AGA technical review on constipation☆

Article Outline

• Abstract
• Epidemiology of constipation
• Risk factors for constipation
• Economic impact
• Clinical features and pathophysiology
• Clinical evaluation
• Secondary encounters and referral consultations
• Diagnostic tests
  • Balloon expulsion test
  • Defecography
  • Colonic transit
  • Anorectal manometry
• Medical management
• Role of surgery
  • Surgical treatment of STC
  • Surgical treatment of defecation abnormalities
  • Descending perineum syndrome
  • Stoma
• Conclusions
• Acknowledgements
• References
• Copyright

Abstract 

This literature review and the recommendations therein were prepared for the American Gastroenterological Association Clinical Practice and Practice Economics Committee. The paper was approved by the Committee on March 4, 2000, and by the AGA Governing Board on May 21, 2000.

GASTROENTEROLOGY 2000;119:1766-1778

Abbreviations:  IBS , irritable bowel syndrome, STC , slow-transit constipation

The symptom of constipation is very common.¹, ² The aisles of any drugstore confirm the impact of this problem. The goal of this technical review is to identify a rational, efficacious, and ideally cost-effective approach to the patient presenting with constipation. The perspective will be that of the practicing gastroenterologist. Constipation in children will not be specifically addressed, nor will special populations such as patients with spinal cord injury.

The background for this technical review, especially the subthemes comprising the clinical syndromes, their epidemiology, diagnosis, treatment, and their socioeconomic impacts have been subjects of recent reviews and monographs.¹, ³, ⁴ These were supplemented by selected and focused literature searches. Our discussion of the epidemiology of constipation is based on peer-reviewed, published surveys. Estimates of the economic impact to society have been published; however, formal cost-effectiveness analyses for specific diagnostic and therapeutic algorithms have not been performed. Comparisons of diagnostic approaches, with precise estimates of specificity and sensitivities, also have not been published. Indeed, in many instances, individual diagnostic techniques have not been even standardized. Moreover, most reports of treatment have not separated clearly patients with slow-transit constipation (STC) from those with disorders of the pelvic floor. There are few well-designed clinical trials of therapy, and only one meta-analysis of comparable studies has been published. Most evidence must, therefore, be based on clinical experience, descriptive studies, and reports of expert committees. Where possible, we indicate those studies that have tested for transit defects and pelvic floor dysfunctions.

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Epidemiology of constipation 

Before addressing the question “how common is constipation?,” one must first define it, although even this fundamental issue is answerable only imperfectly. The typical medical definition of constipation emphasizes infrequent or difficult evacuation of feces,⁵ and physicians often define constipation as a bowel movement every 3 to 4 days or less.⁶ This opinion is likely based on a study of otherwise healthy people in Great Britain that found that 99% of the population had between 3 bowel movements a week and 3 bowel movements a day.⁷ However, patients often have different opinions. In a survey of young adults not seeking medical care, Sandler and Drossman⁸ found that 52% defined constipation as straining to pass fecal material, 44% felt it was the process of passing hard stools, only 32% thought it merely to be the infrequent passage of stools, and 34% thought the term referred to an inability to defecate at will. Thus, it must be recognized that self-reported constipation is just as likely to refer to straining or hard stools as it is to focus on infrequent stooling.

In an effort to introduce uniform standards to clinical research, an international panel of experts developed a consensus definition of constipation.⁹, ¹⁰ Several components were included, consisting of straining, hard stools, feelings of incomplete evacuation, or 2 or fewer bowel movements per week. Debate continues as to whether patients with 2 or fewer bowel movements per week should be considered to have constipation irrespective of their response to the first 3 questions. These criteria, initially published in 1992, were recently revised (Table 1).¹¹

Table 1. Definitions of constipation

Criteria from Thompson et al.¹¹

Recognizing that differences in the definition of constipation preclude firm conclusions, how common is it? Sonnenberg and Koch¹² reviewed the data from several nationwide surveys and estimated the prevalence at 2% of the U.S. population (approximately 4 million people). In this analysis, constipation was the most commonly reported digestive complaint. A similar result (3%) was obtained in the U.S. householder study of Drossman et al.² Everhart et al.¹³ used a different set of federal data and reported a much higher prevalence rate: 21% in women and 8% in men. Stewart et al.¹⁴ surveyed more than 10,000 subjects and estimated a prevalence of 28%, which when extrapolated to the U.S. population equals 55 million people. Other surveys have arrived at estimates varying throughout this range, 2%–28%.¹, ¹⁵, ¹⁶, ¹⁷

