Feline esophagus appears when the esophagus contracts longitudinally and the term arises from its supposed similarity to the appearance of cat esophageal motion (although why barium studies were being performed in cats is still a mystery). The appearance has also been termed "esophageal shiver", which may be a better name since it implies that the esophagus is reacting to a semi-noxious stimulus. Thanks to Liz Chorney, MD for capturing this at just the right moment.
The main importance of recognizing this sign is twofold:
so as not to mistake it for something more serious, e.g.
linear scarring (fixed "stepladder" scarring) in chronic reflux esophagitis