Page 621 - Small Animal Internal Medicine, 6th Edition

CHAPTER 36 Hepatobiliary Diseases in the Dog 593

generally avoid them because of the lack of evidence and with confirmed leptospirosis or bartonellosis) because they
potential side effects. are potentially hepatotoxic.
VetBooks.ir Antifibrotics Treatment of portal hypertension
Dogs with chronic hepatitis presenting with clinical signs
The most effective antifibrotic treatment in the context of
chronic hepatitis is to effectively treat the underlying cause.
potentially acquired PSS) have specific management consid-
Fig. 36.4 illustrates the potential for reversal of fibrosis and of portal hypertension (ascites, gut wall congestion, and
even early cirrhosis if the underlying cause is treated. This erations. The treatment of HE associated with acquired PSS
has been well described in human medicine but poorly doc- is the same as the treatment of HE associated with congenital
umented in canine chronic hepatitis. Later in the disease PSS (see later in this chapter).
process, when there is extensive fibrosis, the direct antifi- The treatment of ascites associated with portal hyperten-
brotic agent colchicine can be used. However, the author sion in chronic hepatitis revolves around the use of diuretics,
does not recommend its use as there is no good evidence of first aldosterone antagonists (spironolactone, 1-2 mg/kg PO
efficacy and it has a high incidence of side effects. It is dif- q12h) and then the addition of furosemide (2 mg/kg PO
ficult to believe that colchicine is an effective antifibrotic in q12h) if necessary in refractory cases. The reason spirono-
the liver of dogs given that no effective hepatic antifibrotic lactone is the diuretic of choice in these dogs is due to the
has been identified in humans, in spite of years of research underlying pathophysiology with increase in aldosterone
(Friedman, 2010). Spironolactone may also have some anti- and fluid retention described in Chapter 33. Spironolactone
fibrotic activity. This has been demonstrated in rats with usually takes 2 or 3 days to reach full effect, and the resolu-
chronic hepatitis, so there is an argument to use it. tion of ascites can be monitored by weighing the patient
Antibiotics daily; any acute changes in weight will be caused by fluid
There is a primary indication for the use of antibiotics in shifts. Dietary sodium restriction has also been recom-
dogs with ascending biliary tract infections or suspected mended, although it is unclear how effective or important
bacterial infection as a cause of chronic hepatitis. The latter this is. However, it is certainly wise to refrain from feeding
is rarely proven, but if an atypical leptospiral infection might the patient high-salt snacks and treats.
be present (e.g., if chronic granulomatous hepatitis is seen in It is important to monitor serum electrolyte concentra-
a dog with access to sources of infection, such as rivers or tions, mainly sodium and potassium, daily during the first
ditches), a course of appropriate antibiotics would be wise to few days of treatment and every few weeks to months there-
rule this out. The recommended therapy for leptospiral after, depending on how stable the dog and drug doses are.
infections is to start with intravenous (IV) amoxicillin, Hypokalemia should be avoided because it can precipitate
22 mg/kg q12h, to terminate replication and reduce poten- HE (see later), but it is less likely in a dog on aldosterone
tially fatal liver and kidney complications. If leptospiral antagonists and loop diuretics than in a dog on furosemide
infection is subsequently confirmed by rising titers on serol- alone. Hyponatremia can also occur; if it is marked, the
ogy, dark field microscopy, PCR assay of the urine or blood diuretics should be stopped and the patient given careful
for organisms, or fluorescent in-situ hybridization of live IV replacement until the sodium level is normalized. Thera-
biopsies, this should be followed by doxycycline therapy peutic paracentesis is indicated only for patients with ascites
(5 mg/kg PO q12h, for 2 weeks) once liver function has that is severe enough to compromise breathing. This is
normalized to eliminate the chronic renal carrier state. For actually unusual and is manifested by severe ascites with
additional information on leptospirosis, see Chapter 94. Bar- a tense abdomen and the dog is unable to settle and lie
tonella spp. have occasionally been associated with chronic down. Paracentesis should be accompanied by concurrent
liver disease in dogs, but the optimal treatment for Bartonella IV administration of a colloid plasma expander, plasma,
infection in dogs has not been established. Macrolides (e.g., or albumin; removal of a large volume of fluid contain-
erythromycin) or alternatively fluoroquinolones or doxycy- ing albumin can result in a precipitous hypoalbuminemia
cline have been shown to have some efficacy against some and decrease in oncotic pressure, leading to pulmonary
Bartonella spp. in dogs. It has been suggested that 4 to 6 edema. This is a real problem in dogs with chronic liver
weeks of treatment might be necessary to eliminate infection disease in which the liver’s capacity to manufacture albumin
(see Chapter 94). is reduced.
Antibiotics are also used as part of supportive treatment Dogs with portal hypertension are at risk of GI ulceration
in dogs with HE caused by acquired PSS in end-stage chronic due to splanchnic congestion, as described earlier and in
hepatitis; they are given in a similar way as to dogs with Chapter 33. The clinician must be aware that GI ulceration
congenital PSS to reduce toxin absorption from the gut and may occur acutely in dogs with splanchnic congestion, and
risk of systemic infections (see later). Ampicillin or amoxicil- serious clinical deterioration may occur before melena is
lin is often used long term in these cases, 10 to 20 mg/kg PO apparent because it takes several hours for the blood to pass
q8-12h. from the small to large intestine. Before this occurs, it is
As with other drugs, the clinician should avoid any antibi- possible for the animal to show sudden onset and marked
otics that increase hepatic work or the risk of hepatotoxicity. signs of HE because blood is a high-protein meal in the small
Thus tetracyclines, potentiated sulfonamides, nitrofurantoin, intestine (see earlier) or even for the ulcer to perforate and
and erythromycin should be avoided unless necessary (e.g., cause peritonitis (Fig. 36.5).