What can we conclude? Constipation is common; any disorder that affects >1% of the population can surely be so designated. Exactly how common depends greatly on the definition used. Finally, it should be emphasized that all published studies have addressed only the prevalence of constipation (the proportion of the population with constipation at any point in time); data on incidence, i.e., the rate of development of new symptoms of constipation, are lacking.

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Risk factors for constipation 

Although absolute prevalence estimated from these studies differs widely, there is good agreement as to the risk factors for constipation.¹², ¹³, ¹⁸, ¹⁹, ²⁰, ²¹, ²² Most studies find that self-reported constipation is more common in women than in men and that the prevalence increases with age. In one study, although self-reported constipation and laxative use increased with age, the proportion of subjects with 2 or fewer bowel movements per week was not associated with age.²³ Constipation is associated with inactivity, low calorie intake, the number of medications being taken (which is actually independent of the profiles of their side effects), low income, and a low education level.¹², ¹³, ¹⁸, ¹⁹, ²⁰, ²¹, ²² Constipation has not been reported to be associated with a low intake of fiber in any study to date. However, interpretation of this point is not simple, because these data come from cross sectional studies and thus do not take into account the number of persons who increased their fiber intake as treatment for constipation. Constipation is associated with depression as well as physical and sexual abuse.²⁴ Each of these increases the risk of constipation. However, one should not assume these are causative, nor should one assume that treatments directed toward the modification of risk factors will result in improved bowel function. For example, although inactivity is associated with constipation, exercise has not clearly been shown to be an effective treatment. Clinicians may try to modify these risk factors, but need to recognize that data from clinical trials are lacking.

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Economic impact 

Given the number of people who in questionnaires report constipation, it comes as no surprise that this symptom contributes significantly to the costs of health care. Sonnenberg and Koch²⁵ estimated that the condition accounted for 2.5 million physician visits per year; indeed, 1.2% of the U.S. population presented to a physician with constipation in any one year. Consultation was more common among women and increased with age. This rate of visits was stable from 1958 to 1986. Of these patients, 31% were evaluated by general or family practitioners, 20% were seen by general internists, and only 4% were referred to gastroenterologists. Nevertheless, this equals 100,000 patients referred to gastroenterologists for constipation per year. To place the 2.5 million physician visits into perspective, 150,000 people develop colon cancer and 25,000 people develop pancreatic cancer in the United States each year.²⁶ These relative numbers highlight the problems of effectively identifying patients with colon cancer from among the multitude of patients with constipation. Moreover, they point out the potential benefits to society of a clearer approach to this symptom, such as when it does or does not warrant more extensive investigation.

Almost all (85%) physician visits for constipation result in a prescription for laxatives or cathartics.²⁵ Population-based data are lacking as to the number of tests and procedures performed for constipation in the United States. In a study of 51 patients seen in a surgical referral clinic (tertiary care), the average cost of the diagnostic evaluation was $2752.²⁷ The largest line item was the colonoscopy, which was responsible for more than one third of the total expenditures. These investigators calculated the cost per patient who benefited by the evaluation to be $11,697.²⁷ Certainly, society cannot afford to pay for 2.5 million people to undergo such an evaluation, because this would cost $6.9 billion, plus the costs of any treatment. To put this figure in perspective, the Medicare program has budgeted $500 million per year for the new screening program for colorectal cancer!

Economic analyses have suggested that screening for colon cancer is cost-effective.²⁸ Formal economic analyses of the evaluation of constipation have not been performed. Because it is unlikely that patients with constipation are at lower risk for cancer, the performance of an anatomic evaluation of the colon in constipated patients is thus likely to also be cost-effective. Constipation may, in fact, indicate a higher risk of colorectal malignancy²⁸, ²⁹; thus, exclusion of malignancy perhaps is the most cost-effective first step in approaching a patient with constipation.

