Constipation is a common complaint of patients presenting to their primary care clinician. In the United States it has been estimated that approximately four hundred million dollars are spent annually on over-the-counter laxatives. In addition, numerous diagnostic studies and workups are performed every year in the evaluation of constipation, but the exact cost of such cannot be estimated. In general, most forms of constipation are idiopathic and have little long-term significance. Though, chronic constipation may have profound impacts with respect to patient’s quality of life and can be associated with other disease states. No true definition exists for constipation . In general, large population studies have suggested that with consumption of an adequate western diet, at least three bowel movements per week are defined as the norm. Constipation, thus, can be defined as a frequency of defecation less than two times a week. In addition to frequency, patients often times will complain of difficulty with straining, change in pattern of bowel frequency and morphology of the stool itself. In normal subjects, daily stool patterns may vary considerably. Hence, quantification of constipation may be difficult for the clinician.

Physiology of Constipation

Constipation primarily consists of delayed transit or disordered movement through the segment of the intestine, primarily localized to the colon. In general, constipation can be classified into idiopathic forms, which predominate the majority of office visit versus underlying physiologic causes. Several disease states are associated with constipation. These include metabolic, endocrine and neurologic disorders. Click on Table I to view lists of several causes of physiologic constipation in patients with systemic illnesses. The most common endocrine cause of constipation is diabetes. Sixty percent of patients with diabetes may report constipation. In addition, constipation has been associated with hypothyroidism, but usually this is mild and will improve with thyroid replacement. Constipation has been associated with pregnancy, and may be related to hormonal changes and the use of iron supplementation. Numerous drugs are associated with constipation and should be excluded as a cause of constipation ( click to Table II). Neurological disorders have long been established as a cause of constipation. A classic model of this is Hirschsprung disease. In Hirschsprung patients there is an absence of the rectosphincteric inhibitory reflex. This is secondary to the absence of the intramural ganglion cells of both the submucosal and myenteric plexuses. These patients demonstrate a classic lack of internal anal sphincter relaxation with rectal distention, which can be proven by anorectal motility. Large rectal biopsies of the rectum of these patients will demonstrate histologic findings with the absence of neurons. Classically these patients are diagnosed in the first decade of life, but adult presentations can occur. Other forms of neurologic causes of constipation may include patients with injury to the lumbosacral spine, patients with meningomyelocele and patients who have had spinal anesthesia.

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Idiopathic Constipation

By far, the majority of patients with constipation have idiopathic constipation. As such, there is no obvious cause for their symptoms. In such patients, there is an absence of associated disease states or definitive pathophysiology. Chronic constipation may be manifested in the pediatric population group. In general, when the disease states have been excluded and chronic idiopathic constipation is considered in these patients, the majority of these patients have probable underlying psychologic factors to be considered. Though, while behavioral problems may be associated with idiopathic constipation in the pediatric population group, this disorder cannot be confused with psychogenic constipation.

In the adult population, constipation in its severe form predominantly is associated with women. Classically, constipation without abdominal pain or bloating differentiates idiopathic constipation from irritable bowel syndrome. Adults with constipation without features of irritable bowel syndrome may complain of infrequent defecation, excessive straining and oftentimes will fail minimal therapeutic interventions. Interestingly, when studied, patients who consult for complaints of constipation and who have been unresponsive to conventional therapeutic intervention, such as increasing fiber content, on colonic transit studies will be shown to have normal colonic movement. The remaining patients when studies will demonstrate true slow colonic transit and hence can be described as having colonic inertia. Interestingly, patients with normal transit times but with complaints of constipation seem to have higher psychologic distress scores as compared to those patients with true colonic inertia, as demonstrated by delayed passage of radiopaque markers.

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Irritable Bowel Syndrome

As stated above, patients with true constipation symptoms must be separated from those with irritable bowel syndrome. Patients with irritable bowel syndrome classically will have complaints of constipation, but with associated features and symptoms of abdominal pain and bloating. Additionally, one must be thoughtful as for other symptoms, as patients with irritable bowel syndrome may complain of dyspepsia and other generalized symptomatic complaints, which are nonspecific.

