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Constipation is the most common digestive complaint in the United States. Gut motility is affected by diet, activity level, and multiple, often overlapping, causes.


Constipation is characterized by the presence of two or more of the following complaints straining, hard stools, incomplete evacuation, and fewer than three bowel movements per week. Constipation is chronic in patients with symptoms for 12 weeks consecutive or nonconsecutive of the preceding 12 months. Differentiating acute from chronic and functional from organic constipation can guide treatment. Functional constipation features include changes in medications or dietary supplements, a decrease in fluid or fiber intake, or a change in activity level including illness or injury. Organic constipation is suggested by acute onset, weight loss, rectal bleeding/melena, nausea/vomiting, inability to pass flatus, fever, rectal pain and change in stool caliber. Organic constipation has priority diagnosis of obstruction and carcinoma. A family history of colon, ovarian or uterine cancer plus an assessment of associated illnesses may elucidate other primary or comorbid diagnoses: cold intolerance (hypothyroidism), diverticulitis (inflammatory stricture), or nephrolithiasis (hyperparathyroidism). Diarrhea may occur with constipation/obstruction symptoms, as liquid stool can pass around an impaction or obstructive source.

Physical examination should focus on detection of hernias, abdominal masses, and ascites (carcinoma). Bowel sounds will be decreased in the setting of slow gut transit, but increased in the setting of obstruction. Visual and digital rectal examination will detect tone, 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 carcinoma. Fecal impaction may produce ulcers causing rectal bleeding.


The differential diagnosis for constipation is extensive, as noted in Table 38-1. Prioritize testing to evaluate organic constipation and complications of functional constipation based on suspicion; this may include a complete blood count (to rule out anemia), thyroid stimulating hormone (to rule out hypothyroidism), and electrolyte determinations (to rule out hypokalemia or hypercalcemia). Flat and erect abdominal films may be useful in confirming obstruction and pseudo-obstruction or assessing stool burden. computed tomography (CT) scan of the abdomen and pelvis with contrast may be necessary to identify organic causes of constipation including obstruction, carcinoma, or impaction.

Table 38-1

Differential Diagnosis of Constipation

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