Approach to the Patient with Constipation

James M. Richter

Constipation affects 15% of adults in Western and industrialized societies and ranks among the most frequent reasons for self-medication, particularly in the elderly. For patients, there is no uniform definition of constipation, but to most, it means movements that are too infrequent, stools that are too hard, and incomplete or difficult evacuation. Consensus criteria help to identify those with functional etiologies (Table 65-1). Bowel habits vary widely among normal people, and perceptions of what constitutes normal function are diverse. Population studies show that most people have more than three bowel movements per week, with men likely to have at least five.

The primary physician must be able to detect any underlying pathology and provide symptomatic relief and reassurance to those with functional etiologies. The prevalence of excessive laxative use and inadequate dietary fiber intake make it imperative that the physician be knowledgeable about the actions and adverse effects of available laxative preparations in addition to dietary alternatives to their use.

PATHOPHYSIOLOGY AND CLINICAL PRESENTATION (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 and 15)

The process of elimination of fecal waste requires two processes: enteric transit and rectal evacuation of stool. Constipation may arise secondary to interference with either of these processes.

Impaired Colonic Transport

Colonic transport can be impaired by inadequate dietary fiber, metabolic factors, mechanical obstruction, motor disorders, drugs, psychiatric conditions, and neurologic disease.

TABLE 65-1 Rome Diagnostic Criteria for Functional Constipation

1. Must include two or more of the following:
	a. Straining during at least 25% of defecations
	b. Lumpy or hard stools in at least 25% of defecations
	c. Sensation of incomplete evacuation for at least 25% of
	defecations
	d. Sensation of anorectal obstruction/blockage for at least 25%
	of defecations
	e. Manuel maneuvers to facilitate at least 25% of defecations
	f. Fewer that three defecations per week
2. Loose stools are rarely present without the use of laxatives.
3. There are insufficient criteria for irritable bowel syndrome.
Criteria should be fulfilled for the last 3 months with symptom onset at least 6 months prior to the diagnosis. Locke GR, Pemberton JH, Phillips SF. AGA Technical review on constipation. From Gastroenterology 2000;119:1766.

Inadequate Dietary Fiber

The transit time that it takes for food to reach the anus is partially a function of the amount of fiber in the diet. Normal people placed on a diet containing 15 g of bran fiber per day have twice the number of movements per week as those on an uncontrolled or low-fiber diet. Patients with constipation solely on the basis of low dietary fiber usually have intermittent complaints that fully resolve with alteration of diet alone.

Inactivity

Exercise has an important positive effect on the propulsion of bowel contents. Colonic transit is significantly greater in physically active people than in those who get little exercise. Previously active persons often become constipated when confined to bed due to illness. Less dramatic, but probably no less important, is the effect of a sedentary lifestyle; constipation is common in inactive people.

Metabolic and Endocrine Disturbances

Metabolic and endocrine disturbances can slow colonic transport. Hypokalemia, hypercalcemia, hypothyroidism, and diabetes are the most important of these in terms of frequency or potential reversibility. Hypokalemia can produce a generalized ileus and is most often seen in patients who take diuretics. When constipation is caused by hypothyroidism, other manifestations of the disease are usually present, although sluggish bowel movements may be the presenting complaint. Constipation is a bothersome problem in some patients with diabetes; 20% of those with neuropathy report severe difficulty. Significant hypercalcemia (serum calcium level >12 mg/100 mL) can slow bowel motility.

Mechanical Obstruction

Mechanical obstruction from tumor, stricture, or volvulus may be responsible for the new onset of constipation. Cramping abdominal pain and distention in conjunction with a marked change in bowel habits are characteristic. Many patients with colorectal cancer report constipation, which is often a symptom of advanced disease. Constipation may be a presentation of Crohn disease because transmural involvement predisposes to scarring and obstruction (see Chapter 73).

Motor Dysfunction

Constipation is the most frequent symptom of irritable bowel syndrome, a common motility disorder of unknown etiology (see Chapter 74). Patients complain of chronic abdominal discomfort related to alterations in bowel habits and relieved by defecation. They report irregular bowel movements, often diarrhea alternating with constipation (although one may predominate). Passage of mucus, a sense of incomplete evacuation, and bloating or distention add to the clinical picture.

