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23

Liver
Martha M. Larson

Department of Small Animal Clinical Sciences, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, USA

23.1 Normal Radiographic radiographic signs of generalized hepatomegaly are
Appearance of the Feline Liver rounding or blunting of the caudoventral liver margins
with extension beyond the costal arch (Figure 23.3) [2,3].
The feline liver is located in the cranial aspect of the abdo- The stomach, right kidney, and transverse colon may all be
men, almost completely within the intrathoracic part of displaced caudally.
the abdominal cavity. The convex cranial surface silhou- Several nonpathologic conditions can result in caudal
ettes with the diaphragm, while the more concave caudal extension of hepatic margins, including overexpansion of
border abuts the right kidney, cranial portion of the duode- the thorax or deep inspiration. Older cats can have stretch-
num, and stomach. Abundant falciform fat in cats can ing or elongation of the coronary ligaments attaching the
result in dorsal displacement of the ventral aspect of the liver to the diaphragm, resulting in sagging and caudal
liver on lateral views (Figure 23.1). On ventrodorsal (VD) extension of the liver (Figure 23.4). In addition, neonatal
views, a larger portion of the liver is often right sided. and young cats have a larger liver size compared with
The feline liver is divided into left and right medial and body size, creating the appearance of hepatomegaly with-
lateral lobes, as well as quadrate and caudate lobes. out a true hepatic abnormality [4,5]. Because of the
Individual lobe definition is not possible radiographically. numerous normal variations that can cause hepatic lobe
The gallbladder lies between the two parts of the right extension beyond the costal arch, rounding or blunting of
medial lobe, just to the right of midline (VD view), and in these lobes should also be present before true hepatomeg-
the cranioventral aspect of the liver on lateral projections. aly is considered.
Occasionally, the gallbladder can be seen protruding from There are numerous causes of true generalized hepato-
the ventral aspect of the liver on lateral images [1]. This is megaly in the cat, and radiographic examination alone is
considered a normal variation (Figure 23.2). insufficient to determine the exact etiology. Hepatic con-
Hepatic shape may not be visualized without abundant gestion secondary to elevated pressures in the right heart
surrounding omental and falciform fat. The caudoventral can result in generalized hepatomegaly, with distended
hepatic margin protruding slightly from the costal arch hepatic veins and caudal vena cava noted on alternate
should be relatively sharply marginated, and triangular imaging (ultrasound [US], computed tomography [CT])
in shape. (Figure 23.5). Hepatomegaly is frequently present in cats
with chronic lipidosis (Figure 23.6) [6]. Inflammatory
diseases, including cholangiohepatitis, fungal infiltra-
23.2 Hepatomegaly tion (histoplasmosis), as well as acromegaly can result in
diffuse hepatomegaly [7,8]. Diffuse neoplasia (lym-
Hepatic enlargement can be detected radiographically, phoma, mast cell tumor) can also cause generalized
although mild size changes cannot be assessed accu- hepatomegaly (Figures 23.3 and 23.7). Hepatic ultra-
rately. Both lateral and ventrodorsal abdominal views sound can be used to determine internal architecture and
should be examined to evaluate liver size as hepatomegaly is better suited than radiography for narrowing the list of
may be easily visualized on only one view. The classic differentials.

Feline Diagnostic Imaging, First Edition. Edited by Merrilee Holland and Judith Hudson.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.