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Evaluation and treatment of constipation. (Clinical Update).

Constipation is an often-overlooked problem in primary care practice. It deserves careful evaluation, including consideration of the many possible causes and appropriate diagnostic testing. Fortunately, most patients respond well to conservative measures.

Constipation prompts a visit to a physician by 1.2% of the US population every year (although most persons with constipation do not seek the assistance of a physician). (1) The prevalence of constipation increases with age, and is more common among women than men in all age groups. (2,3) It is more frequent among non-whites, and more frequent in colder, poorer, and rural states. (4)

The definition of constipation varies substantially among patients, clinicians, and researchers, and includes infrequent bowel movements, difficult evacuation of feces, inability to defecate at will, and hard feces. Interestingly, the actual frequency of bowel movements does not change with age even when controlled for laxative use--evidence that the meaning of the term constipation involves more than just frequency of bowel movements. (5)

ETIOLOGY

Constipation is caused by a heterogeneous and often overlapping group of disorders. The undigested food that reaches the colon is mixed with fluid and electrolytes, bacteria, and gas. Normal colonic function requires absorption of water, a coordinated combination of segmental contractions that mix stool, propagation of contractions that move feces over short distances, and high-amplitude contractions that move fecal waste longer distances. Defecation entails a synchronized combination of voluntary contraction of striated muscle and involuntary smooth muscle contraction. Anything that limits the fluid content in fecal waste, interferes with the movement of feces through the colon, or interferes with defecation can cause constipation.

Constipation may be classified as primary or secondary, which emphasizes the need to identify and treat underlying systemic disorders before proceeding with the gastrointestinal evaluation (Table 1). However, constipation is often multifactorial in origin. Irritable bowel syndrome (59%) is the most common primary cause of severe intractable constipation, followed by isolated pelvic floor dysfunction (25%), isolated slow-transit constipation (5%), and combined slow-transit constipation and pelvic floor dysfunction (2%). (6) In a study of 190 patients in whom irritable bowel syndrome and other identifiable causes of severe constipation were excluded, 59% had disordered defecation, 27% had slow-transit constipation, and 6% had a combination of these 2 causes. No pathology was identified in about 8% of these patients. (7)

DIAGNOSIS

History, physical examination, and baseline laboratory testing identify most secondary causes of constipation (Table 1). Patients in whom no secondary cause is found should undergo colonoscopy, or barium enema and flexible sigmoidoscopy to identify any obstructive lesions. Red flags that suggest significant organic disease include weight loss, frequent nocturnal awakening due to symptoms, blood mixed in stool, and a family history of colon cancer.

A therapeutic trial of a high-fiber diet (or fiber supplements) with or without mild laxatives is reasonable if no secondary or obstructive cause is present. If these measures fail. or if the patient has recurrent constipation, more extensive evaluation is required. Patients in whom a gynecologic cause of constipation is suspected should also be considered for a therapeutic trial. Such a trial may reveal that the gynecologic problem is in fact unrelated to the constipation. If the trial fails, further diagnostic testing to look for any obstructive lesion may be undertaken.

History

The basic diagnostic evaluation of constipation begins by clarifying what the patient means by constipation, eliciting associated symptoms that may identify a secondary cause of constipation, and establishing the duration of constipation. A diary of the frequency and ease of defecation, and firmness of stools, may confirm the presence of constipation or identify the patient's misconceptions about normal bowel habits. (8)

Acute onset of symptoms, constipation after the age of 50, or progressive symptoms suggest an organic cause. Onset of symptoms in childhood suggests a congenital or emotional/psychological disorder. Symptoms associated with secondary causes of constipation include abdominal pain (especially if it awakens the patient from sleep), nausea, vomiting, melena, hematochezia, weight loss, hair loss, and cold intolerance. The presence of rectal pain or urinary stress incontinence suggests the possibility of disordered defecation.

