, and laxative therapies. There is limited data to suggest that lifestyle modifications such as increased fluid intake or exercise can treat constipation, but some of these recommendations can have beneficial effects on other aspects of patents' lives and should not be discounted as unhelpful.

Addition of bulking agents such as psyllium or calcium polycarbophil has been shown to increase the frequency and improve the consistency of bowel movements in patients with chronic constipation. Target doses should approach 10 grams of bulking agent per day and patients should be encouraged to increase their fluid intake.

Failing bulking agents, the next step for many clinicians is laxative therapy. There are several classes of laxatives from which to choose: osmotic laxatives, stimulant laxatives, or combination therapies. Osmotic laxatives consist of poorly or nonabsorbed ions, sugars, or molecules such as magnesium hydroxide, lactulose, or polyethylene glycol that create a hyperosmolar intraluminal environment. Stimulant laxatives are also called irritant laxatives and cause increased discharge of enteric neurons, resulting in increases in colonic serration and motility. Examples of stimulant laxatives include cascara, senna, aloe, castor oil, and diphenylmethane derivatives such as bisacodyl, sodium picosulfate, and phenolphthalein.

Secretagogues work by opening ion channels in the small and large intestines and include agents such as lubiprostone and linaclotide. Lubiprostone is the only currently available FDA-approved therapy for chronic idiopathic constipation and is prescribed at a dose of 24 mcg BID for this indication. Phase 3 trials of lubiprostone for chronic constipation demonstrated efficacy in both sexes regardless of age and showed that more than 60% of patients responded within 24 hours of the medication. These studies also showed that lubiprostone was associated with a relatively high incidence of mild nausea, which appears to be minimized when this medication is taken after a meal. Linaclotide is not FDA-approved for chronic constipation but phase 3 trials of this guanylate cyclase C agonist showed that it was an effective therapy for chronic constipation in a variety of doses versus placebo and was well tolerated.

Other agents such as colchicine, cholinergic agents, and neurotrophins have shown benefit as therapies for patients with chronic constipation. Additional studies of these therapies for this indication are needed.

Pelvic floor dysfunction

The most effective therapeutic approach to constipation that is due to pelvic floor dysfunction is biofeedback therapy or pelvic floor retraining. Studies have demonstrated that approximately 70% of patients will respond to this form of therapy within 5 to 6 sessions and that the response can be durable up to at least 24 months.

Repeat physiologic testing of patients who have responded to biofeedback or pelvic floor retraining has demonstrated normalization of abnormal defecatory patterns and contractions along with normalized pelvic floor coordination.

Slow transit constipation

Therapy for slow transit constipation can be challenging. Some patients can be managed with daily use of osmotic laxatives, but many will require combination therapies with laxatives from several different classes.

In pediatrics, antegrade lavage through a cecostomy has shown some promise for slow transit constipation.

In patients with acquired slow transit constipation from opiates, the newly approved mu opiate receptor antagonists such as methylnaltrexone have shown encouraging results.

In a small percentage of patients with true colonic inertia, colectomy may be required (see below). It is imperative that pelvic floor dysfunction and or secondary causes of constipation be excluded prior to undertaking surgical therapy for chronic constipation.

Surgery for chronic constipation

Surgery for severe constipation should be considered only after documented failure of medical therapy and exclusion of secondary causes of constipation. Three primary types of surgeries can be performed for severe chronic constipation: partial or total colectomy with continent anastamosis, stoma formation, or anorectal surgery (typically with a stapled transrectal resection) for documented pelvic floor dysfunction.

Studies evaluating long-term outcomes of colectomy for severe constipation have shown variable results in terms of patient satisfaction and complications. The most common complications of surgery for constipation include incontinence, diarrhea, and small bowel obstruction.

Preoperative evaluation should include upper and lower gastrointestinal transit studies, defecatory function studies, and psychological assessments. Studies that have evaluated outcomes in carefully selected patients with delayed colonic transit have shown high patient satisfaction scores, on the order of 90% or higher. The optimal surgical approach in these series appears to be a subtotal colectomy with ileorectal anastamosis.

What's the evidence?

Bharucha, AE, Wald, A, Enck, P. "Functional anorectal disorders". Gastroenterology. vol. 130. 2006. pp. 1510-18.

(Excellent description of the various anorectal disorders that can present with constipation as a primary symptom.)

Brandt, LJ, Prather, CM, Quigley, EM. "Systematic review of the management of chronic constipation in North America". Am J Gastroenterol. vol. 100(Suppl1). 2005. pp. S5-21.

(Series of systematic reviews and graded evidence recommendations for chronic constipation. Includes information on epidemiology, diagnosis, and treatment.)

Higgins, PD, Johanson, JF. "Epidemiology of constipation in North America: a systematic review". Am J Gastroenterol. vol. 99. 2004. pp. 750-9.

(Comprehensive evaluation and description of the typical patient profile associated with chronic constipation, highlighting key epidemiological differences and patterns among populations.)

McCrea, GL, Miaskowski, C, Stotts, NA. "A review of the literature on gender and age differences in the prevalence and characteristics of constipation in North America". J Pain Symptom Manage. vol. 37. 2009. pp. 737-45.

(Insightful overview of epidemiological patterns throughout the United States among patients with chronic constipation.)

Longstreth, GF, Thompson, WG, Chey, WD. "Functional bowel disorders". Gastroenterology. vol. 130. 2006. pp. 1480-91.

(Most recent update of the Rome committee report on chronic constipation and other functional gastrointestinal bowel disorders. Provides a framework for a positive diagnosis of chronic constipation and helps to highlight the differences between this condition and other functional bowel disorders such as IBS-C.)

Dipalma, JA, Cleveland, MV, McGowan, J. "A randomized, multicenter, placebo-controlled trial of polyethylene glycol laxative for chronic treatment of chronic constipation". Am J Gastroenterol. vol. 102. 2007. pp. 1436-41.

(Well done randomized controlled trial of PEG for chronic constipation. Although not FDA approved, this therapy is commonly used by clinicians and this study confirms that this can be an effective therapy for chronic constipation.)

Barish, CF, Drossman, D, Johanson, JF. "Efficacy and safety of lubiprostone in patients with chronic constipation". Dig Dis Sci. vol. 55. 2010. pp. 1090-7.

(Phase 3 data review of lubiprostone, the only FDA-approved therapy for chronic idiopathic constipation.)

Rao, SS. "Biofeedback therapy for constipation in adults". Best Pract Res Clin Gastroenterol. vol. 25. 2011. pp. 159-66.

(Excellent overview of the rationale, patient selection, evaluation, and treatment results with pelvic floor retraining for chronic constipation due to anorectal disorders.)

Locke, GR, Pemberton, JH, Phillips, SF. "AGA technical review on constipation: American Gastroenterological Association". Gastroenterology. vol. 119. 2000. pp. 1766-78.

(Comprehensive overview of the management of chronic constipation.)
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