To summarize these general aspects, constipation is common in the community, with prevalence estimates as high as 28%. A minority of those with constipation seek medical care, but this still accounts for 2.5 million annual visits in the United States. Most people see primary care providers and receive a prescription for laxatives. They may undergo an anatomic evaluation of the colon. The role of the gastroenterologist is to assist in identifying selected patients with constipation who might benefit from additional testing or more specific treatments. By doing this, scarce health care resources may be used most efficiently.

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Clinical features and pathophysiology 

Although physicians often focus mainly on the infrequency of bowel movements in the definition of constipation, patients have a broader set of complaints. The lower limit of normal stool frequency usually quoted is 3 per week,⁷ and 2 or fewer stools weekly was included as one of the Rome criteria (Table 1). In this definition, frequency was only 1 of 6 prime features (including straining, hard stools, and a feeling of incomplete evacuation). It has been estimated that the symptoms encompassed by the patients' definitions are (in decreasing importance) straining, stools that are excessively hard, unproductive urges, infrequency, and a feeling of incomplete evacuation.³⁰ An adequate evaluation of the symptom must, therefore, include an informed and directed history of the specific features. What is it that constitutes “constipation,” in the view of this patient? The interview must also elicit a complete list of prescription and over-the-counter drugs. Constipating side effects are widespread among common medications (Table 2); moreover, most patients who feel they are constipated will be trying to relieve symptoms, often with self-prescribed over-the-counter agents. Thus, the pattern of laxative use, and sometimes abuse, must be established if the sequence of alternating constipation and diarrhea, so common in irritable bowel syndrome (IBS),¹⁰, ¹⁵, ¹⁶, ¹⁷ is to be recognized. In population studies, laxative use and abuse are present in 7% and 4%, respectively.³¹, ³²

Table 2. Medications associated with constipation

In addition to the usual definitions of constipation, Table 1 includes the symptoms of “evacuatory failure,” and herein is a significant conceptual advance in the understanding of constipation.⁴, ³³, ³⁴, ³⁵, ³⁶ Two major pathophysiologies can now be identified, with a third being the coexistence of both in the same patient. STC (“colonic inertia”) is thought to have as a primary defect slower than normal movement of contents from the proximal to the distal colon and rectum.⁴, ³⁶, ³⁷, ³⁸, ³⁹ In some individuals, the basis for slow transit may be dietary or even cultural.⁴⁰, ⁴¹, ⁴², ⁴³ In others, slow colonic transit probably has a true pathophysiologic basis in abnormal colonic motility. It has been suggested that there are 2 subtypes of STC⁴⁴: (1) colonic inertia, possibly related to decreased numbers⁴⁵, ⁴⁶ of high-amplitude propagated contractions. These peristaltic sequences are thought to be the mechanism for the mass movement of contents, and their absence is expressed as prolonged residence times of fecal residues in the right colon,³⁹ and (2) increased, uncoordinated motor activity in the distal colon that offers a functional barrier or resistance to normal transit.⁴⁴ This distinction requires colonic manometry for its definition, these techniques are not generally available, and are not appropriate for the bulk of patients, except in research settings.

The other major pathophysiology, pelvic floor dysfunction, features normal or slightly slowed colonic transit overall but a preferential storage of residue for prolonged periods in the rectum.⁴, ³³, ³⁴, ³⁵, ³⁶ In this instance, the primary failure is one of an inability to evacuate adequately contents from the rectum. This functional defect has received numerous names (“outlet obstruction,” “obstructed defecation,” “dyschezia,” “anismus,” “pelvic floor dyssynergia”); this plethora of pseudonyms for a heterogenous syndrome has complicated, and perhaps confused, what otherwise is an important conceptual step. Less well understood at this time are the putative pathophysiologies that lead to this end point, i.e., the inability to empty stools from the rectum. The simplest possible classification would subdivide evacuatory failure into the following: (1) examples of muscular hypertonicity (failure to relax or “anismus”); incomplete relaxation³⁵ or paradoxical contraction of the pelvic floor and external anal sphincters during attempted defecation does occur, although this phenomenon may be less frequent than originally proposed⁴⁷, ⁴⁸, ⁴⁹; and (2) muscular hypotonicity, sometimes with megarectum and excessive pelvic floor descent.⁵⁰, ⁵¹ These syndromes are multifactorial,⁴⁹ and some are not yet well understood. The role of excessive straining, leading to or associated with excessive perineal descent, obstetrical damage to the perineal nerve, constipation, rectal intussusception, solitary rectal ulcer syndrome, and fecal incontinence is not entirely clear.⁴, ⁴⁸, ⁴⁹, ⁵⁰, ⁵¹, ⁵², ⁵³, ⁵⁴

