I never checked for any gastric residual volume in 4 years nor was I instructed to do so, not while hospitalized at any time or by visiting nurse, unless while unconscious or in ICU. Seems to be many unknowns, done by medical providers, and is new to me. I was only on the pump for several months while hospitalized in 2010, which it may or may not be used for.
http://lifeinthefastlane.com/education/ccc/gastric-residual-volume/