Constipation

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[edit] Constipation

Charles Telfer Williams

Constipation is difficult to define. A strictly quantitative measure can be used, such as the number of bowel movements, but reports of perceived constipation (including straining, painful bowel movements, or sense of incomplete evacuation) have little relation to the number of bowel movements. For this reason a better definition of constipation is a perceived change in bowel habits, which leads to more difficult or less frequent bowel movements. Using a self-report of constipation, the incidence of disease is 12.8%.^[1] Clinically this self-report is the most useful definition, since it more accurately reflects patient's presenting symptoms.

General factors contributing to constipation are mechanical blockage, relative dehydration of the colonic feces, decreased intestinal transit time, and suppression of the natural urge to defecate. Many of these factors relate to diet (fluid and fiber intake) and physical activity. Mechanical blockages can be purely obstructive, can contribute to decreased transit time, or can lead to suppression of defecation in painful conditions such as hemorrhoids. The hydration of the colonic contents is crucial to the passage of stool by ensuring lubrication, bulk, and consistency of the stool. Decreased intestinal transit time leads to increased time for water absorption in the colon and thus relative dehydration of the fecal matter. Similarly, suppression of the natural defecation urge leads to increased colonic time; if habitual, it can cause rectal distention and megacolon, which may damage the nerves and muscles, leading to decreased colonic motility. The interrelation of these factors is complex, making the treatment of chronic constipation a challenge.

[edit] History.

The history is the key to the correct diagnosis and treatment of the vast majority of patients with constipation. Differentiating between chronic and acute constipation is a useful first step. Acute constipation may be defined as a persistent change in bowel habits for less than 3 months. Acute constipation is often caused by a change in only one of the general factors that lead to constipation and is therefore often easier to treat. Chronic constipation is change in bowel habits longer than 3 months, is more frequent as people age, and tends to result from a more complex interplay of the general factors that lead to constipation. Defining what was “normal” for the patient and what has changed is important. Quantifying the number of bowel movements, consistency (loose, soft, normal, hard, rocklike), pattern, and volume can be useful, especially for tracking improvement after starting treatment. It is important to assess fluid and fiber intake and physical activity levels and note any changes that might be associated with the constipation.The age of the patient is relevant; not only does the incidence of constipation increase with age,^[2] but the etiology of constipation in older patients is more frequently multifactorial as well.^[3] Young patients are more likely to have a single, common problem (e.g., irritable bowel syndrome, pregnancy) or an unusual etiology (e.g., Hirschsprung's disease).

Associated symptoms of distention or bloating, abdominal pain, anorexia, hematochezia, painful movements, tenesmus, straining, urgency, and presence of flatus or grease can help clarify the etiology. Obtaining evidence of other medical conditions contributing to constipation, including a past medical history or current symptoms of hypothyroidism, scleroderma, CREST syndrome, and other diseases associated with autonomic neuropathies (e.g., diabetes mellitus), is necessary. Psychiatric assessment for depression and other mental disorders can be helpful.

Finally, the physician should assess the patient's efforts at self-treatment. Chronic laxative use may lead to distention of the bowels and actually exacerbate constipation.

[edit] Physical Examination.

The examination should be aimed at confirming or disproving possible causes raised by the history. Hydration status should be assessed by evaluation of the oral mucosa, skin turgor, tears, and color or specific gravity of the urine. Examination of the thyroid should be done on all patients to rule out enlargement or nodules. An abdominal examination evaluates for surgical scars, distention, masses (stool or other), and tenderness. An anorectal examination looks for fissures, hemorrhoids, strictures, masses, rectal prolapse, prostatic hypertrophy, stool consistency, and size and muscle tone of the rectum. A guaiac test for occult blood is controversial, since a vigorous rectal examination can cause bleeding. Anal fissures can result from constipation as well as perpetuate it because of painful defecation and suppression of the evacuative urge. Hemorrhoids can block normal defecation, or their pain can lead to suppression of the normal urge. Anorectal strictures can be a mechanical barrier to normal bowel movements. In female patients, bimanual examination of the pelvic organs can rule out masses or enlarged organs not palpable by abdominal examination. The patient should strain to allow an adequate assessment for rectal prolapse or rectocele. A general neurologic examination assesses for spinal cord injuries, spina bifida occulta, cerebral palsy, multiple sclerosis, Parkinson's disease, and specifically, perianal sensation and rectal tone.

[edit] Alarm Symptoms.

