Canine Chronic Hepatitis

Copper-associated hepatopathy is a leading cause of chronic hepatitis in dogs, increasing in prevalence since 1997 when copper supplements in commercial dog foods were modified to a more bioavailable form. Retrospective evaluation of liver biopsies from Labrador Retrievers and Doberman Pinschers from 1980 to 2013 indicated that dogs of these breeds, with and without chronic hepatitis, had significantly higher hepatic copper concentrations in the last 10 yr of the study. Management of body copper homeostasis relies on numerous copper transporters, chaperones, and binding proteins, as well as biliary canalicular egress. Copper-associated hepatopathy is best characterized in Bedlington Terriers, which have a mutation (deletion of exon 2) of the COMMD1 copper transporter protein. Careful breeding programs guided by liver biopsy and genetic testing (PCR gene mutation test) have remarkably reduced disease frequency in Bedlington Terriers. However, some Bedlington Terriers with biopsy-confirmed copper-associated hepatopathy lack this specific gene mutation.

Failure to excrete copper into bile leads to chronic hepatitis and, eventually, cirrhosis and liver failure. Affected dogs develop high liver copper concentrations by 1 yr of age (normal: <400 mcg/g dry liver or 400 ppm), which progressively increase during the first 6 yr of life (values may be > 12,000 ppm). Liver injury is reflected by increased ALT activity and has been shown in dogs with hepatic copper as low as 600 ppm.

Three disease phases were historically characterized in Bedlington Terriers. Acute hepatic necrosis occurred in dogs <6 yr old, presenting with hepatomegaly, vomiting, lethargy, anorexia, jaundice, copper-induced hemolytic anemia, and hemoglobinuria. Copper-associated hemolytic anemia occurs only with massive hepatic necrosis, which releases large amounts of copper into the systemic circulation. Death usually occurs within 48–72 hr of onset of clinical signs. In this group of dogs, untreated survivors suffered recurrent bouts of critical illness induced by stress (eg, whelping, attending dog shows, traveling). Another clinical presentation involves chronic hepatitis associated with clinical features, including chronic weight loss, HE, ascites, and jaundice. Some dogs develop an acquired Fanconi syndrome (glucosuria, aminoaciduria, metabolic acidosis, inappropriately alkaline urine pH), signaling renal tubular copper toxicity. The last clinical presentation was recognized in young, clinically healthy dogs, simply demonstrating increased ALT activity and increased hepatic copper concentrations (on liver biopsy). This presentation progresses to acute hepatic necrosis or chronic hepatitis. Rarely, an affected dog remained asymptomatic until another disease process caused liver injury augmented by excessive hepatic copper stores.

Genetic testing is recommended for selection of Bedlington Terrier breeding stock. However, definitive diagnosis of copper-associated hepatopathy requires liver biopsy in adult dogs with qualitative copper stains reconciled with quantitative copper measurements.

Many other purebred and mixed-breed dogs of all ages also may develop copper-associated hepatopathy. More commonly and perhaps more severely affected are Labrador Retrievers; whether the high breed popularity influences this observation remains unclear. Doberman Pinschers, West Highland White Terriers, and some dogs related to Dalmatians also may develop profoundly increased hepatic copper concentrations accompanied by severe liver injury. A genetic cause has not been identified in any of these breeds. It is important to emphasize that copper-associated hepatopathy can be the primary cause of hepatitis in any dog (purebred or mixed breed) and can be definitively diagnosed only by liver biopsy. There is no recognized gender predisposition.

Histologic features of copper-associated hepatopathy include a focus on the centrilobular region (zone 3), finding eosinophilic granules within the cytosolic compartment of hepatocytes and within macrophages in areas of single cell necrosis. Small granulomas develop subsequent to hepatocyte necrosis and release of copper granules into the surrounding parenchyma. Zone 3 lesional–associated parenchymal collapse is verified with reticulin staining (centrilobular collapse) and fibrillar collagen deposition with Masson trichrome staining (centrilobular connective tissue deposition). With advanced injury, regenerative nodules and regions of parenchymal extinction are seen. The prominent role of copper in driving tissue injury is verified by finding copper granules (rhodanine staining) in nearly every hepatocyte within regenerative nodules.

Treatment of copper-associated hepatopathy requires copper chelation with concurrent restriction of copper intake from dietary and water sources. Dietary copper restriction can be achieved by feeding a prescription diet formulated for dogs with HE (delivering 2.2–2.5 g of protein/kg body wt). These low-protein formulas can be supplemented with protein sources low in copper to raise the dietary protein intake to 3.5 g of protein/kg body wt. Supplementary protein sources are selected using the USDA food tables (sort based on copper concentration), with feeding amounts of selected foods calculated using the Nutritional Analysis Tool 2.0 (http://archive.myfoodrecord.com/ human nutrition). Copper in water should contain <0.1 ppm (0.1 mcg copper/L); if copper pipes transport water, flushing the system for 5 min will eliminate any leached copper.

