Page 639 - Small Animal Internal Medicine, 6th Edition

CHAPTER 36 Hepatobiliary Diseases in the Dog 611

of them. Symptomatic therapy for HE, ascites, and GI ulcer- and anecdotally in other breeds. Pillai et al. in 2016 reported
ation (if present) is usually successful (see earlier). It should 30 Boxer dogs with ductal plate malformations, suggesting
VetBooks.ir be noted that glucocorticoid therapy is absolutely contrain- an increased prevalence in this breed. Interestingly, there was
a high prevalence of concurrent congenital hepatic abnor-
dicated in these dogs and is likely to worsen the outcome
because of the associated portal hypertension and high risk
cular abnormalities. Two dogs also had Caroli’s disease.
of GI ulceration. This underlines the importance of liver malities such as atrophy of liver lobes or gallbladder or vas-
biopsy in these dogs, allowing differentiation from chronic Recent work at the University of Cambridge in the UK sug-
hepatitis. gests that Skye Terrier hepatitis may in fact also be a con-
One study of dogs with noncirrhotic portal hypertension genital ductal plate abnormality.
concluded that affected dogs might live as long as 9 years
after diagnosis with appropriate symptomatic therapy (Bunch Clinical Features
et al., 2001). A few dogs were euthanized because of prob- Dogs with congenital hepatic fibrosis usually present at a
lems related to persistent portal hypertension (e.g., duodenal young age, with most being under 1 year of age at presenta-
ulceration). Dogs with MVD tend to have milder clinical tion, but occasionally dogs present as old as 10 years of age.
signs than dogs with congenital PSSs and can be managed Clinical signs are typical of portal hypertension (see earlier)
medically with success over the long term. Affected dogs including ascites, vomiting, and diarrhea, and also in some
seem to live comfortably, in good to excellent condition, for cases melena. Some dogs present with HE.
at least 5 years.
Diagnosis
Congenital Ductal Plate Abnormalities Clinicopathologic abnormalities are very similar to chronic
liver disease. Affected dogs usually have elevated liver
Etiology enzymes but very rarely elevated bilirubin. Bile acids are
Ductal plate abnormalities are congenital diseases of the liver often elevated, associated with development of acquired
causes by abnormalities in development of the ductal plate PSSs. Some dogs have microcytic red cells. Diagnostic
(see later). There are a variety of phenotypes depending on imaging findings are generally indistinguishable from cir-
the stage in embryologic development when the abnormality rhosis: dogs usually have a small hyperechoic liver and free
occurs, and there may be some overlap with portal vein abdominal fluid. Some cases may have other congenital
abnormalities. Traditionally, these conditions were consid- abnormalities such as atresia of the gallbladder or a liver
ered rare in dogs, but with increasing awareness of the condi- lobe, or large liver cysts that would increase the index of
tion, more cases are being identified. The commonest suspicion of ductal plate abnormality. However, confirma-
phenotypes in dogs are Caroli’s disease, where bile ducts are tion of diagnosis requires a liver biopsy. Congenital hepatic
large, and cystic and congenital hepatic fibrosis, where there fibrosis typically appears as abnormal, expanded portal
are multiple small bile ductules and associated fibrosis. The tracts with multiple small bile duct profiles and bands of
latter can be confused with cirrhosis on pathology and hence fibrosis both periportally and extending into the liver. These
potential underdiagnosis. The differentiation is important tracts of fibrosis can sometimes resemble lobular dissecting
because dogs with congenital hepatic fibrosis generally have hepatitis. There may also be areas of fibrosis and multiple
a better prognosis than those with cirrhosis if appropriately small bile ducts underneath the liver capsule, similar to Mey-
treated. enburg complexes reported in humans. Bile ducts typically
The ductal plate is the embryonic precursor of the inter- have cuboidal rather than columnar epithelium. Increased
lobular and intralobular bile ducts. It is a double layer of copper accumulation is common in affected boxers and Skye
embryonic epithelium surrounding the portal veins. Bile Terriers, and is assumed to be secondary to abnormal excre-
duct development involves many signaling molecules, and tion. The disease is often patchy affecting individual liver
abnormalities in this development result in a wide variety of lobes more than others.
presentations in human medicine, with persistence of
embryonic bile ducts and varying amounts of periportal Treatment and Prognosis
fibrosis. The drivers of fibrosis in this context remain incom- Treatment of affected animals is symptomatic because
pletely understood. There are a variety of genetic mutations there is no cure for the congenital abnormality. Nonethe-
involved in humans, many of them autosomal dominant, and less, many dogs have a good long-term prognosis with
affected individuals may have concurrent renal cysts or skel- supportive care; a reported median survival in one study
etal abnormalities. The disease phenotype in the liver in Boxers was 8.8 years in dogs without acquired PSS and
depends on which bile ducts are affected; maturation arrest 7.5 years in dogs with PSS. Anecdotally, Skye Terriers and
of small interlobular bile ducts results in congenital hepatic other breeds can also do well long term. Management is
fibrosis, whereas maturation arrest of medium intrahepatic the same as for dogs with portal hypertension, with symp-
bile ducts results in Caroli’s disease. The genetics of ductal tomatic treatment of ascites with spironolactone and careful
plate anomalies are currently unknown in dogs. The first dietary and other management for HE (see Box 36.6). It is
report of congenital hepatic fibrosis in dogs in the veterinary particularly important that affected dogs are fed sufficient
literature was in 2010 (Brown et al., 2010). Since that time, dietary protein for maintenance because long-term survival
cases have been reported in Boxer dogs and Skye Terriers is anticipated.