Although serious illnesses (e.g., carcinoma) as causes of constipation are rare, several alarm symptoms may trigger an expedited evaluation: (1) persons over 40 (due to the increasing incidence of colorectal carcinoma), (2) unexplained constipation of recent onset, (3) worsening constipation with abdominal pain accompanied by blood or mucus, (4) progressively decreasing number of bowel movements, (5) symptoms of obstipation (acute constipation, nausea, vomiting, abdominal pain and distention, inability to defecate, hard stool in rectum), (6) rectal bleeding, and (7) unexplained weight loss.^[4] In the absence of acute severe signs, a symptomatic approach to the evaluation and treatment may be justified initially, even without a clearly identified diagnosis. Most constipation will respond to this approach, and if it does not, further evaluation is warranted.

[edit] Medications.

Drugs are one of the most common causes of constipation. Functional intestinal hydration is decreased by cholestyramine and diuretics, leading to harder stools and difficult passage. Intestinal motility is decreased by medications with anticholinergic properties, including anti-Parkinson's agents (benztropine, trihexyphenidyl, biperiden, ethopropazine), tricyclic antidepressants, monoamine oxygenase inhibitors, and neuroleptics. Other medications often associated with constipation are iron preparations, aluminum, opiates, phenytoin, sympathomimetics (cold medications), calcium channel blockers, and oral contraceptives.

[edit] Medical Conditions.

Medical illnesses can lead to constipation. Irritable bowel syndrome is probably the most common of these, affecting an estimated 17% of the population,^[5] and can vary in presentation from intermittent diarrhea to constipation and often a combination of the two (see Chapter 110 ). Psychiatric illness, particularly new depression, is often associated with constipation. Even with a quantitative measure of bowel movements in the normal range, persons with psychiatric illnesses are five times more likely to report constipation.^[6] These patients should be reoriented as to what constitutes “normal” Uncontrolled diabetes can lead to dehydration and enteropathy, which leads to decreased transit time. Hyperparathyroidism and other causes of hypercalcemia may similarly be associated with dehydration and constipation. Constipation is seen in more than 50% of patients with hypothyroidism.

[edit] Empiric Therapy.

After assessment, consideration of treatment begins. Since life-threatening pathology as yet undetected is relatively uncommon, an empiric trial of lifestyle modification is usually a safe and productive course. Empiric therapy is also indicated when patients are taking essential medications that tend to constipate or if an underlying disease causing constipation is not fully treatable. The usual empiric trial includes increasing three elements: fluids, fiber, and activity (FFA), because the lack of these three is associated with constipation.^[1] Generally, consumption of 2 to 3 L of liquid a day or a 30% increase above the current level should be adequate. Two simple ways to aid compliance are to have the patient fill a 2-L soda bottle with water or to drink enough water so that the urine is clear (not yellow). Decreasing caffeine may also be useful in improving hydration. Stool hydration can also be improved by the use of nonabsorbable sugars; naturally occurring sorbitol is found at high levels in fruits (e.g., apples, prunes, their juice forms). Dietary fiber may be increased through food (fruits, vegetables, whole grains, beans) or fiber additives (e.g., psyllium, bran). A high-fiber diet of 20 to 30 gm a day is recommended.^[7] Increased activity for most patients involves changing habits rather than inability. Walking 30 minutes a day for at least 5 days a week is a good start. Activities that promote inactivity (e.g., TV watching) should be limited. A 2-to 4-week trial of these changes should result in some improvement.

If FFA are insufficient to improve constipation, it may be necessary to initiate stooling with enemas or suppositories with or without the judicious use of cathartics. In general, however, these should be avoided.

[edit] Reassessment.

If a trial of FFA does not produce the desired effect, it is necessary to assess the patient's compliance and the physician's diagnostic certainty. If the diagnostic certainty is high and patient compliance was poor, it is reasonable to give another trial of FFA while trying to improve compliance. If compliance was good or diagnostic certainty is low, the physician should consider further workup.

[edit] Laboratory Studies.

The next step is to rule out underlying diseases by blood tests: calcium, glucose, thyroid-stimulating hormone (TSH), and lead, since hypercalcemia, hyperglycemia, hypothyroidism, and lead toxicity can all cause constipation. If an abnormality is found, efforts should be directed to clarify the cause and treat the underlying illness. If no abnormality is found, the physician should strongly consider proceeding to further diagnostic tests before returning to empiric therapy.

[edit] Further Workup.

Abdominal radiography is a relatively inexpensive test and may reveal some causes of constipation. If an abnormality is found, further workup is indicated. If the abdominal radiograph is normal, the physician should proceed with further evaluation, which could include flexible sigmoidoscopy and barium enema. Obtaining stool for fecal occult blood is inexpensive and should be done. Colonoscopy could substitute for flexible sigmoidoscopy and barium enema in some patients, especially those with symptoms suggestive of carcinoma or with a strong family history. If the patient recently immigrated from or traveled to lesser developed regions, evaluation of stool for ova and parasites may be warranted. Intestinal motility studies can also be done in treatment-resistant cases with a normal workup. Biofeedback may be helpful in patients with decreased intestinal motility.

[edit] REFERENCES