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Constipation in the Elderly

Constipation in the elderly constitutes a real clinical problem. Oftentimes, these patients are less mobile and may be bedridden, exacerbating the possibility of constipation. Fecal impaction is often common in this patient population and inspection for such must be undertaken. In addition, this population tends to abuse laxatives more than the general population.

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Evaluation of Constipation

In a patient presenting with complaints of constipation, one must first exclude irritable bowel syndrome. With such, further questioning must be directed at excluding other associated disease states as causing physiologic constipation. A review of the patients medical history is a must, as is a review of all prescribed and over the counter medication use. Questions should be directed as to whether this is new in onset or present since birth. If present since birth, this may suggest a congenital cause of constipation versus a new physiologic or idiopathic process. Questions about bleeding per rectum or pain with defection should be asked since may suggest a structural or mucosal process. In addition, abdominal pain and bloating in association with constipation is additionally important to differentiate true idiopathic constipation from irritable bowel syndrome.

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Physical Examination

Physical examination should be directed at excluding systemic disease causes of constipation. These include a detailed neurologic examination to include pinprick of the perianal area (anal wink) and digital exam to access rectal tone. A close inspection of the anorectal region should be undertaken along with digital examination to exclude the presence of pain, which would suggest anal fissure.

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Diagnostic Studies

Barium enema may help in delineating patients with megacolon and Hirschsprung disease. Flexible sigmoidoscopy may be helpful in detecting lower colonic neoplasms and obstructive lesions versus evidence of chronic laxative abuse that can be characteristically noted by mucosal changes with a black discoloration known as melanosis coli.

Colonic transit studies may be helpful in patients with severe constipation to exclude those with normal colonic transit. Classically, the use of radiopaque markers, which are ingested, in patients with a high-fiber diet have abdominal x-rays performed on two to three day intervals. The majority of normal patients will have passage of these markers within 70 hours of oral consumption. Presence of makers beyond 3 days may suggest colonic inertia. Anorectal manometry is the technique of measuring anal sphincter tone with a manometry catheter placed into the anus. This study may have value in differentiating patients with Hirschsprung disease and other neurologic defect. Defecography is a technique in which barium is instilled into the rectum and, under fluoroscopy, evacuation is observed by a trained expert. Defecography may have value in patients with complaints of excessive straining during defecation; however, its utility is limited to technical and interpretive expertise.

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Diagnostic Workup

The majority of patients who present with complaints of constipation need not have a significant diagnostic workup. Once irritable bowel syndrome and systemic causes such as diabetes, hypothyroidism and neurologic causes have been excluded, attempts at manipulations of the diet may be all that is needed to be attempted. In patients though with severe constipation, in which simple dietary measures have not had significant improvement, there may be value in further diagnostic workup. In patients who fail conventional pharmacotherapy, a colonic transit study with radiolucent markers may have value, differentiating those patients with true colonic inertia and those with normal colonic movement. In patients with normal studies, this may serve as a reassurance to both the patient and the physician. Unfortunately, in patients with true colonic inertia as demonstrated by delayed transit by radiolucent markers, dietary manipulations have poor response. These patients probably should undergo anorectal manometry to exclude sensory motor causes and imaging of their colon with barium enema and flexible sigmoidoscopy .

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Treatment for Constipation

Dietary manipulations are the first order in treating patients with chronic constipation. In general, I first recommend increasing fiber content, between 20 to 30 grams of dietary fiber per day. The use of fiber and its effect of improving symptoms of constipation has less to do with water retention and more to do with mechanical factors such as the bulking effects of fiber with respect to colonic microbial ecology and the interaction with intraluminal content. Fiber contents in food content varies greatly. In patients with severe idiopathic constipation behavioral approaches may have benefit. This practice is often attempted in children with idiopathic constipation. Behavioral modification is centered at achieving regular evacuations on a scheduled basis in an attempt to eliminate the accumulation and buildup of stool.

