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Constipation is difficult or infrequent passage of stool, hardness of stool, or a feeling of incomplete evacuation.

Many people incorrectly believe that daily defecation is necessary and complain of constipation if stools occur less frequently. Others are concerned with the appearance (size, shape, color) or consistency of stools. Sometimes the major complaint is dissatisfaction with the act of defecation or the sense of incomplete evacuation after defecation. Constipation is blamed for many complaints (abdominal pain, nausea, fatigue, anorexia) that are actually symptoms of an underlying problem (eg, irritable bowel syndrome, depression). Patients should not expect all symptoms to be relieved by a daily bowel movement, and measures to aid bowel habits should be used judiciously.

Obsessive-compulsive patients often feel the need to rid the body daily of “unclean” wastes. Such patients often spend excessive time on the toilet or become chronic users of cathartics.

Etiology

Acute constipation suggests an organic cause, whereas chronic constipation may be organic or functional (see Table 1: Approach to the Patient With Lower GI Complaints: Causes of Constipation).

In many patients, constipation is associated with sluggish movement of stool through the colon. This delay may be due to drugs, organic conditions, or a disorder of defecatory function (ie, pelvic floor dysfunction). Patients with disordered defecation do not generate adequate rectal propulsive forces, do not relax the puborectalis and the external anal sphincter during defecation, or both. Irritable bowel syndrome (IBS) refers to patients who have symptoms (eg, abdominal discomfort and altered bowel habits) but generally normal colonic transit and anorectal functions. However, IBS-disordered defecation may coexist.

Excessive straining, perhaps secondary to pelvic floor dysfunctions, may contribute to anorectal pathology (eg, hemorrhoids, anal fissures, and rectal prolapse) and possibly even to syncope. Fecal impaction, which may cause or develop from constipation, is also common in elderly patients, particularly with prolonged bed rest or decreased physical activity. It is also common after barium has been given by mouth or enema.

Changes with aging: Constipation is common in elderly people because of low-fiber diets, lack of exercise, coexisting medical conditions, and use of constipating drugs. Many elderly people have misconceptions about normal bowel habits and use laxatives regularly. Other changes that predispose the elderly to constipation include increased rectal compliance and impaired rectal sensation (such that larger rectal volumes are needed to elicit the desire to defecate).

Table 1
Causes of Constipation Causes Examples Acute constipation* Bowel obstruction Volvulus, hernia, adhesions, fecal impaction Adynamic ileus Peritonitis, major acute illness (eg, sepsis), head or spinal trauma, bed rest Drugs Anticholinergics (eg, antihistamines, antipsychotics, antiparkinsonian drugs, antispasmodics), cations (iron, aluminum, Ca, barium, bismuth), opioids, Ca channel blockers, general anesthesia Chronic constipation* Colonic tumor Adenocarcinoma of sigmoid colon Metabolic disorders Diabetes mellitus, hypothyroidism, hypocalcemia or hypercalcemia, pregnancy, uremia, porphyria CNS disorders Parkinson's disease, multiple sclerosis, stroke, spinal cord lesions Peripheral nervous system disorders Hirschsprung's disease, neurofibromatosis, autonomic neuropathy Systemic disorders Systemic sclerosis, amyloidosis, dermatomyositis, myotonic dystrophy Functional Slow-transit constipation, irritable bowel syndrome, pelvic floor dysfunction (functional defecatory disorders) *There is some overlap between acute and chronic causes of constipation. In particular, drugs are common causes of chronic constipation.

Evaluation

History: A lifetime history of the patient's stool frequency, consistency, need to strain or use perineal maneuvers (eg, pushing on the perineum, gluteal region, or recto-vaginal wall) during defecation, and satisfaction after defecation should be obtained, including frequency and duration of laxative or enema use. Some patients deny previous constipation but, when questioned specifically, admit to spending 15 to 20 min per bowel movement. The presence, amount, and duration of blood in the stool should also be elicited.

Symptoms of metabolic (eg, hypothyroidism, diabetes mellitus) and neurologic disorders (eg, spinal cord injury) and systemic symptoms (eg, weight loss) should also be sought. Prescription and nonprescription drug use should be assessed, with specific questioning about anticholinergic and opioid drugs.

Physical examination: A general examination is done to look for signs of systemic disease, including fever and cachexia. Abdominal masses should be sought by palpation. A rectal examination should be done not only for fissures, strictures, blood, or masses (including fecal impaction) but also to evaluate anal resting tone (the puborectalis “lift” when patients squeeze the anal sphincter), perineal descent during simulated evacuation, and rectal sensation. Patients with defecatory disorders may have increased anal resting tone (or anismus), reduced (ie, < 2 cm) or increased (ie, > 4 cm) perineal descent, and/or paradoxical contraction of the puborectalis during simulated evacuation.