When evaluated carefully, a proportion of patients seen at tertiary referral centers have some features of both sets of disorders.³⁶, ⁵⁵, ⁵⁶ Indeed, separation of STC from disorders of evacuation as the major cause of constipation is extremely important because the primary therapeutic approaches differ significantly. Surgical series have pointed out clearly that evacuatory failure needs to be sought and, if present, treated before any decision is made about surgical therapy for intractable constipation.³⁶, ⁵⁵, ⁵⁶

Insight into the pathogenic mechanisms of intractable constipation can be gained from referral series.²⁷, ³⁶, ⁵⁵, ⁵⁶, ⁵⁷ In the largest series,³⁶ of 1000 patients referred to a tertiary center for the medical and surgical evaluation of intractable constipation, 59% had normal colonic transit (or slightly delayed only). These were likely examples of IBS with constipation; 28% had pelvic floor dysfunction (with or without slow transit), and 13% had slow transit only. An earlier examination of a similar cohort draws attention to the point that patients with significant complaints of abdominal pain were more likely to have normal or slightly delayed colonic transit, and perhaps to be more representative of IBS.⁵⁸ On the other hand, chronic constipation may represent an, as yet, unrecognized expression of a neuropathy of the colon's enteric nervous system.⁵⁹

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Clinical evaluation 

Historical features are key, and the questioning must be specific. What feature does the patient rate as most distressing? Is it infrequency per se, straining, hard stools, unsatisfied defecation, or symptoms that occur between infrequent bowel movements (bloating, pain, malaise)? Strong emphasis on these last characteristics suggests an underlying IBS.¹⁰, ⁵⁷

Pelvic floor dysfunction should be suspected strongly on the basis of a careful history and physical examination. Prolonged and excessive straining before elimination are suggestive; when evacuatory defects are pronounced, soft stools and even enema fluid may be difficult to pass. The need for perineal or vaginal pressure to allow stools to be passed or direct digital evacuation of stools are even stronger clues. It is important to raise this question early, because evacuatory disorders do not respond well to standard laxative programs, and failure to recognize such a component is a frequent reason for therapeutic failure. However, although evacuatory disorders may be over-represented in referral series, they are also common in population surveys.³¹

The current regime and bowel pattern should be recorded. How often is a “call to stool” noted? Is the call always answered? What laxatives are being used, how often, and at what dosage? Are suppositories or enemas used in addition? How often are the bowels moved, and what is the nature of the stools? Physicians and patients need to be aware that, after a complete purge, it will take several days for residue to accumulate such that a normal fecal mass will be formed. Many commonly used medications have constipation as a notable side effect (anticholinergics, calcium channel blockers; see Table 2). A full record of prescription and over-the-counter medications must be obtained.

The physical examination and screening tests, if deemed appropriate, should also eliminate diseases to which constipation is secondary (Table 3). Physical findings of more direct importance are confined to the perineal/rectal examination, but these may be key:

Table 3. Common medical conditions associated with constipation

At the conclusion of the initial clinical evaluation, it should be possible to classify tentatively the patient complaining of constipation into one (or possibly more) of the following categories:

The degree to which some or all of the possibilities listed in Table 3 need to be sought will vary greatly. Most patients will require structural studies (flexible sigmoidoscopy plus barium enema or colonoscopy) and blood chemistries to exclude metabolic disorders. In some instances, treatment will be available for the primary disorder (hypothyroidism, hypercalcemia, rectal stricture, etc.). When not available or inadequate (e.g., scleroderma, amyloid, neurologic disease), the challenge of adequate symptomatic treatment remains (see later). In most instances at the level of the primary consultation, it will be sufficient to exclude organic and secondary constipation on clinical grounds, supplemented by selected diagnostic studies, and to treat symptomatically.