A history of metabolic, neurologic, myopathic, or rheumatologic disease suggests secondary causes of constipation. The patient should also be questioned carefully to identify a history of anorexia nervosa, bulimia, or depression with associated constipation. (9,10) A careful review of prescription and over-the-counter medications may identify drug-induced constipation. The patient's dietary habits and level of physical activity should be determined, although the evidence from controlled trials linking constipation with diet and activity is weak at best. Prior travel to Central or South America should raise the possibility of Chagas' disease (American trypanosomiasis).

Irritable bowel syndrome is suggested by the presence of postprandial cramps, excessive "gas," abdominal pain or bloating relieved by defecation, constipation alternating with diarrhea, passage of mucus, or a feeling of incomplete evacuation. The Manning Criteria can help identify patients with a low, intermediate, or high risk of irritable bowel syndrome (Table 2). (11)

Pelvic floor dysfunction should be considered when a patient reports the need to manually remove stool, apply perineal pressure (or vaginal pressure in women) to defecate, or strain excessively to evacuate stool. It should also be considered in patients who report difficulty evacuating soft or liquid stools.

Physical examination

Abdominal distention and tenderness suggest the possibility of an obstructive lesion of the intestinal tract. A rectal examination is necessary to search for stool with gross or occult blood, loss of rectal tone, anal fissure, or altered rectal tone. Laxity during simulated defecation or loss of anal reflex suggests neurogenic dysfunction. A rectocele can be easily identified by observing the posterior vaginal wall during simulated defecation.

Diagnostic tests

A complete blood count, serum electrolytes, serum calcium, blood glucose, blood urea nitrogen, and thyroid-stimulating hormone should be ordered to identify secondary causes of constipation. In the absence of abdominal distention or pain, abdominal radiographs are unlikely to be helpful in the differential diagnosis.

No evidence from outcomes studies suggests that colonoscopy is superior to barium enema for evaluation of constipation. However, colonoscopy may be preferable in patients who have constipation and are coincidentally at risk of colon cancer or irritable bowel syndrome. This would include patients who are 50 years of age or older, as well as those who have anemia, abdominal pain or distention, gross or occult blood in the stool, weight loss, or a family history of colon cancer. Barium enema with or without flexible sigmoidoscopy is appropriate in younger patients who are not at risk for colon cancer. Children and adolescents should have a barium enema to rule out Hirschsprung's disease and idiopathic megarectum.

Expanded diagnostic testing may be necessary for patients in whom there is no identifiable cause following initial evaluation and in whom initial treatment (lifestyle changes, education, and judicious use of bulk or osmotic laxatives) fails. (12) This includes colonic transit time, anorectal manometry, balloon expulsion test, and barium defecography. Primary care physicians may wish to refer patients requiring this kind of evaluation to a gastroenterologist.

TREATMENT

Bulk, saline, osmotic, and stimulant laxatives as well as enemas, suppositories, behavioral therapy, and surgery all have a place in the treatment of constipation (Table 3). However, most patients with constipation will respond to lifestyle and dietary changes.

It is important to advise patients to avoid excessive use of laxatives and to realize that it may take 4 to 6 weeks for normal bowel function to return after excessive use is stopped.

Patients whose constipation is not relieved by lifestyle and diet changes may benefit from judicious use of a laxative. There is little evidence to suggest that bulk laxatives are more advantageous than other classes of laxatives (13,14); however, because of their safety and other possible health benefits, it is reasonable to start treatment of chronic constipation with a bulk laxative. A saline or osmotic laxative can be added if the bulk laxative fails. Stimulant laxatives should be reserved for cases in which bulk, saline, and osmotic laxatives are ineffective. The emollient laxative, mineral oil, should be avoided because it has been associated with lipoid aspiration pneumonia. Docusate, an emollient laxative, has questionable efficacy and has a limited place in the management of constipation. (15)

Few patients require extensive intervention such as surgery or behavioral therapy. Individual treatment options, including management of fecal impaction, are discussed below.

