Impedance testing is a type of test that uses a probe that inflates a balloon inside the esophagus and measures how much pressure it takes to expand it a certain amount. An esophagus that is stiffer or looser than normal may indicate a disorder is present.
Before the test, people do not eat or drink anything for 4 hours.
In this test, doctors pass a thin plastic tube (catheter) through the person's nose down into the esophagus Throat and Esophagus The throat (pharynx) lies behind and below the mouth. When food and fluids leave the mouth, they pass through the throat. Swallowing of food and fluids begins voluntarily and continues automatically... read more (the hollow tube that leads from the throat to the stomach). The tube is covered with a balloon filled with salt water (saline solution). The balloon is used to measure the area across the inside of a part of the digestive tract, such as the esophagus, as well as the pressure inside that part. As the balloon is inflated, sensors along the balloon measure the pressure and diameter of the esophagus. Wires from the sensors transmit findings to a data recorder worn by the person. The pressure measurements and data help doctors further evaluate people who are having problems with their digestive tract, such as trouble swallowing. Impedance testing can also be done to detect any liquid that comes into the esophagus from the stomach, regardless of acidity, so doctors are able to measure both acid (using pH monitors Acid-Related and Reflux-Related Tests Acid-related and reflux-related tests are used mainly to diagnose acid reflux into the esophagus (the hollow tube that leads from the throat to the stomach). Tests may use a monitor on a small... read more ) and non-acid reflux into the esophagus.
Sometimes impedance testing is combined with manometry Manometry Manometry is measurement of pressure within various parts of the digestive tract. People must not eat or drink anything after midnight before the test. In this test, a flexible tube with pressure... read more , another test that measures pressure.
Impedance testing is used to diagnose a variety of gastrointestinal disorders, particularly in the esophagus. For example, this test can be used to evaluate problems with the nerves that control the rhythmic contractions of the esophagus (achalasia Achalasia Achalasia is a disorder in which the rhythmic contractions of the esophagus (called peristalsis) are missing or impaired, the lower esophageal sphincter does not relax normally, and the resting... read more ), evaluate an inflammatory disorder in which the wall of the esophagus becomes filled with large numbers of white blood cells (eosinophilic esophagitis Eosinophilic Esophagitis Eosinophilic esophagitis is an inflammatory disorder in which the wall of the esophagus becomes filled with large numbers of eosinophils, a type of white blood cell. This disorder may be caused... read more ), and possibly evaluate the backward flow of stomach contents into the esophagus (gastroesophageal reflux disease Gastroesophageal Reflux Disease (GERD) In gastroesophageal reflux disease, stomach contents, including acid and bile, flow backward from the stomach into the esophagus, causing inflammation in the esophagus and pain in the bottom... read more 
[GERD]). It can provide doctors with useful diagnostic information if no diagnosis can be made by using manometry or if people cannot tolerate manometry.
Additionally, impedance testing is sometimes done during and after people receive treatment for a digestive disorder. For example, people who are undergoing treatment for achalasia (such as surgery) have the test again because it can determine whether the treatment is working and can help doctors decide what further treatment is needed. The test may also be done in people who have had bariatric surgery Bariatric Surgery Bariatric (weight-loss) surgery alters the stomach, intestine, or both to produce weight loss. In the United States, about 160,000 people have bariatric surgery each year. This number accounts... read more or surgery for reflux Treatment In gastroesophageal reflux disease, stomach contents, including acid and bile, flow backward from the stomach into the esophagus, causing inflammation in the esophagus and pain in the bottom... read more (fundoplication).
Complications of impedance testing are uncommon and include injury to the nose, throat, or the esophagus.
