Functional nausea and vomiting.

Although functional vomiting (FV), cyclic vomiting syndrome (CVS) and chronic idiopathic nausea (CIN) are fairly rare disorders, it has been increasingly recognized that these conditions can be highly disabling. Traditionally, FV, CVS and CIN have been under-investigated; however, interest in the cause and treatment of these disorders has increased, particularly with regard to their pathophysiology and the evaluation of new treatment approaches. This article presents a literature-based review of the nomenclature, pathophysiology, clinical presentation and management of CIN, CVS and FV. There is a dearth of randomized, controlled trials of treatments for these disorders, owing mainly to their low prevalence. Consequently, referral centers that see a large number of patients with these challenging disorders are working together to share their experience, so that the most productive treatment strategies can be used to help patients. Our knowledge of the treatment of FV, CVS and CIN, as best we know it, is presented here.