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Secondary encounters and referral consultations 

Patients are referred for specialty consultation usually because their complaints continue despite the use of fiber supplementation and simple laxatives, and after conditions to which constipation may be secondary have been evaluated. The gastroenterologist will then need to consider the following major issues:

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Diagnostic tests 

These can be summarized most simply as an algorithm (Algorithm 1; see preceding Medical Position Statement). The sensitivities of these investigations has not been established; indeed, the details of their performances have not been well specified. Although there is general agreement as to the preferred approach,⁵⁰, ⁵¹, ⁵⁵, ⁵⁶, ⁶⁰, ⁶¹, ⁶², ⁶³ our recommendations represent, at this time, the views of the authors. The issue of the best diagnostic approach is compounded further, because interpretation of any single test must be guarded. It should be recognized that patient cooperation is a key voluntary component of most tests of anorectal function (e.g., expulsionary efforts, squeeze pressures). Patients may be restricted by feelings of inadequate privacy, and these voluntary components will, of necessity, vary among patients, and even for the same person at different times. Thus, the tests should be in a setting as private as possible, to reduce embarrassment and facilitate cooperation, but ideal conditions are rarely possible. We list in order of simplicity, cost, and general use, the studies referred to in the algorithm. However, none of these has been subjected to strict evaluation of specificity and sensitivity.

Balloon expulsion test 

This simple procedure, first described by Preston and Lennard-Jones,³⁵ quantifies the ability of a patient to evacuate a water-filled (usually 50 mL) balloon. It can be performed easily in conjunction with anorectal manometry and can be quantified by noting the magnitude of additional passive forces needed to expel the balloon if spontaneous evacuation is not possible.⁶⁰ Although never evaluated systematically, it is a simple, useful screening test for major dysfunctions of evacuation, and can also serve as a functional marker for biofeedback programs of pelvic floor retraining.

Defecography 

Defecatory function can be measured either scintigraphically or radiographically. The scintigraphic method evaluates anorectal angulation and pelvic floor descent during evacuation, and can also quantify the evacuation of artificial stools.⁶⁰ Its advantage is simplicity and minimal radiation exposure; the disadvantage is that anatomic defects may not be as well seen as with barium defecography.⁵⁰, ⁶¹ Barium defecography can be performed in conjunction with a standard barium enema (for structural evaluation of the whole colon), and thus an anatomic/functional evaluation of defecation can be performed at the same time. Of the observations possible with these techniques, the most relevant are (1) the failure of the anorectal angle to open (i.e., become more obtuse) during defecation and (2) the degree of pelvic floor descent during defecation. Decreased descent is a component of impaired pelvic floor relaxation (“anismus”), and, conversely, excessive descent (“descending perineum syndrome”) can also be a pathophysiologic mechanism of constipation. In this instance, excessive straining, internal intussusception, solitary rectal ulcers, and prolapse may also occur.⁵¹, ⁵², ⁵³, ⁵⁴

Colonic transit 

Rates at which fecal residue moves through the colon are important determinants of fecal form, which can be categorized from liquid, to semiformed, to pellety stools.⁶³, ⁶⁴ The method most commonly used to measure transit is that of radiopaque markers, first introduced by Hinton et al.⁶⁵ and subsequently refined and simplified.⁶⁶ These are inexpensive tests that are possible at any medical center (markers are available from Sitz-Mark, Konsyl Pharmaceuticals, Fort Worth, TX). The test is reproducible⁶⁷ and can be recommended for any patient in whom constipation is a major symptom.

Less widely used are radionuclide gamma scintigraphic techniques.⁶⁴, ⁶⁷ Radiographic and scintigraphic methods correlate well,⁶⁴, ⁶⁷ with the major advantage of scintigraphy being that only 24 or 48 hours of scanning are needed, whereas the radiopaque techniques require 5–7 days for completion.⁶⁶ Whitehead's laboratory⁶⁸ lengthened the radiopaque marker test to 5 days and reported a more precise evaluation of severely constipated patients. This may be the preferred approach. It should be remembered that rectal distention by retained stools can slow colonic transit,⁶⁹ and severely constipated patients should have laxatives and/or enemas to empty the colon before a study of transit.⁷⁰

Anorectal manometry 

The subject has been reviewed extensively by Diamant and colleagues in a technical review and medical position statement for this series of Practice Guidelines.⁶², ⁶³ Precise methodologies vary between laboratories, and local normal values need to be developed and recognized. Until a standardized methodology can be accepted, data from center to center cannot be generalized. The procedure has greatest value in (1) excluding Hirschsprung's disease by the presence of a normal rectoanal inhibitory reflex and (2) providing supportive data for clinical or physiologic suggestions of pelvic floor dysfunction. For example, high basal sphincter pressures with relatively little voluntary augmentation,⁵⁶ suggest spastic pelvic floor/sphincter dysfunction (anismus).

