Constipation is a common symptom, but it often remains unrecognized until the patient develops sequelae, such as anorectal disorders or diverticular disease. Several definitions of constipation have been proposed based on stool frequency in different populations. However, for surgical purposes, the most useful definition of constipation is a change in the bowel habit or defecatory behavior that results in acute or chronic symptoms or diseases that would be resolved with relief of the constipation.
Acute or subacute constipation in middle-aged or elderly patients should prompt a search for an obstructing colonic lesion. Acute constipation must be carefully distinguished from ileus secondary to intra-abdominal emergencies, including infections.
Although chronic constipation may be associated with psychological disturbances, the reverse is true as well. However, these issues are beyond the scope of this article.
The definition of constipation includes the following: infrequent bowel movements (typically <3 times per wk), difficulty during defecation (straining during more than 25% of bowel movements or a subjective sensation of hard stools), or the sensation of incomplete bowel evacuation.
Constipation is divided, with considerable overlap, into issues of stool consistency (hard, painful stools) and issues of defecatory behavior (infrequency, difficulty in evacuation, straining during defecation). Although hard stools frequently result in defecatory difficulties, soft bulky stools may also be associated with constipation, particularly in elderly patients with anatomic abnormalities and in patients with impaired colorectal motility.
Constipation is the end effect of several factors: poor diet, lack of exercise, motility abnormalities, and anatomic defects, along with the patient's expectations and psychological factors.
Constipation results in various degrees of subjective symptoms and is associated with abnormalities (eg, colonic diverticular disease, hemorrhoidal disease, anal fissures) that occur secondary to an increase in colonic luminal pressure and intravascular pressure in the hemorrhoidal venous cushions.
Nearly 50% of patients with diverticular or anorectal disease, when asked, deny experiencing constipation. However, nearly all of these patients have symptoms suggestive of defecatory straining or infrequency upon careful questioning.
Self-reported constipation is one of the most common GI disorders in the United States. About 2% of the population describe constant or frequent intermittent episodes of constipation.
Prevalence of self-reported constipation substantially varies because of differences among ethnic groups in how constipation is perceived.
A recent meta-analysis depicted prevalence rates as high as 81%, with a general incidence of approximately 17%. Female gender, age, and educational class were strongly associated with prevalence of constipation.1
Difficulty in defecation may cause substantial discomfort, abdominal cramping, and a general feeling of malaise.
- Actual or perceived constipation typically results in self-medicating with various laxatives. Although laxatives may correct the acute problem, the chronic use of them leads to habituation, requiring ever-increasing doses that result in drug dependency and, ultimately, a hypotonic laxative colon.
- Acute or chronic episodes of straining may cause acute or chronic hemorrhoidal disease (characterized by pain, itching, or bleeding) or acute hemorrhoidal thrombosis (characterized by intense pain and acute engorgement of 1 or more of the hemorrhoidal columns). Whether constipation actually causes hemorrhoidal disease is controversial. Upon careful questioning, these patients frequently provide a history of recent defecatory difficulties (with the exception of patients in the early postpartum period). Furthermore, conservative management of hemorrhoidal disease is more likely successful when future straining is prevented.
- The passage of hard stools may result in an acute anal fissure, which is a painful tear in the anoderm that may bleed. The regular passage of hard stools and the painful anal spasms during defecation that impinge the hard stools against the fresh wound prevent the anal fissure from healing. In addition to local wound care and analgesia, softening of stools is essential for successful management of an anal fissure.
- In the United States, both self-reported constipation and constipation requiring admission to a hospital are more frequent in black people than in white people.
- While constipation is less common in Asians, it is more frequent in those who adopt a Western diet.
- In contrast, constipation is less frequent among black Africans than white Africans, further suggesting that diet and other environmental factors play an important role.
In the United States, self-reported constipation and admissions to hospital for constipation are more common in women than in men. Surveys of apparently healthy young men and women demonstrate a slightly higher stool frequency among women.
See related CME at Impact of IBS With Constipation and Chronic Constipation on Women's Health: Current Concepts and Considerations.
