(See also Manometry Manometry Manometry is measurement of pressure within various parts of the gastrointestinal tract. Manometry is done by passing a catheter containing solid-state or liquid-filled pressure transducers... read more .)
Impedance planimetry provides real-time assessment of luminal distensibility and geometric changes in response to applied pressure in various parts of the gastrointestinal tract.
A catheter-mounted, balloon-covered probe is placed during a regular endoscopy using sedation and inflated to prespecified pressures. During inflation, pressure sensors along the balloon measure intraluminal pressure and cross-sectional area within a gastrointestinal lumen or sphincter. The measurements are used to calculate a distensibility index (mm2/mm Hg) or compliance of the evaluated area.
The newest generation of probes also produces a realtime graphic display of esophageal contractility patterns.
Impedance planimetry is used in a variety of gastrointestinal conditions, particularly in the esophagus. This technique can be used to evaluate achalasia and can provide useful diagnostic information where high-resolution manometry is nondiagnostic or if the patient cannot tolerate manometry. Recent guidelines recommend its use in the diagnosis and management of achalasia Achalasia Achalasia is a neurogenic esophageal motility disorder characterized by impaired esophageal peristalsis and a lack of lower esophageal sphincter relaxation during swallowing. Symptoms are slowly... read more 
(1 References (See also Manometry.) Impedance planimetry provides real-time assessment of luminal distensibility and geometric changes in response to applied pressure in various parts of the gastrointestinal... read more 
, 2 References (See also Manometry.) Impedance planimetry provides real-time assessment of luminal distensibility and geometric changes in response to applied pressure in various parts of the gastrointestinal... read more ). Additionally, in patients undergoing interventions for achalasia (eg, surgery, peroral endoscopic myotomy), measurement of esophagogastric junction distensibility during and after the intervention accurately measures clinical response to interventions and can help guide therapy.
Another potential use of impedance planimetry is in the diagnosis and management of eosinophilic esophagitis Eosinophilic Esophagitis Eosinophilic esophagitis is a chronic immune-mediated disease of the esophagus resulting in eosinophil-predominant inflammation of the esophagus; it can cause reflux-like symptoms, dysphagia... read more 
. Previous studies have shown decreased esophageal distensibility in patients with eosinophilic esophagitis (3 References (See also Manometry.) Impedance planimetry provides real-time assessment of luminal distensibility and geometric changes in response to applied pressure in various parts of the gastrointestinal... read more ) in whom esophageal fibrosis led to static or minimal changes in cross-sectional area measurements despite increasing balloon pressure and volume. Measurement of esophageal distensibility may show luminal narrowing not seen with conventional endoscopy and is highly suggestive of eosinophilic esophagitis. Further studies are needed to define optimal use of impedance planimetry in this disease.
Impedance planimetry has been studied in the evaluation of gastrointestinal disorders, including gastroesophageal reflux disease (GERD Gastroesophageal Reflux Disease (GERD) Incompetence of the lower esophageal sphincter allows reflux of gastric contents into the esophagus, causing burning pain. Prolonged reflux may lead to esophagitis, stricture, and rarely metaplasia... read more 
) and hiatus hernia Hiatus Hernia Hiatus hernia is a protrusion of the stomach through the diaphragmatic hiatus. Most hernias are asymptomatic, but an increased incidence of acid reflux may lead to symptoms of gastroesophageal... read more 
, and in postsurgical settings, including bariatric surgery Bariatric Surgery Bariatric surgery is the surgical alteration of the stomach, intestine, or both to cause weight loss. In the US, about 250,000 bariatric operations are done in each year. Development of safer... read more and fundoplication. Additional studies have assessed its role in disorders of the gastric pylorus (especially in patients with gastroparesis) and in diseases of the anal sphincter. Its utility and specific role in diagnostic and therapeutics require further study.
References
1. Gyawali CP, Carlson DA, Chen JW, et al: ACG clinical guidelines: Clinical use of esophageal physiologic testing. Am J Gastroenterol 115(9):1412–1428, 2020. doi: 10.14309/ajg.0000000000000734
2. Hirano I, Pandolfino JE, Boeckxstaens GE: Functional lumen imaging probe for the management of esophageal disorders: Expert review from the clinical practice updates committee of the AGA Institute. Clin Gastroenterol Hepatol 15(3):325–334, 2017. doi: 10.1016/j.cgh.2016.10.022
3. Carlson DA, Lin Z, Hirano I, et al: Evaluation of esophageal distensibility in eosinophilic esophagitis: An update and comparison of functional lumen imaging probe analytic methods. Neurogastroenterol Motil 28(12):1844–1853, 2016. doi: 10.1111/nmo.12888