This review will not consider tests that are used in clinical research or that are generally not applicable to practice. These include (1) specific tests of rectal perception of distention or electrical stimuli, (2) electromyography of the external sphincter or puborectalis, and (3) pudendal nerve terminal motor latency. We agree with Diamant et al.⁶² that these studies, although of value in highly selected instances, or for research purposes, are not part of the standard armamentarium. These investigators also point out the potential role of surface electromyograms in the therapeutic mode of biofeedback. Additional details can be found in specific reviews.⁴, ⁶², ⁷¹

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Medical management 

Treatment algorithms as included in the Medical Position Statement encapsulate our suggestions, and Table 4 is an extensive listing of common laxative agents including dosages and costs.

Table 4. Summary of medications commonly used for constipation

GI, gastrointestinal; tsp, teaspoon; tid, three times daily; qd, every day; bid, twice a day; SCFAs, short-chain fatty acids; CCK, cholecystokinin; PEG, polyethylene glycol.

As a beginning approach, we suggest a gradual increase in fiber intake. This can be incorporated into the diet (Table 5) or used as standardized fiber supplements (Table 4).

Table 5. Content of dietary fiber of common foods

NOTE. One serving equals ½ cup unless noted.

Patients need to be instructed as to how to best use fiber supplements. They should not expect an immediate response (as can be expected with a purgative), but should embark upon a program of several weeks' duration, decreasing or increasing the daily dose of fiber after a 7–10-day period. They should begin with 2 daily doses (AM and PM), with fluids and/or meals. They should be warned that fiber supplements usually increase gaseousness, but that the symptoms often decrease after several days.

If more treatment is needed, the next simplest program should begin with an inexpensive saline agent, such as milk of magnesia. Patients can often titrate the dose such that soft, but not liquid stools, are achieved. Only later should stimulant agents (Dulcolax) or more expensive agents such as lactulose and polyethylene glycol (PEG) be considered. In general, simple or STC should be able to be controlled by one or other of these regimes. The saline laxatives all have the same mechanism of action, osmotic retention of fluid in the gut lumen, and the choice of agent (magnesium hydroxide, magnesium sulfate, sodium phosphate, sodium sulfate, etc.) is largely arbitrary. Variations on the saline/osmotic theme with PEG-electrolyte solutions (e.g., Golytely) have no conceptual advantage, and nonabsorbable carbohydrates (lactulose, sorbitol) are often limited by their extreme potential to produce gas, by bacterial metabolism of unabsorbed carbohydrate.

In the only meta-analysis of therapeutic trials, Tramonte et al.⁷² excluded 85% of 733 reports (not controlled), 11% for other reasons, and were able to evaluate 25 different treatments in 36 randomized trials. They concluded, “Both fiber and laxatives modestly improved bowel movement frequency in adults with chronic constipation. There was inadequate evidence to establish whether fiber was superior to laxatives or one laxative class was superior to another.”⁷²

Stimulant laxatives (senna, bisacodyl) have traditionally been discouraged based on the silver staining results of Barbara Smith,⁷³, ⁷⁴ which suggested that their long-term use damaged the enteric nervous system, perhaps irreversibly. However, the silver staining method is technically quite tricky, and subsequent observations using electron microscopy and immunohistochemistry have not confirmed her conclusions.⁷⁵, ⁷⁶ Neurologic damage might just as readily be the cause, not the result,⁵⁹ and reticence to condone long-term stimulants is now much less.