- The prevalence of constipation increases exponentially in adults older than 65 years. This may reflect a combination of dietary alterations, decreases in muscle tone and exercise, and the use of medications, which may result in relative dehydration or colonic dysmotility.
- Some researchers have suggested that cumulative exposure to environmental neurotoxins may play a role in the age-related increase in the prevalence of constipation.
- In some patients, chronic or repeated pelvic injury (eg, from pregnancies) or the development of anatomic abnormalities (eg, rectal prolapse, rectocele [weakness in the posterior vaginal wall allowing the rectum to prolapse into the vagina upon straining]) may lead to functional outlet obstruction.
Basing the diagnosis of constipation on simply asking the patients whether they are constipated is associated with the marked underreporting of the problem in patients who have physical evidence of constipation, such as the presence of hemorrhoidal disease.
- History should begin with a detailed inquiry into the patient's normal pattern of defecation, the frequency with which the current problem differs from the normal pattern (eg, "missing a day"), the perceived hardness of the stools, whether the patient strains in order to defecate, and any other symptoms the patient may be experiencing.
- An inquiry concerning the amount of time spent on the toilet while waiting to defecate may also be illuminating. Patients should be asked to describe in detail what happens when they try to defecate and what maneuvers (pharmacological or physical) they have used to facilitate this process. These questions may suggest chronic laxative abuse or less common causes, such as colonic outlet obstruction.
- The duration of the problem is important. In adolescents or young adults, the duration of the problem may differentiate congenital defects from acquired causes. Neoplastic obstruction is less likely in patients older than 50 years who have had symptoms for at least 2 years.
- Questions regarding the onset of constipation may provide useful etiological information, either in terms of changes in diet, new medications, or associated psychosocial difficulties at that time.
- In addition to defining the nature of the patient's bowel habit, the factors that are likely to be responsible for the abnormal bowel habit should be delineated. Most patients who are constipated consume either too little fiber or too little water; therefore, assessing the patient's diet is useful. For acute changes in the bowel habit, a parallel dietary change should be ascertained. Learning how much fluid and what types of fluids the patient drinks on an average day is important.
- Epidemiological studies have clearly established a link between coffee consumption and worsening constipation.
- The diuretic effects of coffee, tea, and alcohol are likely counterproductive.
- Milk products may cause constipation in some individuals.
- The state of patients' bowel motility represents a balance between factors that promote motility and those that inhibit it.
- The most important influencing factor is exercise, which stimulates bowel motility. Conversely, the use of narcotics, antipsychotic agents, and other constipating medications reduce motility.
- Diuretics or substantial amounts of coffee, tea, or alcohol decrease available water to the colon.
- Chronic laxative abuse also causes refractory constipation.
- If the patient shows evidence of diseases or symptoms associated with constipation, such as diverticular disease, hemorrhoids, anal fissures, or fistula-in-ano, delineating these conditions historically and determining the nature of any previous treatment for these conditions is appropriate. For instance, patients with hemorrhoids may neglect to mention that they were previously treated for this problem or that they have been receiving medications for constipation for several years.
- Rectal bleeding should be taken seriously and evaluated carefully, particularly in patients older than 50 years or with a family history of colorectal disease.
- Patients with hemorrhoids may also have rectosigmoid cancer. Both cancer and hemorrhoids can produce bright red blood from the rectum.
- Most patients older than 50 years or with a family history of colorectal disease should be screened for colorectal cancer with at least a sigmoidoscopic examination.
- Finally, the evaluation should include the patient's description of the act of defecation.
- Pain during defecation might suggest a fissure or tenesmus from a rectal tumor.
- Painless inability to pass an otherwise soft stool suggests a rectal outlet obstruction.
- Neurological or endocrine disorders also can cause constipation.
- Most notably, diabetes may be associated with chronic dysmotility.
- Patients with hypothyroidism may exhibit decreased motility and slow transit times.
- Patients with panhypopituitarism, pheochromocytoma, or multiple endocrine neoplasia 2B are also at risk of developing constipation.