Red flags: Certain findings raise suspicion of a more serious etiology of chronic constipation.

• Distended, tympanitic abdomen
• Vomiting
• Blood in stool
• Weight loss
• Severe constipation of recent onset/worsening in elderly patients

Interpretation of findings: Certain symptoms (eg, a sense of anorectal blockage, prolonged or difficult defecation), particularly when associated with abnormal (ie, increased or reduced) perineal motion during simulated evacuation, suggest a defecatory disorder. A tense, distended, tympanitic abdomen, particularly when there is nausea and vomiting, suggests mechanical obstruction.

Patients with irritable bowel syndrome typically have abdominal pain with disordered bowel habits (see Irritable Bowel Syndrome (IBS)). Chronic constipation with modest abdominal discomfort in the setting of long-standing laxative use suggests slow-transit constipation. Acute constipation coincident with the start of a constipating drug in patients without red flags suggests the drug is the cause. New-onset constipation that persists for weeks or occurs intermittently with increasing frequency or severity, in the absence of a known cause, suggests colonic tumor or other causes of partial obstruction. Excessive straining or prolonged or unsatisfactory defecation, with or without anal digitation, suggests a defecatory disorder. Patients with fecal impaction may have cramps and may pass watery mucus or fecal material around the impacted mass, mimicking diarrhea (paradoxic diarrhea).

Testing: Testing is guided by clinical presentation.

Constipation with a clear etiology (drugs, trauma, bed rest) may be treated symptomatically without further study. Patients with symptoms of bowel obstruction require flat and upright abdominal x-rays, possibly a water-soluble contrast enema to evaluate for colonic obstruction, and possibly a CT scan or barium x-ray of the small intestine (see also Acute Abdomen and Surgical Gastroenterology: Diagnosis). Most patients without a clear etiology should have sigmoidoscopy or colonoscopy and a laboratory evaluation (CBC, thyroid-stimulating hormone, fasting glucose, electrolytes, and Ca).

Further tests are usually reserved for patients with abnormal findings on the previously mentioned tests or who do not respond to symptomatic treatment. If the primary complaint is infrequent defecation, colonic transit times should be measured with radiopaque markers or scintigraphy. If the primary complaint is difficulty with defecation, anorectal manometry and rectal balloon expulsion should be assessed.

Treatment

• Possibly discontinuation of causative drugs (some may be necessary)
• Increase in dietary fiber
• Possibly trial with a brief course of osmotic laxatives

Any identified conditions should be treated.

Agents used to treat constipation are summarized in Table 2: Approach to the Patient With Lower GI Complaints: Agents Used to Treat Constipation. Laxatives should be used judiciously. Some (eg, phosphate, bran, cellulose) bind drugs and interfere with absorption. Rapid fecal transit may rush some drugs and nutrients beyond their optimal absorptive locus. Contraindications to laxative and cathartic use include acute abdominal pain of unknown origin, inflammatory bowel disorders, intestinal obstruction, GI bleeding, and fecal impaction.

Diet and behavior: The diet should contain enough fiber (typically 15 to 20 g/day) to ensure adequate stool bulk. Vegetable fiber, which is largely indigestible and unabsorbable, increases stool bulk. Certain components of fiber also absorb fluid, making stools softer and facilitating their passage. Fruits and vegetables are recommended sources, as are cereals containing bran. Fiber supplementation is particularly effective in treating normal-transit constipation but is not very effective for slow-transit constipation or defecatory disorders.

Behavioral changes may help. The patient should try to move the bowel at the same time daily, preferably 15 to 45 min after breakfast, because food ingestion stimulates colonic motility. Initial efforts at regular, unhurried bowel movements may be aided by glycerin suppositories.

Explanation is important, but it is difficult to convince obsessive-compulsive patients that their attitude toward defecation is abnormal. Physicians must explain that daily bowel movements are not essential, that the bowel must be given a chance to function, and that frequent use of laxatives or enemas (> once/3 days) denies the bowel that chance.