Lifestyle changes and patient education

Lifestyle changes and patient education are important components in the management of constipation. In fact, reassurance and instruction will be the primary treatment for many patients. A suggested patient education handout, "What You Should Know About Constipation," is included with this article on page 560. (For your convenience, it may he freely duplicated and distributed.)

Suggested lifestyle changes include moderate physical activity, increased fluid intake, increased dietary fiber, and sitting on the toilet about 15-20 minutes after breakfast (taking advantage of the gastrocolic reflex). In selected patients, these changes may he useful, although specific benefits of moderate physical activity and increased fluid intake have not been conclusively proven.

Bulk laxatives

Wheat bran is one of the best and least expensive bulk laxatives. Methylcellulose (eg, Citrucel), psyllium (eg, Metamucil), and polycarbophil (eg, FiberCon) are bulk laxatives that are safe, more refined, and more concentrated than wheat bran, but they are also more expensive. Combined with diet and liquids, bulk laxatives are the most effective and "natural" long-term treatment for constipation. However, their slow onset of action (between 12 and 72 hours) limits their usefulness in acute management of constipation.

Saline laxatives

The saline laxatives include magnesium citrate (eg, Citroma) and magnesium hydroxide (eg, Milk of Magnesia). These agents decrease colonic transit time by stimulating cholecystokinin and draw fluid into the colon by their osmotic effect. Their rapid onset of action (between 30 minutes and 3 hours) makes saline laxatives an excellent choice for acute management of constipation. These laxatives commonly cause abdominal cramping and, in patients with renal failure, may cause magnesium toxicity. Nevertheless, saline laxatives are generally safe and effective.

Osmotic laxatives

Polyethylene glycol (eg, MiraLax) is an effective new osmotic laxative. Rapid onset of action (between 24 and 48 hours) makes an osmotic a good choice for patients who have chronic constipation that fails to respond to bulk and saline laxatives. Polyethylene glycol is equally effective, but better tolerated than the older osmotics, lactulose and sorbitol. (16) Because it is not fermented, gas and cramps are minimal. Lactulose (eg, Chronulac) and sorbitol, which are poorly absorbed sugars, likewise have rapid onset of action, but flatulence and abdominal distention may limit tolerance. Sorbitol is generally less expensive than lactulose.

Stimulant laxatives

The oral stimulant laxatives include diphenylmethanes, the antraquinones, and castor oil (eg, Emulsoil). They are more potent than bulk or osmotic laxatives, but long-term use is safe if limited to 3 days per week. Bisacodyl (eg, Dulcolax), a diphenylmethane, alters electrolyte transportation within intestinal mucosa and stimulates peristalsis. These actions may cause abdominal cramping and hypokalemia. Cascara (mildest), senna (eg, Senokot), and aloe (strongest) are anthraquinones, which are laxatives with actions and side effects similar to bisacodyl. These agents may cause a benign, reversible pigmentation of the colon (melanosis coli). It has been suggested that chronic use of these agents may damage the enteric nervous system, but a causal relationship has not been clearly established. The most prudent approach is to limit use of stimulant laxatives to constipation flint is refractory to other laxatives.

Enemas and suppositories

Enemas and suppositories stimulate colonic contractions and soften stools. Water, saline, soap suds, hypertonic sodium phosphate, and mineral oil are used as enemas. Acute water intoxication can occur with water enemas, especially in infants, children, and the elderly, if they have difficulty evacuating the water. Phosphate enemas may cause hyperphosphatemia and hypocalcemic tetany in these patients and should therefore be used with caution in most patients and should not be used in children 3 years of age or younger. Glycerin and bisacodyl are stimulant suppositories that are clinically effective. Bisacodyl and soap suds enemas cause changes in the epithelium of the rectum, and the effect of glycerin on rectal mucosa is unclear. Therefore, these agents should only be used episodically. Mineral oil enemas are used to soften hardened stool in the rectal ampulla.

