**Abstract**

Functional gastrointestinal disorders (FGIDs) are disorders of gut–brain interaction; it is a group of disorders classified by gastrointestinal (GI) symptoms related to any combination of the following: motility disturbance, visceral hypersensitivity, altered mucosal and immune function, altered gut microbiota, altered central nervous system processing. In general, investigations on intestinal motility should be reserved for patients with symptoms correlated to motor alterations that greatly influence the quality of life, nutrition and productivity, as they are justified only if a result can be expected that influences the clinical management of the patient. Esophageal High-resolution manometry (HRM) today permits greater understanding of the function of the esophagogastric junction and the esophageal motility. In the more frequent clinical manifestation, like as Gastroesophageal reflux disease (GERD), despite endoscopy, the pH-impedance is considered the most accurate and detailed method to assess acid/weakly acid or non acid gastroesophageal reflux, to identify the specific phenotypes of reflux disease spectrum. To investigate gastric motor function, the scintigraphic gastric emptying test is the gold standard, but it still has poor uniformity of the protocols, that undermine the quality and usefulness of the test. The current and increasingly widespread alternative to scintigraphic emptying is the breath-test with octanoic acid (OBT) or Spirulina labeled with C13, a test that has the favor of not using radioactive substances and that has shown a high concordance with the scintigraphic test. The intraluminal capsule test is a recent promising tool, that records intraluminal pH, pressure, temperature and post-prandial gastric contractions, and transmits wireless data to a receiver. EGG is a non-invasive technique that measures gastric myoelectric activity- and consequently its function- using skin electrodes placed in the upper abdomen. Gastro-jejunal manometry with multiple pressure sensor catheters located in the antrum, pylorus, duodenum and jejunum is the only clinically available test that allows detailed evaluation of coordinated gastro-duodenumjejunal contraction models. The functional ultrasound, the barostat, the SPECT and resonance methods have provided preliminary data on their application in the study of gastrointestinal motility, but the data are still missing and the methods are not validated.

**Keywords:** functional gastrointestinal disorders, functional tests, manometry, pH-impedance