Cisapride is a benzodiazepine that was developed as a prokinetic directed primarily to the upper gut. It has been used extensively for the treatment of constipation also; the results are quite equivocal.⁷⁷, ⁷⁸, ⁷⁹, ⁸⁰ Concerns over its safety caused it to be withdrawn from the market in July 2000. Other prokinetics are being developed with more selective actions on the colon, and novel agents are under study as colonic prokinetics.⁸⁰, ⁸¹ Attention has also been directed toward the use of additional pharmacologic approaches with prostaglandins⁸² because diarrhea is a common side effect of their use for other purposes. This is expensive and perhaps illogical, because it is using the side effect of a potent drug to treat constipation. Another example, colchicine,⁸³ may be even less defensible. Although inexpensive, it is a cytotoxin that has long been used to treat gout, with a known propensity to produce diarrhea. In patients with a chronic problem such as constipation, the danger of major neuromuscular complications needs to be appreciated, especially if renal function is impaired.⁸⁴

However, before these therapeutic regimens should be initiated, major decisions need to be made relating to the contribution of pelvic floor dysfunction. It must be recognized that disordered evacuation will respond poorly to more and more oral laxatives.⁸⁵ Thus, the question must be asked, is the role of impaired evacuation sufficient to justify an intensive program of pelvic floor retraining and biofeedback? Formal evaluations of biofeedback training in constipation are sparse, and important practical details of individual programs are often not stated. The subject has been reviewed recently in this series.⁶² However, the motivation of the patient and therapist, together with the frequency and intensity of the retraining program, likely contribute importantly to the chances of success. In addition to biofeedback therapists, dietitians and behavioral psychologists should participate. The results of biofeedback in children have been disappointing,⁸⁶ but intensive programs in adults can have a 75% success rate or better.⁸⁷, ⁸⁸, ⁸⁹, ⁹⁰

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Role of surgery 

Surgical treatment of STC 

The treatment of colonic inertia, when well documented and assuming failure of an aggressive and prolonged trial of laxatives, fiber, and prokinetics, is total colectomy with ileorectal anastomosis.³⁶, ⁵⁵, ⁵⁶ Patients need to be told that the procedure is designed to treat the symptom of constipation (difficult and infrequent evacuation) and that other symptoms (e.g., abdominal pain and bloating) that the patient associates with constipation may not necessarily be relieved by achieving regular defecation. Colectomy is performed to the level of the sacral promontory with an anastomosis between the terminal ileum and upper rectum. The presacral space is entered with careful preservation of the sympathetic nerves.³⁶, ⁵⁵

Ileorectostomy is more successful than ileosigmoidostomy.⁹¹ If any part of the sigmoid colon is left in place, constipation may recur, whereas an anastomosis at a level below 7–10 cm from the anal verge may result in an unacceptably high frequency of bowel movements and sometimes fecal incontinence. As with segmental resection or partial colectomy, removal of the colon with preservation of the cecum and ileocecal valve has been shown to be associated with poor results.⁹² If the cecal reservoir is maintained, dilatation follows and constipation recurs. In patients in whom a thorough physiologic evaluation has been undertaken, with demonstration of convincing evidence of colonic inertia and no evidence of outlet obstruction, prompt and sustained relief of constipation can be expected.⁵⁵, ⁵⁶ Patients who continue to be constipated after ileorectostomy are likely to have abnormal pelvic floor function.⁵⁵, ⁵⁶

Surgical treatment of defecation abnormalities 

It seems plausible that division of the posterior fibers of the puborectalis muscle may be beneficial in patients in whom the muscle contracts paradoxically at the time of defecation. However, this appears not to be so.⁹³, ⁹⁴ Partial division of the puborectalis either in the posterior plane or laterally has been disappointing. Dividing the inner fibers of puborectalis on either side of the midline produced symptomatic improvement in only 1 of 7 patients, whereas lateral division of the muscle produced improvement in only 3 of 15.

Descending perineum syndrome 

Constipation also occurs in patients with “descending perineum syndrome.”⁹² Such patients strain endlessly at stool but the rectum empties incompletely. The perineum is seen to bulge well below the plane of the ischial tuberosities. This abnormal perineal descent is probably secondary to injury to the sacral nerves from either childbirth or chronic straining at stool.⁵¹, ⁵² Incomplete evacuation leads to more straining, more traction on the nerves, and progressive denervation of the external anal sphincter and puborectalis. In time, this scenario leads to fecal incontinence and thereby compounds the patient's misery. Surgery cannot correct this problem, which is best treated with biofeedback, although success is only about 50%.