Administration of antioxidants is important, because copper induces liver damage through oxidative injury. Chelation therapy with d-penicillamine (15 mg/kg, PO, bid, given 30 min before feeding, for ≥4-–6 mo) is the gold standard treatment. Thereafter, chronic therapy may be instituted by reducing the d-penicillamine dosage by half and administering the drug every other day while maintaining dietary copper restriction. Alternatively, the dog may be treated with zinc acetate (see below). Concurrent administration of pyridoxine (25 mg/day) is advised during d-penicillamine treatment, because this drug has antipyridoxine (vitamin B₆) effects. If d-penicillamine chelation is not tolerated, trientene hydrochloride can be used (5–7 mg/kg, PO, bid, given 30 min before feeding). Caution is warranted with trientine used at the originally higher recommended dose, because this has induced acute renal failure in dogs with severe copper storage hepatopathy.

An alternative approach to manage copper storage hepatopathy is daily administration of oral zinc (acetate, gluconate, sulfate) to inhibit copper uptake from the GI tract (zinc induces enterocyte metallotheinine, which irreversibly binds copper and prohibits its absorption; copper is subsequently eliminated with effete enterocytes in feces). Although zinc treatment theoretically increases dietary options, study of the efficacy of zinc treatment in people with Wilson disease confirms unreliable control of dietary copper uptake. Zinc therapy must not be given concurrent with chelation therapy, because this will thwart efficacy of each treatment. Oral zinc is not well tolerated by some dogs, commonly causing vomiting, nausea, and inappetence. If zinc therapy seems more suitable for chronic treatment in a specific dog, a loading phase of elemental zinc at 5–10 mg/kg/day is given in two divided doses, 30 min before meals. Plasma zinc concentrations are monitored to ensure that circulating zinc is not nearing toxic values (>800 ppm). After several months, the dosage can be reduced to 2–3 mg/kg/day divided bid, but without study of radiolabelled copper uptake the efficacy of treatment in an individual dog remains unknown.

Vitamin E (10 IU/kg/day, PO) and biologically available SAMe (20 mg/kg/day, PO, on an empty stomach) are recommended antioxidants that also have anti-inflammatory and potentially antifibrotic effects. Vitamin C is contraindicated in copper storage hepatopathy, because it may foster injurious transition metal effects.

After chelation therapy, it is essential to continue to limit copper ingestion in food and water lifelong. Adherence to a copper-restricted diet and water source may obviate the need for continual chelation or zinc therapy.

Idiopathic chronic hepatitis is defined as chronic necroinflammatory self-perpetuating liver disease associated with a nonsuppurative inflammatory infiltrate. To qualify as an idiopathic syndrome, an underlying cause should have been rigorously pursued yet not discovered. Autoimmune hepatitis is included in this classification. An antinuclear antibody test, testing for endemic infectious diseases (titer or antigen tests), and investigation of drug and toxin exposure, along with dietary, environmental, and family history, must be undertaken. Middle-aged to older adult dogs are more commonly affected; there are no breed or gender predilections.

Clinical features include variable anorexia or hyporexia, lethargy, weakness, vomiting, diarrhea, weight loss, jaundice, PU/PD, and in severe or advanced disease, coagulopathies, ascites, and HE. Earliest laboratory findings are persistent or cyclic increases in activity of ALT, AST, ALP, and GGT. With advancing disease, increased TSBA concentrations are followed by hyperbilirubinemia. Other findings may include a nonregenerative anemia, leukocytosis, and hyperglobulinemia. In late-stage disease, portal hypertension causes development of APSSs and the associated laboratory markers of RBC microcytosis, hypocholesterolemia, hypoalbuminemia, prolonged APTT and/or PT, and ammonium biurate crystalluria. At this stage, overt signs of HE may manifest. In early disease, liver size is normal and there may be no demonstrable ultrasonographic lesions. In late-stage disease, radiographs may demonstrate a small liver with nodular lesions detected on ultrasound examination. Ultrasonographic evaluations also may disclose ascites and APSSs in dogs with advanced liver injury.

Definitive diagnosis requires liver biopsy to detail acinal distribution of liver injury, the type of inflammatory infiltrates, the presence of lobular remodeling and fibrosis, and accumulation of copper and/or iron. Chronic, sustained, unexplained increases in liver enzymes usually indicate liver biopsy. Biopsy specimens should be submitted for both aerobic and anaerobic bacterial cultures and quantification of copper, iron, and zinc. Copper stains must be reconciled with quantitative copper measurements to avoid erroneous interpretations. Liver biopsies must be large enough to detail at least 15 contiguous portal triads, and biopsies must be taken from several different liver lobes. Samples collected only from apparent “mass lesions” can lead to erroneous diagnoses. Application of special stains will disclose the acinar location of liver injury (reticulin staining); presence of collagen deposition of fibrosis (Masson's trichrome staining); extent of iron accumulation in macrophages, Kupffer cells, and hepatocytes (Prussian blue staining); and the extent and location of hepatocellular copper accumulation (rhodanine staining).

