BACKGROUND: Many of the ultrasonographic abdominal findings of adult cattle probably also apply to calves. However, significant changes associated with ruminal growth and transition from a milk to a roughage diet occur in young calves during the first few months, and it can be expected that ultrasonographic features of organs adjacent to the rumen such as spleen and liver also undergo significant changes. These have not been investigated to date and therefore the goal of this study was to describe ultrasonographic findings of the spleen, liver, gallbladder, caudal vena cava and portal vein in six healthy calves from birth to 104 days of age. Standing calves were examined ultrasonographically six times at three-week intervals starting on the first or second day of life using a 5.0-MHz transducer and techniques described previously. RESULTS: The spleen was imaged on the left at the 5th to 12th intercostal spaces. The dorsal and ventral visible limits ran from cranioventral to caudodorsal because of superimposition of the lungs. The size of the spleen was largest at the 7th and 8th intercostal spaces and the maximum thickness was measured at the 9th to 12th intercostal spaces. The liver was seen in all calves on the right and could be imaged at the 5th to 12th intercostal spaces and the area caudal to the last rib. Similar to the spleen, the dorsal visible margin of the liver ran parallel to the ventral border of the lungs. The visible size of the liver was largest at the 8th to 11th intercostal spaces and the maximum thickness was measured at the 8th and 9th intercostal spaces. The parenchymal pattern consisted of numerous fine echoes homogeneously distributed over the entire organ. The gallbladder was most commonly seen at the 9th intercostal space and was circular, oval or pear-shaped on ultrasonograms. It extended beyond the ventral border of the liver depending on the amount of bile. The caudal vena cava was triangular in cross section but sometimes had a round or oval profile and was always seen in at least one intercostal space. The maximum circumference was measured at the 10th and 11th intercostal spaces. The portal vein was circular or oval in cross section and was characterised by stellate ramifications branching into the liver parenchyma. The portal vein could always be imaged at the 7th to 11th intercostal spaces and its mean diameter at the 9th to 11th intercostal spaces ranged from 1.2 cm to 1.8 cm. CONCLUSIONS: The ultrasonographic findings of the spleen, liver, gallbladder, caudal vena cava and portal vein in six healthy Holstein-Friesian calves from birth to 104 days of age serve as reference values for the examination of these anatomical structures in diseased calves.