Stoma 

Patients sometimes request a stoma because of constipation. A stoma may be a good option, as it can be reversed. Again, careful selection of patients is essential. A colostomy allows the possibility of colonic irrigation, but a number of authors have reported unsatisfactory results because of persisting colonic inertia proximal to the site of the ostomy or a more generalized disorder of motility.

A recently described operation called a “continent colonic conduit” may be an answer for some patients.⁹⁵ The sigmoid colon can be used as a continent conduit by transection at its midpoint; then, by fashioning creation of a 3-cm longitudinal incision in the anterior wall of the distal colon 15 cm from the divided end, and by intussuscepting a 5-cm segment of colon commencing 5 cm from the transected end, a valve is created. The valve serves to prevent reflux of fecal material. The conduit is brought out onto the anterior abdominal wall, and intestinal continuity is re-established by anastomosing the proximal sigmoid colon to the upper rectum. Patients are taught to intubate and irrigate the conduit. The procedure is successful in reducing the time the patient spends evacuating rectal contents and increases the number of bowel movements. The procedure is also reversible but complex.

Thus, of the many patients complaining of constipation, only a small fraction³⁶ will benefit from surgical treatment, probably 5% of highly selected, referred population, and a minuscule proportion of the total cohort.

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Conclusions 

Based on the preceding review, an algorithmic approach to patients with constipation can be devised (see Algorithms 1–3 in the preceding Medical Position Statement).

After the initial history and physical examination, it should be provisionally possible to classify patients into one of several subgroups. Standard blood tests (complete blood count, thyroid-stimulating hormone, calcium) and a colonic structural evaluation (flexible sigmoidoscopy and barium enema or colonoscopy) should be performed to rule out organic causes of the constipation. Patients with known neurologic conditions need these to be addressed. If the initial evaluation is normal or negative, an empiric trial of fiber (and/or dietary changes) can be followed by simple osmotic laxatives. Most patients will obtain symptom relief with these measures.⁴

Patients who fail to respond to this initial approach are appropriate candidates for more specialized testing. A simple, inexpensive radiopaque marker study will identify STC. Pelvic floor dysfunction needs to be excluded by performing anorectal manometry and a balloon expulsion study; if confirmed, defecography will solidify the diagnosis and evaluate anatomic defects. Patients with proven pelvic floor dysfunction, if the symptoms are severe enough, should be considered for biofeedback. However, this requires an extensive program of therapy. Rarely, the anorectal inhibitory reflex will be absent, and further evaluation for Hirschsprung's disease is indicated.

Patients with colonic inertia should be treated with aggressive laxative programs (e.g., more saline laxatives, stimulant agents, lactulose, or PEG solutions). Truly refractory patients may be considered for surgery, although few will qualify after more extensive physiologic studies.

Many patients will have normal study results. Most will meet criteria for constipation-predominant IBS. The hope is that most of these people can be managed with laxatives and reassurance. As with other functional gastrointestinal disorders, psychological conditions need to be considered as contributing factors. Key to their adequate management is identification of the predominant symptom. Is this constipation or the associated symptoms (bloating, pain, nausea, etc.)?

Unfortunately, the clinical effectiveness and the cost-effectiveness of our algorithmic approach have not been assessed. The structural evaluation, at least in older patients, is likely cost effective on the basis of identifying colon cancer and adenomatous polyps. Laxatives, biofeedback, and surgery have all been shown to be effective in treating selected patients. Community-based physicians will likely do the evaluation sequentially, whereas tertiary centers, for patient convenience, may need to test more simultaneously. Many of the specific points of our algorithms may be debated, and different algorithms certainly have not been compared for clinical or cost benefits. The goal of this review was to guide practicing gastroenterologists through rational and efficacious approaches to patients with constipation.

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Acknowledgements 

The authors thank E. P. Bouras, M. Camilleri, and members of the Mayo Clinic Motility Interest Group for their assistance in developing the algorithms.

The Clinical Practice and Practice Economics Committee acknowledges the following individuals whose critiques of this review paper provided valuable guidance to the authors: John Johanson, M.D., Arnold Wald, M.D., and William Whitehead, Ph.D.

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