Page 922 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Liver disease 897

VetBooks.ir many countries appear free from the disease. Most 5.20
affected horses remain subclinically infected for life
and tolerate the cysts well as they occupy a small vol-
ume of the liver, although occasional cases are seen
where the presence of multiple cysts compromises
hepatic function. *

Clinical presentation *
Horses with bacterial cholangiohepatitis and choleli- *
thiasis tend to present with a combination of pyrexia,
jaundice and colic signs. This is one of the few equine
liver diseases where a diagnosis may be inferred with
reasonable confidence without recourse to histopa-
thology. Tyzzer’s disease is generally first recognised Fig. 5.20 Ultrasonographic image illustrating
as sudden death in foals, although terminal clinical anechoic dilated bile ducts (asterisks) with echogenic
signs such as depression, jaundice, diarrhoea and choleliths (arrows) in a horse showing signs of pyrexia,
neurological signs are sometimes seen. Other forms colic and jaundice.
of infectious hepatitis are not associated with specific
clinical signs, or may frequently be subclinical, and
share features with other causes of hepatic injury and degrees of systemic inflammation, perhaps due to the
insufficiency (see above), depending on the severity loss of the screening function of hepatic Kupffer cells
of disease. Wet ground and a history of infection in that are normally strategically situated between the GI
cattle and sheep locally increases the index of suspi- tract and the systemic circulation. Hepatomegaly and
cion of fascioliasis in horses. Age of the individual bile duct dilatation may be imaged ultrasonographi-
may be a factor in suspecting other parasitic agents cally in bacterial cholangiohepatitis and cholelithiasis
such as nematode infections, tending to be prevalent (Fig. 5.20) and also with some cases of fascioliasis.
in younger horses. CE is primarily seen in horses Serological assays for C. piliforme are available as well
associated with hunting with dogs and such indi- as a faecal polymerase chain reaction assay to support
viduals are generally quite aged due to the declining a clinical diagnosis of Tyzzer’s disease.
practice of feeding horse offal to dogs. Although general ill-thrift is reported in cases of
fascioliasis, pathogenicity may be minor in many cases
Differential diagnosis with clinical impact often mild to negligible and even
Bacterial cholangiohepatitis should be considered serum biochemical markers of hepatic disease may
alongside other causes of abdominal pain in horses, remain within normal limits. Faecal examination
although the coexistence of pyrexia and jaundice are for Fasciola eggs or coproantigen appear to be highly
strong indicators that hepatic infection is indeed insensitive diagnostic methods, a problem that is
the cause. Viral and parasitic causes of liver disease magnified by non-patency of infection in many cases.
share many differential diagnoses as discussed above Serological methods are also described but poor sen-
for other cases of non-infectious liver disease and sitivity also limits their diagnostic usefulness.
hepatic insufficiency. CE in horses is usually suspected on the basis
of characteristic ultrasonographic images showing
Diagnosis spherical (or approximately spherical) 20–70 mm
Systemic inflammatory markers such as neutrophilic diameter anechoic intrahepatic cysts with or with-
leucocytosis and increased acute phase proteins out mobile echogenic sediment within (Fig. 5.21).
including serum amyloid A, fibrinogen, hypoferrae- Single or multiple cysts may be present in the same
mia and hyperglobulinaemia are all consistent with horse and although they are mostly without clini-
infectious hepatitis. However, many non- infectious cal consequence, large burdens have the potential to
hepatopathy cases will also demonstrate varying affect serum hepatic enzymes and/or liver function.