Normative Canine Liver Ultrasonography: Papillary Process and Ligamentum Venosum Fissure.

Canine congenital intrahepatic portosystemic shunts originate from the right or left portal branch and are either intralobar or interlobar. A patent ductus venosus (PDV) is an interlobar shunt that arises from the left portal branch and traverses the ligamentum venosum fissure (LVF) between the left lateral liver lobe and the papillary process of the caudate liver lobe. Identifying the LVF may aid in PDV diagnosis during ultrasonography. In this prospective exploratory study, the ultrasonographic appearances of the LVF and adjacent structures were described in 24 dogs without hepatobiliary disease. Four intercostal acoustic windows were used, two on each side of the dog, and detectability of the following structures was recorded: aorta, left portal branch, caudal vena cava, papillary process, LVF, left lateral hepatic lobe, and ligamentum venosum. All structures were found in each dog from at least one window, with varying frequencies of detection per window. At least one window provided dynamic observation of the left lateral liver lobe, LVF, papillary process, and caudal vena cava aligned left to right, craniodorsal to and parallel with the long axis of the left portal branch. Probe placement on the left hypochondriac region (left dorsal to the xiphoid process) provided the best window, followed by the right hypochondriac region. More dorsal windows (costal regions) were less useful, especially on the left. The LVF was visible in all dogs (100%) from the left hypochondriac window and in 19 dogs (79%) from the right hypochondriac window, justifying further investigation in dogs with intrahepatic portosystemic shunts.