Constipation or irregularity, is a condition of the digestive system where a person (or animal) experiences hard feces that are difficult to egest; it may be extremely painful, and in severe cases (fecal impaction) lead to symptoms of bowel obstruction. Obstipation refers to severe constipation. Causes of constipation may be dietary, hormonal, anatomical, a side effect of medications, or an illness or disorder. Treatment is with a change in dietary and exercise habits.