Table 2
Agents Used to Treat Constipation Type Agent Dosage Side Effects Fiber* Bran Up to 1 cup/day Bloating, flatulence, iron and Ca malabsorption Psyllium Up to 10–15 g/day in divided doses of 2.5–7.5 g Bloating, flatulence Methylcellulose Up to 6–9 g/day in divided doses of 0.45–3 g Less bloating than with other fiber agents Ca polycarbophil Some Trade Names FIBER-LAX KONSYL FIBER CAPLETS Click for Drug Monograph 2–6 tablets/day Bloating, flatulence Emollients Docusate Some Trade Names COLACE SURFAK Click for Drug Monograph Na 100 mg bid or tid Ineffective for severe constipation   Glycerin 2–3 g suppository once/day Rectal irritation   Mineral oil 15–45 mL po once/day Lipid pneumonia, malabsorption of fat-soluble vitamins, dehydration, fecal incontinence Osmotic agents Sorbitol 15–30 mL po of 70% solution once/day or bid; 120 mL rectally of 25–30% solution Transient abdominal cramps, flatulence Lactulose Some Trade Names CEPHULAC CHRONULAC KRISTALOSE Click for Drug Monograph 10–20 g (15–30 mL) once/day up to qid Same as for sorbitol Polyethylene glycol 17 g daily Fecal incontinence (related to dosage) Mg Mg sulfate 15–30 g/day or bid; milk of Mg, 30–60 mL/day; Mg citrate Some Trade Names CITROMA , 150–300 mL/day (up to 360 mL) Mg toxicity, dehydration, abdominal cramps, fecal incontinence Na phosphate 10 g po once as bowel preparation Rare cases of acute renal failure Stimulants Anthraquinones Depends on brand used Abdominal cramps, dehydration, melanosis coli, malabsorption; possible deleterious effects on intramural nerves   Bisacodyl Some Trade Names DULCOLAX Click for Drug Monograph 10 mg suppositories up to 3 times/wk; 5–15 mg/day po Fecal incontinence, hypokalemia, abdominal cramps, rectal burning with daily use of suppository form   Lubiprostone Some Trade Names AMITIZA Click for Drug Monograph † 24 μg po bid with food Nausea, particularly on empty stomach; approved for long-term use   Tegaserod Some Trade Names ZELNORM Click for Drug Monograph ‡ 6 mg po bid Diarrhea, headache, heart attack, stroke Enemas Mineral oil/olive oil retention 100–250 mL/day rectally Fecal incontinence, mechanical trauma   Tap water 500 mL rectally Mechanical trauma   Phosphate 60 mL rectally Accumulated damage to rectal mucosa, hyperphosphatemia, mechanical trauma   Soapsuds 1500 mL rectally Accumulated damage to rectal mucosa, mechanical trauma * The dose of fiber supplements should be gradually increased over several weeks to the recommended dose. † Available by prescription only. ‡ Available under a restricted-use program. Adapted from Romero Y, Evans JM, Fleming KC, Phillips SF: Constipation and fecal incontinence in the elderly population. Mayo Clinic Proceedings 71:81–92, 1996; by permission.

Types of laxatives: Bulking agents (eg, psyllium, Ca polycarbophil Some Trade Names
FIBER-LAX
KONSYL FIBER CAPLETS
Click for Drug Monograph
, methylcellulose) act slowly and gently and are the safest agents for promoting elimination. Proper use involves gradually increasing the dose—ideally taken tid or qid with sufficient liquid (eg, 500 mL/day of extra fluid) to prevent impaction—until a softer, bulkier stool results. Bloating may be reduced by gradually titrating the dose of dietary fiber to the recommended dose, or by switching to a synthetic fiber preparation such as methylcellulose.

Osmotic agents contain poorly absorbed polyvalent ions (eg, Mg, phosphate, sulfate), polymers (eg, polyethylene glycol) or carbohydrates (eg, lactulose Some Trade Names
CEPHULAC
CHRONULAC
KRISTALOSE
Click for Drug Monograph
, sorbitol) that remain in the bowel, increasing intraluminal osmotic pressure and thereby drawing water into the intestine. The increased volume stimulates peristalsis. These agents usually work within 3 h.

In general, osmotic laxatives are reasonably safe even when used regularly. However, Na phosphate should not be used for bowel cleansing because it may rarely cause acute renal failure even after a single use for bowel preparation. These events occurred primarily in elderly patients, those with preexisting renal disease, and those who were taking drugs that affect renal perfusion or function (eg, diuretics, ACE inhibitors, angiotensin II receptor blockers). Also, Mg and phosphate are partially absorbed and may be detrimental in some conditions (eg, renal insufficiency). Na (in some preparations) may exacerbate heart failure. In large or frequent doses, these drugs may upset fluid and electrolyte balance. Another approach to cleansing the bowel for diagnostic tests or surgery or sometimes for chronic constipation uses large volumes of a balanced osmotic agent (eg, polyethylene glycol–electrolyte solution) given orally or via NGT.

