The Collaborative International Dictionary of English v.0.48:

Gastroscopy \Gas*tros"co*py\, n. (Med.)
   Examination of the abdomen or stomach, as with the
   gastroscope.
   [1913 Webster]

WordNet (r) 3.0 (2006):

gastroscopy
    n 1: visual examination of the stomach by means of a gastroscope
         inserted through the esophagus