Page 432 - Problem-Based Feline Medicine

424 PART 7 SICK CAT WITH SPECIFIC SIGNS

or storage is suspected. This phenomena is observed
INTRODUCTION
with a variety of non-hepatic primary disorders (e.g.,
renal and gastrointestinal diseases) which may cause
MECHANISM? these cats to later develop primary liver disease. Bile
acid analysis determines hepatic function and the
Jaundice results when serum bilirubin is increased
need to obtain cytologic/biopsy specimens for defini-
above 2 mg/ml.
tive diagnosis.
Most bilirubin originates from senescent erythrocytes
and is processed in the liver for excretion in the bile.
INCREASED BILIRUBIN PRODUCTION
Jaundice results from either increased erythrocyte
(PRE-HEPATIC CAUSES OF JAUNDICE
hemolysis, which exceeds the processing capacity of
OR INCREASE\D LIVER ENZYMES)
the liver, or hepatobiliary disease.
WHERE? MYCOPLASMA HAEMOFELIS
(HEMOBARTONELLA FELIS)*
Pre-hepatic jaundice is due to hemolytic processes.
IMMUNE-MEDIATED ANEMIA
Erythrocyte hemolysis causes release of increased
heme pigments, which overwhelm hepatic process-
ing/excretion of bilirubin. Classical signs
Hepatic jaundice is seen with severe diffuse hepatic ● Pale mucus membranes, PCV usually
cholestasis (via inflammation) or major bile duct < 18%; hemoglobin < 10 g/dl.
obstruction. Inflammation in portal or periportal areas ● Lethargy, in appetence, and anorexia may
causes jaundice early in the disease course; whereas, be observed.
parenchymal injury away from periportal areas results ● +/- fever.
in jaundice development late in the disease course. ● Occasional vomiting.
Post-hepatic jaundice is caused by intraluminal or
See main reference on page 530 for details (The Anemic
extraluminal disorders that mechanically occlude the
Cat).
biliary tree (e.g., gall bladder and common bile duct).
Post-hepatic (extrahepatic biliary obstruction).
Pathogenesis
Rapid destruction of red cells exceeds the liver’s capa-
WHAT?
city to metabolize increased hemoglobin breakdown
Pre-hepatic causes for jaundice are primarily attributable products (bilirubin).
to erythrocyte parasitemia (hemobartellosis), infectious
Most commonly associated with Mycoplasma haemofe-
disease (FeLV), and immune-mediated hemolysis (rare).
lis infection and less commonly with immune-mediated
Hepatic causes for jaundice may be caused by hepatic anemia. Hemolysis may also be caused by feline
lipidosis, cholangiohepatitis syndrome and hepatic leukemia viral (FeLV) infection.
lymphosarcoma.
Pre-hepatic causes for jaundice in the cat are
Post-hepatic causes for jaundice are caused by pancre- uncommon.
atitis and neoplasms involving the gallbladder and bil-
iary tree (less common).
Clinical signs
Non-jaundiced cats with elevated liver enzymes may
Pale mucus membranes, PCV< 18% and often
or may not have significant hepatic disease. An
12–15%; hemoglobin < 10 g/dl.
underlying defect in bilirubin metabolism affecting
conjugation reactions or cytosolic pigment transport Lethargy, inappetance, anorexia.