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.