Other treatment options

More aggressive measures may be necessary for specific types of constipation. These include behavioral therapy and biofeedback for pelvic floor dysfunction, and surgery for slow-transit constipation or Hirschsprung's disease.

Investigative pharmacologic treatments for constipation include agents that increase colonic contractions (prokinetic drugs) and prostaglandins. These agents have had limited efficacy and troublesome side effects. Therefore, at this time these drugs have limited usefulness in the treatment of constipation.

FECAL IMPACTION

The management of fecal impaction begins with complete evacuation of the colon. Initially, patients with hard stool in the rectum may be given mineral oil retention enemas followed by manual disimpaction. Prior to further treatment, it is important to obtain an abdominal radiograph to rule out mechanical bowel obstruction. If there is no mechanical bowel obstruction, evacuation of the impaction can be accomplished with oral polyethylene glycol (eg, GoLytely) until clear (up to 8 liters or more may be required for complete evacuation). (16) Administration of twice-daily enemas for 3 days or more is an acceptable alternative to oral polyethylene glycol. Lifestyle changes, bulk laxatives, saline, osmotic laxatives, and enemas should be used to maintain regular defecation after the colon has been cleansed. It is reasonable to attempt to withdraw laxatives after several months of regular bowel habits.
TABLE 1
Primary and secondary
causes of constipation

Primary causes           Secondary causes

Functional               Connective tissue
  Idiopathic             disease
  Irritable bowel          Amyloidosis
    syndrome               Systemic sclerosis
  Pelvic dyssynergia     Lifestyle
    (anismus)              Dehydration
  Slow-transit             Inadequate dietary fiber
    constipation           Sedentary lifestyle
Neuropathic                Voluntary suppression
  Chagas' disease            of defecation
  Congenital anal        Medications
    sphincter myopathy     Anticholinergics
  Hirschsprung's           Anticonvulsants
    disease                Antidepressants
  Hyperganglionosis        Antihistamines
  Spinal cord injury       Antiparkinsonian drugs
Obstructive                Antipsychotics
  Anal stenosis            Antacids
  Crohn's disease          Calcium-channel
  Colon cancer               blockers
  Compression by           Calcium supplements
    tumor                    Diuretics
  Stricture                Iron supplements
Gynecologic                Laxatives (chronic abuse)
  Large rectocele          NSAIDs
  Pelvic relaxation        Opiates
                         Metabolic/endocrine
                           Diabetes mellitus
                           Heavy metal poisoning
                           Hypercalcemia
                           Hypokalemia
                           Hypothyroidism
                           Hypomagnesemia
                           Porphyria
                           Uremia
                         Neuropathic
                           Autonomic neuropathy
                           Multiple sclerosis
                           Paraneoplastic
                             neuropathy
                           Parkinson's disease
                         Psychological
                           Depression
                           Eating disorders
                           Situational stress
TABLE 2 Manning Criteria for the diagnosis
of irritable bowel syndrome (11)

Count the number of symptoms that occur daily:

* Abdominal pain relieved by defecation

* More frequent stools with the onset of pain

* Looser stools with the onset of pain

* Passage of mucus

* Sensation of incomplete evacuation

* Visible abdominal distention

With fewer than 2 symptoms daily, irritable bowel syndrome is unlikely.

With 2 or 3 symptoms daily, irritable bowel syndrome is an
intermediate probability.

With 4 or more symptoms daily, irritable bowel syndrome is a
significant probability.
TABLE 3
aTherapeutic options for the
management of constipation

Type                           Example             Dose

Lifestyle
   Increase liquids            Mineral water       2 liters/day
     in diet  (17)
   Increase fiber              Dietary fiber       25 g/day
     in diet (17)
   Moderate                    Unspecified         Unspecified
     physical activity
   Eliminate excessive              --                 --
     use of laxatives

Bulk
   Wheat bran (18)                  --             20 g/day
   Psyllium (19)               Metamucil           7 g/day
   Methylcellulose (20)        Citrucel            4-6 g/day
   Calcium                     FiberCon            4-6 g/day
     polycarbophil (21)