Secretory or stimulant cathartics (eg, phenolphthalein, bisacodyl Some Trade Names
DULCOLAX
Click for Drug Monograph
, anthraquinones, castor oil, anthraquinones) act by irritating the intestinal mucosa or by directly stimulating the submucosal and myenteric plexus. Although phenolphthalein was withdrawn from the US market after animal studies suggested the compound was carcinogenic, there is no epidemiologic evidence of this in humans. Bisacodyl Some Trade Names
DULCOLAX
Click for Drug Monograph
is an effective rescue medication for chronic constipation. The anthraquinones senna Some Trade Names
EX-LAX
SENOKOT
Click for Drug Monograph
, cascara sagrada, aloe, and rhubarb are common constituents of herbal and over-the-counter laxatives. They pass unchanged to the colon where bacterial metabolism converts them to active forms. Side effects include allergic reactions, electrolyte depletion, melanosis coli, and cathartic colon. Melanosis coli is a brownish black colorectal pigmentation of unknown composition. Cathartic colon refers to alterations in colonic anatomy observed on barium enema in patients with chronic stimulant laxative use. It is unclear if cathartic colon, which has been attributed to destruction of myenteric plexus neurons by anthraquinones, is caused by currently available agents or to other neurotoxic agents (eg, podophyllin), which are no longer available. There does not appear to be an increased risk of colon cancer with long-term anthraquinone use.

Enemas can be used, including tap water and commercially prepared hypertonic solutions.

Emollient agents (eg, docusate Some Trade Names
COLACE
SURFAK
Click for Drug Monograph
, mineral oil) act slowly to soften stools, making them easier to pass. However, they are not potent stimulators of defecation. Docusate Some Trade Names
COLACE
SURFAK
Click for Drug Monograph
is a surfactant, which allows water to enter the fecal mass to soften and increase its bulk.

Fecal impaction: Fecal impaction is treated initially with enemas of tap water followed by small enemas (100 mL) of commercially prepared hypertonic solutions (eg, Na phosphate). If these do not work, manual fragmentation and disimpaction of the mass is necessary. This procedure is painful, so perirectal and intrarectal application of local anesthetics (eg, lidocaine Some Trade Names
XYLOCAINE
Click for Drug Monograph
5% ointment or dibucaine Some Trade Names
NUPERCAINAL
Click for Drug Monograph
1% ointment) is recommended. Some patients require sedation.

Key Points

• Drug causes are common (eg, chronic laxative abuse, use of anticholinergic or opioid drugs).
• Be wary of bowel obstruction when constipation is acute and severe.
• Symptomatic treatment is reasonable in the absence of red flags and after excluding pelvic floor dysfunction.

Dyschezia

(Disordered Evacuation; Dysfunction of Pelvic Floor or Anal Sphincters; Functional Defecatory Disorders; Dyssynergia)

Dyschezia is difficulty defecating. Patients sense the presence of stool and the need to defecate but are unable. It results from a lack of coordination of pelvic floor muscles and anal sphincters. Diagnosis requires anorectal testing. Treatment is difficult, but biofeedback may be of benefit.

Etiology

Normally, when a person tries to defecate, rectal pressure rises in coordination with relaxation of the external anal sphincter. This process may be affected by one or more dysfunctions (eg, impaired rectal contraction, excessive contraction of the abdominal wall, paradoxic anal contraction, failure of anal relaxation) of unclear etiology. Functional defecatory disorders may present at any age. In contrast, Hirschsprung's disease, which is due to an absent recto-anal inhibitory reflex, is almost always diagnosed in infancy or childhood.

Symptoms and Signs

The patient may or may not sense that stool is present in the rectum. Despite prolonged straining, evacuation is tedious or impossible, frequently even for soft stool or enemas. Patients may complain of anal blockage and may digitally remove stool from their rectum or manually support their perineum or splint the vagina to evacuate. Actual stool frequency may or may not be decreased.

Diagnosis

Rectal and pelvic examinations may reveal hypertonia of the pelvic floor muscles and anal sphincters. With bearing down, patients may not demonstrate the expected anal relaxation and perineal descent. With excessive straining, the anterior rectal wall prolapses into the vagina in patients with impaired anal relaxation; thus rectoceles are usually a secondary rather than a primary disturbance. Long-standing dyschezia with chronic straining may produce a solitary rectal ulcer or varying degrees of rectal prolapse or excessive perineal descent or an enterocoele. Anorectal manometry and rectal balloon expulsion, occasionally supplemented by defecatory or magnetic resonance proctography, are necessary to diagnose the condition.

Treatment

Because treatment with laxatives is unsatisfactory, it is important to assess anorectal functions in patients with refractory constipation. Biofeedback therapy can improve coordination between abdominal contraction and pelvic floor relaxation during defecation, thereby improving symptoms. However, pelvic floor retraining for defecatory disorders is highly specialized and available at select centers only. A collaborative approach (physiotherapists, dietitians, behavior therapists, gastroenterologists) is necessary.

Last full review/revision October 2007 by Adil E. Bharucha, MBBS, MD

Content last modified October 2007