Ultrasonogram of the anterior dorsal blind sac. Ultrasonogram of the anterior dorsal blind sac of the rumen of a six-year-old Simmental cow viewed from the sternal region using a 5.0-MHz convex transducer. 1 Ventral abdominal wall, 2 Reticulum, 3 Anterior dorsal blind sac of the rumen, 3 Anterior ventral blind sac of the rumen, Cr Cranial, Cd Caudal.