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Constipation is the most common digestive complaint in the United States. Gut motility is affected by diet, activity level, anatomic lesions, neurologic conditions, medications, toxins, hormones, rheumatologic conditions, infection, and psychiatric conditions.

Constipation is demonstrated by the presence of hard stools that are difficult to pass. Several historical features may be helpful in eliciting the cause, including new medications or dietary supplements, a decrease in fluid or fiber intake, or a change in activity level. Acute onset implies obstruction until proven otherwise. Associated symptoms, such as vomiting, abdominal distention, and inability to pass flatus further suggest obstruction. A history of unexplained weight loss, rectal bleeding, or unexplained iron-deficiency anemia suggests colon cancer. A family history of colon cancer would escalate one's suspicion. Associated illnesses can help disclose the underlying diagnosis: cold intolerance (hypothyroidism), diverticulitis (inflammatory stricture), or nephrolithiasis (hyperparathyroidism). Diarrhea alone does not rule out constipation/obstruction, as liquid stool can pass around an obstructive source.

Physical examination should focus on detection of hernias or abdominal masses. Bowel sounds will be decreased in the setting of slow gut transit, but increased in the setting of obstruction. Rectal examination will detect masses, foreign bodies, hemorrhoids, abscesses, fecal impaction, anal fissures, or fecal blood. The latter, accompanied by weight loss or decreasing stool caliber, may confirm the presence of colon cancer. Fecal impaction itself can cause rectal bleeding from stercoral ulcers. The presence of ascites in postmenopausal women raises suspicion of ovarian or uterine carcinoma.

The differential diagnosis for constipation is extensive, as noted in Table 38-1. Directed testing in acute constipation, based on level of suspicion, can include a complete blood count (to rule out anemia), thyroid panel (to rule out hypothyroidism), and electrolyte determinations (to rule out hypokalemia or hypercalcemia). Flat and erect abdominal films may be useful in confirming obstruction or assessing stool burden. CT scan of the abdomen and pelvis with IV and PO contrast may be necessary to identify bowel obstruction or other organic causes of constipation.

Table 38-1 Differential Diagnosis of Constipation

Chronic constipation is usually a functional disorder that can be worked up on an outpatient basis. However, complications of chronic constipation, such as fecal impaction and intestinal pseudoobstruction, will require either manual, colonoscopic, or surgical intervention.

Treatment of functional constipation is directed at symptomatic ...

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