Saline (13,14)
   Magnesium citrate           Citroma             200 mL/day
   Magnesium                   Milk of             2.4 g/day
     hydroxide                   Magnesia

Osmotic
   Polyethylene                MiraLax             17 g/day
     glycol (22)
   Sorbitol (23)               Generic             20 g/day
   Lactulose (24)              Chronulac           30 mL/day

Stimulant (13,14)
   Castor oil                  Emulsoil            15-60 mL/day
   Bisacodyl                   Dulcolax            30 mg/day
   Cascara                     Generic             2-5 mL/day
   Senna                       Senokot             17-34 mg/day
   Aloe                        Generic             50-200 mg/day

Enema (12)
   Tap water                       --              500 mL/day
   Saline                      Generic             500 mL/day
   Phosphate                   Fleets              4.5 oz/day
   Mineral oil retention       Generic             100-250 mL/day

Suppositories (12)
   Bisacodyl                   Generic             10 mg/day
   Glycerin                    Generic             3 g/day

Behavioral therapy
   Biofeedback (25)            Pelvic floor
                                 muscle training
   Regular time on             15-20 minutes
     toilet after breakfast      after breakfast

Surgery
   Severe refractory           Subtotal
     constipation (26)           colectomy

                                   Evidence
Type                                level *

Lifestyle
   Increase liquids                    A
     in diet  (17)
   Increase fiber                      A
     in diet (17)
   Moderate                            D
     physical activity
   Eliminate excessive                 D
     use of laxatives

Bulk
   Wheat bran (18)                     A
   Psyllium (19)                       A
   Methylcellulose (20)                A
   Calcium                             A
     polycarbophil (21)

Saline (13,14)
   Magnesium citrate                   A
   Magnesium                           A
     hydroxide

Osmotic
   Polyethylene                        A
     glycol (22)
   Sorbitol (23)                       A
   Lactulose (24)                      A

Stimulant (13,14)
   Castor oil                          A
   Bisacodyl                           A
   Cascara                             A
   Senna                               A
   Aloe                                A

Enema (12)
   Tap water                           D
   Saline                              D
   Phosphate                           D
   Mineral oil retention               D

Suppositories (12)
   Bisacodyl                           D
   Glycerin                            D

Behavioral therapy
   Biofeedback (25)                    A

   Regular time on
     toilet after breakfast            D

Surgery
   Severe refractory                   A
     constipation (26)

* A = Evidence from one or more randomized controlled trials.

B = Evidence from observational studies (case-control or cohort).

C = Case series only.

D = Expert opinion, physiology, bench research only.


REFERENCES

(1.) Sonnenberg A, Koch T. Physician visits in the United States for constipation. Dig Dis Sci 1989; 34:606-11.

(2.) Sonnenberg A, Koch T. Epidemiology of constipation in the United States. Dis Colon Rectum 1989; 32:1-8.

(3.) Johanson JF, Sonnenberg A, Koch T. Clinical epidemiology of chronic constipation. J Clin Gastroenterol 1989; 11:525.

(4.) Johanson JF. Geographic distribution of constipation in the United States Am J Gastroenterol 1998; 93:188-91.

(5.) Harari D, Gurwitz J, Avorn J, Bohn R, Minaker K. Bowel habit in relation to age and gender: findings from the National Health Interview Survey and clinical implications. Arch Intern Med 1996; 156:315-20.

(6.) Nyam D, Pemberton JH, Ilstrup DM, et al. Long-term results of surgery for chronic constipation. Dis Colon Rectum 1997; 40:273-7.

(7.) Koch A, Voderholzer W, Klauser A, Muller-Lissner SA. Symptoms in chronic constipation Dis Colon Rectum 1997; 40:902-6.

(8.) Ashraf W, Park F, Lof J, et al. An examination of the reliability of reported stool frequency in the diagnosis of idiopathic constipation. Am J Gastroenterol 1996; 91:26-32.

