Ultrasonogram of the duodenum. Ultrasonogram of the cranial part of the duodenum of a cow with obstruction of the duodenum by a rubber calf feeding nipple. The duodenum is severely dilated and has a diameter of 8 cm. 1 Abdominal wall, 2 Duodenum, Dotted line Diameter of the duodenum, Ds Dorsal, Vt Ventral.