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Pharmacological Therapy

Unfortunately, the majority of patients will self-medicate themselves by the utilization of over-the-counter laxatives. Prior to the initiation of pharmacological intervention, the clinician must insure that fecal impaction not be present, and if present, cleared. Once cleared, enemas may have a role in this setting. I usually recommend starting with either saline or phosphate (Fleet) enemas, though phosphate enemas should be avoided in patients with renal disease. Mineral oil enemas may have a role in more difficult patients, and Soapsuds enemas should be avoided. Laxatives can be considered in more chronic patients. Laxatives are essentially divided into five major categories, including bulk forming laxatives such as fiber, emollient laxatives, hyperosmolar laxatives, saline laxatives and stimulant laxatives (click to see Table 3)

Stimulant laxatives are of the most concern for the clinician, since over long-term use they can render the patient dependent on their use, both physiologically and psychologically. Such stimulant laxatives include phenolphthalein and bisacodyl based laxatives and anthraquinones(e.g., Dulcolax, Ex-Lax). The anthraquinone laxatives increase fluid electrolyte accumulation in the distal ileum and colon through unknown actions. Phenolphthalein laxatives are stored primarily in the small intestine and undergo an intrahepatic circulation, which may explain their long duration of action. These directly stimulate colonic motor physiology and inhibit glucose and sodium absorption of the colon to increase intraluminal fluid content. In general I avoid using this class of laxatives.

Bulk forming laxatives are comprised of mostly natural polysaccharides, synthetic polysaccharides or cellulose derivatives. For their maximum effect, increased water is recommended. Hence, these are somewhat contraindicated in patients on fluid restriction diets. These agents come in a variety of forms as either a powder (Metamucil), biscuit (Metamucil), tablet (Fibercon). In addition, some tube feeding preparation may have added fiber. These agents are generally safe and well tolerated with minor side effects of bloating and flatulence reported, but with continued use, most of these complaints will pass. Care should be taken not to use these agents in patients with bowel strictures or obstructions.

Emollient laxatives consist primarily of mineral oil and docusate salts . Mineral oil may decrease absorption of fat-soluble vitamins A, D and K. Mineral oil should be administered between meals, and avoided in patients at risk for aspiration, since it can cause potential fatal lipid pneumonia. Docusate salts (Colace) lower the surface tension of stool, which subsequently allows the mixing of aqueous and fatty substances, which softens stool and permits easier defecation. In addition docusate salts stimulate fluid and electrolyte secretion

Hyperosmolar agents include electrolyte solution containing polyethylene glycol ( GoLYTELY) and non-absorbable sugars such as lactulose and sorbitol. In general these agents are well tolerated, but may have side effects of bloating and flatulence. These agents can be used on a chronic basis.

Saline laxatives ( e.g., milk of magnesia, citrate of magnesia) contain non-absorbable cations and anions that exert an osmotic effect to increase intraluminal water content. These agents should not be used in patients with renal disease or congestive heart failure, and should be avoided for chronic use.

Prokinetic agents such as erythromycin, cisapride (Propulsid) and metaclopramide (Reglan) have been used to some extent in helping patients with chronic constipation. None are FDA approved for constipation, and cisapride was recently taken off the US market.

In general, I start with fiber, and if not successful, will the proceed to either a lavage solution or hyperosmolar agent. I avoid stimulant and saline catharctics. In some patients in whom pharmacotherapy and dietary intervention have little success, alternative treatment may include biofeedback training, and in the most severe forms of symptomatic idiopathic constipation surgery may be contemplated. Surgery can only be contemplated after a thorough workup has excluded other causes of constipation.

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Table I.

Diseases Associated with Constipation
Neurologic causes	Central neurologic causes	Metabolic and endocrine disorders	Collagen vascular muscle disorders
Hirschsprung disease Chagas’ disease Intestinal pseudo obstruction Autonomic neuropathy Neurofibromatosis	Multiple sclerosis Spinal cord lesions Parkinson’s disease Trauma to Nervi erigentes Cerebrovascular disease	Diabetes mellitus Hypothyroidism Hypercalcemia Hypocalcemia Pregnancy Panhypopituitarism	Systemic sclerosis Amyloidosis Dermatomyositis Myotonic dystrophy