(9.) Kamal N, Chami T, Andersen A, el al. Delayed gastrointestinal transit times in anorexia nervosa and bulimia nervosa. Gastroenterology 1991; 101:1320-4.

(10.) Garvey M. Noyes R Jr, Yates W. Frequency of constipation in major depression: relationship to other clinical variables. Psychosomatics 1990; 31:204-6.

(11.) Manning AP, Thompson WG, Heaton KW, Morris AF. Towards a positive diagnosis of the irritable bowel. BMJ 1978; 2:653-4.

(12.) Locke GR, Pemberton JH, Phillips SF. AGA technical review on constipation. Gastroenterology 2000: 119:1766-78.

(13.) Tramonte SM, Brand MB, Mulrow CD, et al. The treatment of chronic constipation in adults. A systematic review. J Gen Intern Med 1997; 12:15-24.

(14.) Petticrew M, Watt I, Brand M. What's the "best buy" for treatment of constipation? Results of a systematic review of the efficacy and comparative efficacy of laxatives in the elderly. Br J Gen Pract 1999; 49:387-93.

(15.) Hurdon V, Viola R, Schroder C. How useful is docusate in patients at risk for constipation? A systematic review of the evidence in the chronically ill. J Pain Symptom Manage 2000; 19:130-6.

(16). Tiongco F, Tsang T, Pollack J. Use of oral GoLytely solution in relief of refractory fecal impaction. Dig Dis Sci 1997; 42:1454-7.

(17.) Anti M, Pignataro G, Armuzzi A, et al. Water supplementation enhances the effect of high-fiber diet on stool frequency and laxative consumption in adult patients with functional constipation. Hepatogastroenterology 1998; 45:727-32.

(18.) Graham D, Moser S, Estes M. The effect of bran on bowel function in constipation. Gastroenterology 1982; 77: 599-603.

(19.) Marlett JA, Li BU, Patrow CJ, Bass P. Comparative laxation of psyllium with and without senna in an ambulatory constipated population Am J Gastroenterol 1987; 82:333-7.

(20.) Hamilton J, Wagner J, Burdick B, Bass P. Clinical evaluation of methylcellulose as a bulk laxative. Dig Dis Sci 1988: 33:993-8.

(21.) Bass P, Clark C, DoPico GA. Comparison of the laxative efficacy and patient preference of calcium polycarbophil and psyllium suspension. Curr Ther Res Clin Exp 1988; 43:770-4.

(22.) Attar A, Lemann M, Ferguson A, et al. Comparison of a low-dose polyethylene glycol electrolyte solution with lactulose for treatment of chronic constipation. Gut 1999: 44:226-30.

(23.) Lederle F, Busch D, Mattox K, West M, Aske D. Cost-effective treatment of constipation in the elderly: a randomized double-blind comparison of sorbitol and lactulose. Am J Med 1990; 89:597-601.

(24.) Sanders JF. Lactulose syrup assessed in a double-blind study of elderly constipated patients. J Am Geriatr Soc 1978; 26:236-9.

(25.) Koustomanis D, Lennard-Jones J, Roy A, Kamm M. Controlled randomized trial of visual biofeedback versus muscle training without a visual display for intractable constipation. Gut 1995; 37:95-9.

(26.) Nyman DC, Pemberton JH, Ilstrup DM, et al. Long-term results of surgery for chronic constipation. Dis Colon Rectum 1997; 40:273-9.

This special section in The Journal of Family Practice is provided by an unrestricted educational grant from Braintree Laboratories, manufacturer of Miralax. The sponsor selected the topic but had no role in author or editor selection, or in development of the content. The author and editor received a stipend for this work. The author and editor report no competing interests.

STEVEN A. DOSH, MD, Department of Family Practice, Michigan State University, 3409 Ludington, Escanaba, MI 49829. E-mail: doshstev@msu.edu
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