Manometry is used to measure the pressures in the esophagus. These test are useful in patients with difficulty swallowing, repeated heartburn and regurgitation. The measurement of pressure in the rectum and anus is useful in patients with constipation and incontinence. 24-hour pH study is useful in heartburn and regurgitation that is not responding to medications. Colon transit study is helpful in patients with constipation which is not responsive to routine laxatives.