Ultrasonogram of the ventral sac of the rumen. Ultrasonogram of the ventral sac of the rumen of a 27-day-old Swiss Braunvieh calf with ruminal drinking syndrome. The 5.0-MHz linear transducer was held parallel to the ventral midline in the left lower abdominal area. The ruminal content appears heterogeneous and echoic. The undulating line medial to the ruminal wall indicates hyperkeratosis. 1 Ventral abdominal wall, 2 Ruminal wall, 3 Ruminal content, Cr Cranial, Cd Caudal.