Drug Use

Drug use may precipitate constipation. Opiates and agents with anticholinergic activity such as antidepressants are frequently implicated. Calcium-channel blockers may slow down bowel motility, and cholestyramine may induce constipation by binding bile salts. Aluminum hydroxide and calcium carbonate antacids are constipating. The habitual use of laxatives is associated with impaired motor activity. The typical clinical picture is a long history of chronic constipation or a desire to feel “well cleaned out,” followed by increasing laxative dependence, decreasing response, and, ultimately, a sluggish, poorly contracting bowel. The question of whether a prior underlying motor disorder or actual damage from laxative use is the cause remains unsettled.

Psychiatric Disease and Psychosocial Distress

Psychiatric disease and psychosocial distress can play important roles. An underlying depression is often contributory, and bowel complaints may be one of many somatic symptoms (see Chapter 227). Patients with irritable bowel syndrome have an increased prevalence of somatization, anxiety, and phobias. Disturbances in bowel motility and visceral perception have been documented. Constipation develops in the presence of an excessive degree of nonpropulsive contractions and segmentation of bowel contents. At other times, excessive propulsive activity is noted, typically after meals, resulting in diarrhea.

Neurologic Impairment

Constipation may be a presenting symptom of neurologic disease. Spinal cord injury that leads to compression of the cauda equina can slow bowel motility and also cause urinary retention and incontinence. Multiple sclerosis may compromise bowel function, as can ganglionic abnormalities. In most instances, other neurologic deficits are present. Disease limited to loss of neurons in the bowel wall typically presents as chronic, refractory constipation; it may date from childhood or, as noted previously, be associated with long-standing laxative use. A permanently damaged neuromotor apparatus may also occur as a consequence of scleroderma.

Impaired Evacuation

Among the mechanisms of compromised evacuation are inhibition of the normal defecation reflex, dehydration, and pelvic floor dysfunction.

Inhibition of the Rectal Defecation Reflex

Inhibition of the rectal defecation reflex has been documented in cases of painful local anal pathology, neurologic disease (e.g., Parkinson disease, multiple sclerosis), long-term use of laxatives, and voluntary suppression. Patients with this problem are found to have stool packed into the rectal ampulla. Voluntary suppression of the urge to defecate may be a concomitant of a hectic daily pace or traveling. The resulting intermittent constipation may lead to excessive use of laxatives and enemas and damage to the reflex emptying mechanism.

Pelvic Floor Dysfunction

Pelvic floor dysfunction accounts for some cases of intractable constipation of unknown etiology. It may be a consequence of inadequate relaxation or inappropriate contraction of the puborectalis and anal sphincter muscles, pelvic floor dyssynergy, or both. Patients complain of the need to strain despite a strong urge to defecate. They may also report a persistent uncomfortable sense of rectal fullness and the need to remove stool digitally from the rectum to obtain relief. With pelvic floor dyssynergy, patients find that supporting the perineum helps during a bowel movement.

Other Purported Mechanisms

Inadequate fluid intake is commonly believed to play a role, but confirmatory evidence is lacking. Water is known to be an effective means of distending the stomach, which can stimulate intestinal activity.

DIFFERENTIAL DIAGNOSIS (4,8,12,16,17)

The causes of constipation can be grouped according to pathophysiology: impaired motility, rectal dyssynergy neurologic disorders, obstruction, and local anorectal pathology (Table 65-2). Many cases remain undiagnosed after initial assessment but respond to empiric therapy. Slow colonic transit and pelvic floor dysfunction often play etiologic roles in such cases, especially in middle-aged and older women with chronic intractable constipation.

WORKUP (4,6,8,10,16,17)

History

Evaluation begins with a definition of the size, character, and frequency of bowel movements, followed by a determination of the chronicity of the problem. Acute constipation is more often associated with organic disease than is a long-standing problem. Chronic complaints that wax and wane for months and years point to a functional disturbance, perhaps compounded by habitual laxative use. The patient must be asked about symptoms that suggest an underlying significant gastrointestinal disease, such as abdominal pain, nausea, cramping, vomiting, weight loss, melena, rectal bleeding, rectal pain, and fever. Anorexia, bloating, belching, flatus, mucus in the stool, headache, depression, and anxiety should also be recorded; these symptoms may be associated with constipation of any etiology but often accompany functional disorders.

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