- When no other cause can be determined, a careful endocrine review is particularly important for patients with a recent onset of constipation and for patients who are refractory to conservative treatment.
- Similarly, central nervous system diseases, such as Parkinson disease, multiple sclerosis, stroke, CNS syphilis, and spinal injury or tumors, may cause constipation and should be considered in the patient's history and evaluation.
- Some cases of constipation may have a psychogenic component because constipation is a frequent somatic expression of psychological distress. Alternately, constipation may result in psychological disturbances.
- A history of sexual abuse is observed with unusual frequency in patients who are chronically constipated, particularly those with anismus.
- A history of other psychological abnormalities is often found, particularly among patients who are refractory to medical treatment and have normal bowel transit times and normal results from anorectal studies. Such factors should be gently explored in patients in whom the first-line conservative treatment has failed.
- Psychiatric referral may be appropriate in such patients after medical evaluation and therapy has been exhausted or if gentle questioning reveals some unexpected information.
In addition to the general evaluation, the abdomen, pelvis, and rectum, specifically, should be physically examined. Both the cause of constipation and its effects should be sought.
- Abdominal examination
- Abdominal distention or masses may indicate the presence of colonic stools or tumors.
- Large abdominal wall hernias, especially ventral hernias, may interfere with the generation of adequate intra-abdominal pressure that is required for the initiation of defecation.
- Rarely, a left-sided sliding inguinal hernia with an incarcerated sigmoid colon may cause difficulties in bowel movements.
- Conversely, the once-held belief was that elderly patients with new inguinal hernias should be assumed to have occult constipation due to partially obstructing colonic neoplasms and that those patients required colorectal cancer screening. The requirement for colorectal cancer screening in such patients remains controversial, and the pathophysiology underlying a link between colonic neoplasms and hernias is unknown because the lesions detected on screening are early lesions and are unlikely to have caused constipation.
- Pelvic examinations in women should specifically address the posterior vaginal wall, with attention to any evidence of internal prolapse or rectocele.
- This region should be palpated while the patient is at rest and then while she is straining to defecate.
- Many women with rectocele do not experience constipation. Good surgical results are not guaranteed, and a thorough preoperative workup to rule out other potential causes of constipation should always be performed.
- Perform a complete anorectal examination to determine the cause of constipation and to assess its effects.
- Causes of constipation that may be defined on rectal examination include the following:
- Anal fissure, particularly in children who retain their feces in order to avoid painful defecation
- Anal stenosis
- Partially obstructing rectal masses
- Rectal prolapse: The rectal prolapse may be either external or internal. The anus should be carefully examined for prolapse at rest and during a Valsalva maneuver. Care should be taken to distinguish a true full-thickness rectal prolapse from a mucosal prolapse, which is unlikely to cause constipation. Asking the patient to perform a Valsalva with the examining finger in the rectum in order to seek evidence of an internal prolapse may be worthwhile, although this is a relatively insensitive way to diagnose a prolapse. In contrast to inguinal hernias, rectal prolapses are typically related to constipation. At least 1 retrospective study has demonstrated a strong association between rectal prolapse and rectosigmoid neoplasms in patients older than 50 years. Sigmoidoscopy is probably indicated for these patients.
- In addition to delineating the cause of constipation, an anorectal examination should be used to determine the effects of the constipation.
- The presence of fissures or fistulae, evidence of scars from previous perirectal abscess drainages or other surgeries, and the nature of the patient's hemorrhoidal columns should be characterized.
- Enlarged hemorrhoids do not require treatment unless they cause symptoms.
- Although the effectiveness of fecal occult blood testing has been hotly debated, performing such a test following a rectal examination in patients older than 50 years is probably worthwhile.
- The presence of blood in the stool requires further evaluation.
- Never assume that the patient is bleeding from hemorrhoids or fissures until other sources of bleeding have been ruled out.
