Page 748 - Clinical Small Animal Internal Medicine

716 Section 7 Diseases of the Liver, Gallbladder, and Bile Ducts

History and Clinical Signs an ammonium chloride solution per rectum (ammonia
VetBooks.ir Patients with portal vascular abnormalities may be clini- tolerance test). Ammonia is labile in serum, and the
ammonia tolerance test is somewhat more invasive and
cally asymptomatic (abnormality detected after routine
wellness screening, or preanesthetic blood testing), display can be very dangerous, and thus serum bile acids are pre-
ferred over ammonia as a clinical screening test.
vague and self‐limiting clinical signs, or present with Hematologic abnormalities include anemia with microcy-
severe neurologic abnormalities associated with HE. tosis and often a mature neutrophilia.
Common clinical signs include a picky appetite or pica,
failure to thrive, hypersialism (most evident in cats), spo-
radic vomiting, polyuria and polydipsia, urinary irrita- Confirmation of Portosystemic Shunting
tion and obstruction caused by ammonium biurate This is most easily done using nuclear scintigraphy; imag-
calculi, episodes of abnormal mentation accompanied by ing the patient following rectal or transsplenic administra-
ataxia, and amauratic (apparent) blindness. Cats with tion of technetium pertechnetate. Contrast portography,
CPSS may have copper‐colored irises, although this is following injection of radiographic contrast agent through
not always the case, and it is not pathognomonic . a catheter placed in the jejunal vein or percutaneously by
Dogs with CPSS sometimes present with a history of
generalized motor seizures, although in a subset of cases means of splenic injection ( splenoportography), provides
another mechanism for confirmation that portal blood is
the seizures are caused by a co‐morbidity such as idio- passing directly into the caudal vena cava and bypassing
pathic epilepsy or granulomatous meningoencephalitis the liver. Contrast portography also provides a mecha-
(more recently referred to as meningoencephalitis of nism for determining the anatomy of the portosystemic
unknown etiology), rather than the shunt itself (see shunt, if a good‐ quality study is achieved. Chapter 61 pro-
Prognosis section). Behavior changes including aggres- vides further details on the methods to image the animal
sion may occasionally prompt presentation. Dogs with with a portosystemic shunt.
CPSS may have other intermittent problems that seem to
result from systemic debility, such as coughing, ocular
discharge, and urinary tract infection. Imaging of the Portal Vasculature
Ascites is very uncommonly seen in dogs with CPSS
unless they have been on a restricted protein diet for an Abdominal sonography is the least expensive and inva-
sive modality, but confidently finding a portosystemic
extended period of time. Ascites is more common in shunt can be difficult in very small dogs, dogs with intes-
cases of portal hypertension accompanying end‐stage tinal gas or ingesta, or with shunts that are in unusual
liver disease or portal venous hypertension/dysplasia.
locations. Even in the hands of an experienced sonogra-
pher, shunts may not be located in up to 25% of patients.
Even when the vessel is not identified, circumstantial
Diagnosis evidence for CPSS may include turbulence within the
prehepatic caudal vena cava, renomegaly, microhepatica,
There are a number of diagnostic methods, including and urinary calculi.
demonstration of liver dysfunction, confirmation of por- Three‐dimensional imaging using computed tomogra-
tosystemic shunting, imaging of the shunt, and histologic phy (CT) or magnetic resonance imaging (MRI) is
evaluation of the liver. becoming the “gold standard” of diagnosis. Dual‐phase
CT angiography (DPCTA) allows confirmation of
portosystemic shunting, clarification of the exact shunt
Clinical Pathology
anatomy, identification of other congenital abnormali-
Biochemical abnormalities typically include low to low‐ ties, calculation of liver volume, assessment of hepatic
normal BUN, cholesterol, albumin, glucose and protein C, perfusion in both the arterial and venous phase, and
and elevated liver enzymes (alanine aminotransferase[ALT], identification of urinary calculi. DPCTA is essential for
alkaline phosphatase[ALP]). Serum bile acid activity is planning transvenous coil embolization.
measured before (resting) and after eating (post prandial),
to gauge the degree to which bile acids leak into the sys- Differentiating CPS from PVH‐MVD
temic circulation from the portal vein, rather than being
extracted by enterohepatic circulation. Serum bile acid Dogs with these two conditions may present in exactly
activity should be elevated in animals with portosystemic the same way, although dogs with PVH‐MVD are less
shunts, and the post prandial sample is more frequently likely to demonstrate overt signs of HE. Confirmation by
abnormal than the resting sample. Plasma ammonia levels nuclear scintigraphy, or advanced imaging, that there is
can also be measured before and after administration of no macroscopic shunt, and identification of the histologic