- A component of a complete physical evaluation of the patient should be to look for evidence of systemic diseases contributing to constipation. Such systemic diseases include the following:
- Endocrine dysfunctions, such as hypothyroidism, hypopituitarism, or diabetes mellitus
- Neurologic abnormalities, such as brain or spinal cord injury, peripheral neuropathy, multiple sclerosis, or Parkinson disease
Constipation may originate primarily from within the colon and rectum or may originate externally.
- Causes of constipation directly attributable to the colon or rectum
- Left colon obstruction (neoplasm, volvulus, stricture)
- Slow colonic motility, particularly in patients with a history of chronic laxative abuse
- Hirschsprung disease
- Chagas disease
- Outlet obstruction
- Outlet obstruction may be anatomical or functional. Characteristics of outlet obstruction include the following:
- Patients have difficulty evacuating bowels despite straining, often even with soft stools.
- Anatomic outlet obstruction may be due to intussusception of the anterior wall of the rectum on straining, rectal prolapse, and rectocele.
- Functional causes of outlet obstruction include puborectalis and/or external sphincter spasm when bearing down, short-segment Hirschsprung disease, and damage to the pudendal nerve, typically related to chronic straining or vaginal delivery.
- Causes of constipation outside the colon
- Poor dietary habit (most common)
- Systemic endocrine or neurologic diseases
- Psychological factors
- Dietary issues
- Inadequate water intake
- Inadequate fiber intake
- Overuse of coffee, tea, or alcohol
- Recent change in bowel habit paralleled with changes in the diet
- Medications that may contribute to constipation include the following:
- Iron supplements
- Nonmagnesium antacids
- Calcium-channel blockers
- Inadequate thyroid hormone supplementation
- Many psychotropic drugs
- Anticholinergic agents
- Although laxatives are frequently used to treat constipation, chronic laxative use becomes habituating and may lead to the development of a dilated atonic laxative colon, which requires increasing laxative use with decreasing efficacy.
- Systemic diseases
- Endocrine dysfunctions, most commonly hypothyroidism
- Neurologic dysfunction, including diabetic autonomic neuropathy, spinal cord injury, head injury, cerebrovascular accident, multiple sclerosis, and Parkinson disease
- Often, what appears to be acute or subacute constipation may represent a colonic ileus from systemic or intra-abdominal infection or other intra-abdominal emergencies.
Other Problems to Be Considered
- Laboratory evaluation does not play a large role in the initial assessment of the patient.
- Check thyroid-stimulating hormone levels to rule out hypothyroidism in patients refractory to dietary management.
- Determine serum electrolyte profile, including potassium, calcium, glucose, and creatinine, in patients with recent-onset constipation to assess an acute electrolyte imbalance and in chronically constipated patients for whom initial medical treatment has failed.
- Fecal occult blood should be tested in chronically constipated middle-aged or elderly adults to assess an obstructing neoplasm of the colon.
- Leukocyte count is useful for patients presenting with abdominal pain or fever or providing any indication that the constipation is secondary to an ileus. This may lead to further, more aggressive evaluation.
- Imaging studies are used to rule out acute processes that may be causing colonic ileus or to evaluate causes of chronic constipation.
- In patients with acute abdominal pain, fever, leukocytosis, or other symptoms suggesting possible systemic or intra-abdominal processes, imaging studies are used to rule out sources of sepsis or intra-abdominal problems.
- Order an upright chest roentgenogram and a flat and upright abdominal film. The abdominal film may reveal a colon full of stools, confirming the diagnosis of obstipation.
- Abdominal CT scan may be indicated to further evaluate the possibility of an intra-abdominal abscess.
- Acute constipation in the setting of an empty rectal vault and a proximal colon that is dilated with air or stool suggests large bowel obstruction, which should be further evaluated via Gastrografin enema or lower GI endoscopy.
- Gastrografin enema has the advantage of acting as an osmotic laxative, which may aid in the evacuation of the colonic contents.
- Air contrast barium enema is useful to assess the possibility of an obstructing colon cancer, intermittent volvulus, or colonic stricture in the setting of chronic constipation.
- A barium study is preferable to Gastrografin for patients who do not present with an acute process. On the other hand, Gastrografin is preferable for patients with an acute abdomen because this prevents the risk of extravasation of barium into the peritoneal cavity through a perforated diverticulum or colon cancer.
- In patients with suspected colonic obstruction, the author prefers to use colonoscopy instead of barium enema, but either may suffice.
- Defecography should be performed if an obstruction is suspected at the level of the anal canal.
- Fill the rectosigmoid with barium paste and fluoroscopically observe the act of defecation.
- This test may demonstrate alterations in the anorectal angle during defecation, presence of pelvic floor weakness, or transient rectal prolapse or intussusception.
- Controlled pressure-based rectal distension with fluoroscopic rectal imaging to measure the rectal diameter at the minimal distension pressure may be useful in identifying idiopathic megabowel in the absence of an organic cause of other problems.2
- Conversely, colonic transit time should be determined in patients suspected to have colonic motility disorder.
- Accomplish this by observing the passage of orally administered radiopaque markers via daily abdominal roentgenograms.
- Record the time taken for the passage of the markers and the site where they appear to be retained.
- A patient with outlet obstruction tends to retain the markers in the left colon and sigmoid, while a patient with colonic dysmotility may retain the markers throughout the colon.
- Lower GI endoscopy, anorectal manometry, electromyography, and balloon expulsion may be used in the evaluation of constipation.
- Lower GI endoscopy is useful in patients who are acutely constipated if large bowel obstruction is suspected based on an empty rectal vault and a distended proximal colon.
- Colonoscopy should not be performed if perforation or acute diverticulitis or other infectious processes are suspected because of the risk of worsening intra-abdominal contamination caused by colonic distension during the procedure.
- In the acute setting, bowel preparation is either not used or, at the most, 1-2 gentle enemas are used.
- Rigid endoscopy may be used in an urgent situation when flexible endoscopy is not available.
- Flexible endoscopy is generally preferred over rigid endoscopy because the former is more comfortable for the patient, provides a better view for the endoscopist, and permits access to more of the colon.
- Advance the flexible endoscope into the rectosigmoid until the site of the obstruction is reached or until the splenic flexure is identified, which suggests the absence of a rectosigmoid obstruction.
- If the initial sigmoidoscopy reveals no abnormal findings or if the constipation is more chronic, the patient should subsequently undergo a standard oral bowel preparation and either colonoscopy (the author's preference) or air contrast barium enema to more fully evaluate the remainder of the colon.
- Deep rectal biopsy, sometimes with double or triple bite techniques, may be used to diagnose Hirschsprung disease.
- Anorectal manometry documents several parameters. Interpreting the results of this test is complex and varies with the center performing the test. Consult a specialist familiar with the local testing facilities. These parameters include the following:
- External anal sphincter and puborectalis muscle function
- Reflex relaxation of the internal sphincter when the rectum is distended
- Coordination of these muscles during the bear-down phase of defecation
- Anorectal pressures during these events
- The threshold at which rectal distension is perceived
- This study documents paradoxical external sphincter or puborectalis spasm during defecation, consistent with the diagnosis of anismus.
- It is useful during subsequent biofeedback training because the patient is taught to relax these muscles.
- Balloon expulsion
- A balloon filled with varying amounts of water is rectally inserted. The patient is asked to expel the balloon.
- Decreased ability to expel a balloon filled with 150 mL of water suggests decreased defecatory ability.
- Manual disimpaction and transrectal enemas may be used after any critical illness associated with constipation has been ruled out.
Findings include the histology of any obstructing colonic lesion (eg, neoplasms, strictures from Crohn disease, diverticulitis, ischemia) and the agangliosis of Hirschsprung disease.
The key to treating most patients with constipation is correction of dietary deficiencies. These generally involve increasing fiber and fluid intake and decreasing the use of constipating agents, such as milk products, coffee, tea, and alcohol.
- Dietary fiber
- Dietary fiber is available in diverse natural sources, such as fruits, vegetables, and cereals. It is nutritionally superior to supplementation with purified fiber. However, advising patients to eat more fruits and vegetables is frequently unsuccessful, at least in American patients. Conversely, American patients respond reasonably well to prescriptions and often seek them. Prescribing a fiber supplement, such as wheat, psyllium, or methylcellulose, is often useful.
- Many of the available products vary substantially in their potency. For instance, sugar-free Metamucil has twice the potency of standard Metamucil on a volume basis because the latter is half sugar. Pharmaceutical companies may argue that one type of fiber is better tolerated or more effective than another. This may not make much difference in treatment or in fiber tolerance in most patients as long as the fiber supplementation doses start low and are slowly titrated upward. Theoretical considerations suggest that the use of a fermentable fiber, which increases short chain fatty acid concentrations in the colonic lumen, may have other health benefits (as opposed to methylcellulose). However, this remains controversial and awaits further exploration.
- Because no convincing reason exists to pick one product over another, a single brand of choice should be prescribed until the patient's constipation resolves. The patient may then switch to generic or other brands with appropriate dose adjustments. The author's experience has been that some patients have preferences based on the taste of the product or other subjective reasons. In particular, rare patients who cannot tolerate fermentable fiber supplementation because of resulting gas or bloating may do better with methylcellulose, while others find the quality of the stool, taste preferences, or both favoring psyllium supplementation.
- To avoid patient noncompliance due to the development of cramping and bloating that accompany changes in dietary fiber, fiber supplementation should be started at a low subtherapeutic dose and titrated upwards on a weekly basis until the desired effect is achieved. Patients should continue to increase the dose on a weekly basis until they experience daily bowel movements with no straining or until they achieve the maximum dose.
- Patients should be cautioned that these products are not laxatives, will not induce a bowel movement, and must be taken daily regardless of their perceived need.
- Patients may increase or decrease their dose on a week-to-week basis. In particular, the author advises patients who have arrived at what they believe to be an appropriate and successful dose to increase the dose one additional step for at least a week and then back down if they wish. Some patients actually prefer the higher dose. To ensure long-term compliance, the author believes that patients should titrate the doses in case of changes in potency between fiber supplement brands or changes in diet, fluid intake, or exercise.
- Patients should be cautioned that, although various stool softeners, such as docusate sodium, appear much more palatable than fiber, they are not suitable for long-term use. Tachyphylaxis to stool softeners develops over time.
- Fluid intake
- Fluid intake is the key to treatment. Patients should be advised to drink at least 8 glasses of water daily. Counseling may be required to achieve this goal.
- Milk and milk products should be minimized if these prove constipating.
- In some patient populations, most consumed fluids consist of coffee, tea, and alcohol. Patients should understand that this practice is counterproductive because of the diuretic effects of these products. The author usually recommends that patients decrease consumption of coffee, tea, and alcohol as much as possible, and they should consume an extra glass of water for every drink of coffee, tea, or alcohol.
- Failure to control constipation on a regimen of fiber supplementation and water should prompt the analysis of patient compliance and the search for other physical causes, such as altered colonic transit time, outlet obstruction, and psychological causes. The author's experience is that early failures usually reflect inadequate water intake, while recidivism months to years later usually corresponds to a patient having decided that the fiber supplementation is no longer necessary. Counsel patients in advance to avoid these inappropriate decisions.
- In selected patients who comply with but do not successfully treat their constipation with a trial of a high fiber, high water diet, a trial of a very low residue or even a liquid diet may be appropriate.
- Such a regimen is most successful in patients with outlet obstruction who are not candidates for surgical correction and in patients whose presentation is more characteristic of irritable bowel syndrome with a chief complaint of abdominal pain.
- A low residue diet may be effective in the latter group of patients if thorough mechanical cleansing of the bowel, such as is done for diagnostic endoscopy or barium enema, temporarily relieves their symptoms.
Although some controversy exists about the effectiveness of exercise in constipation treatment, encouraging as much aerobic exercise as possible seems reasonable. Even brisk walking may help stimulate bowel motility and, certainly, is unlikely to hurt most patients.