Supportive care (nutritional, vitamin supplementation) and use of specific therapies to slow inflammation and fibroplasia and to restore liver antioxidant status are recommended. Antibiotics are initially prescribed empirically until results of the biopsy and tissue cultures become available, and then adjusted or discontinued based on culture results. Additional treatments include ursodeoxycholic acid as a hepatoprotectant and anti-inflammatory choleretic (15–20 mg/kg, PO, divided bid, given with food), polyunsaturated phosphatidylcholine as an antifibrotic (PhosChol^® [the specific source used containing 52% of the active antifibrotic component dilinoleoylphosphatidylcholine] 25–50 mg/kg/day, given PO with food), vitamin E as an antifibrotic and antioxidant (10 IU/kg/day, given with food), and bioavailable SAMe as an antioxidant (20–40 mg/kg/day, PO, on an empty stomach).

Immunosuppressive drugs are used only after careful consideration and exclusion of infectious or toxic causes and when an active disease process (nonsuppurative or pyogranulomatous inflammation) is characterized on liver biopsy. Prednisolone or prednisone is usually started at a dosage of 2–4 mg/kg/day, for 7–10 days and titrated downward to a maintenance level of 0.5–1 mg/kg, given every 24 hr or on alternate days, depending on patient response. In the presence of ascites or APSSs, dexamethasone is used instead of prednisone or prednisolone, because it is a synthetic glucocorticoid lacking mineralocorticoid effects. The dose is adjusted considering its longer biologic half-life (72–96 hrs) and higher potency (7–10 fold more than prednisolone or prednisone) such that dexamethasone is used at 0.1–0.2 mg/kg, PO, given every 3 days after a daily loading dose for 3 days. An immunomodulatory agent additional to the glucocorticoid is used to enable titration of the glucocorticoid dosage to the lowest effective dose. This reduces the dose of each immunosuppressive drug, reducing their adverse effects and achieving a multimodal immunosuppressive effect. Adverse effects of glucocorticoids in chronic hepatobiliary disease include sodium and water retention (which can exacerbate or promote ascites), catabolic effects (which can promote HE), GI ulceration and enteric bleeding (which can precipitate HE), pancreatitis, predisposition to secondary infections, glucose intolerance, and iatrogenic hyperadrenocorticism (glycogen-like VH).

Azathioprine is most commonly used at a dosage of 1–2 mg/kg/day for 3–5 days, then every other day. Beneficial effects may not be seen for up to 8 wk. Because azathioprine can cause bone marrow suppression and gastroenteric, pancreatic, and rarely liver toxicity, frequent follow-up assessments are imperative. If azathioprine causes acute bone marrow suppression (within 1 mo), treatment is discontinued until recovery, then restarted with a 25%–50% reduction in dosage. If bone marrow toxicity is identified only after chronic administration (months), azathioprine should be permanently discontinued. Pancreatitis and idiopathic hepatotoxicity are rare adverse effects that also mandate drug discontinuation. Mycophenolate mofetil is used in dogs that cannot tolerate azathioprine or, alternatively, as an initial immunosuppressant. Recommended dosing is 10–20 mg/kg, PO, bid for 7–10 days, then every 24 hr, followed by dosage titration based on patient response. Cyclosporin is another alternative immunosuppressant used in combination therapy. Some dogs previously managed well on azathioprine have lost remission on conversion to cyclosporin. Other dogs started on cyclosporin as their primary immunosuppressant have responded well. In the absence of placebo-controlled clinical trials for treatment of canine immune-mediated hepatitis, treatment is individualized to each dog based on sequential monitoring and, sometimes, follow-up liver biopsy. Discontinuation of immunosuppressive therapy is not recommended in dogs with chronic hepatitis; if drugs are discontinued, they should be withdrawn gradually, with close monitoring (serum biochemical profiles).

Because complete remission is difficult to evaluate clinically, a follow-up biopsy may be required. In most cases, serum ALT activity serves as a surrogate marker of disease activity. Prognosis is widely variable. Some dogs live ≥5 yr after initial diagnosis. Dogs with ascites require dietary sodium restriction and treatment with furosemide and spironolactone (see Portal Hypertension and Ascites in Small Animals). Dogs with HE require dietary protein modification and may benefit from lactulose and administration of low-dose metronidazole.

If immune-mediated hepatitis is considered the definitive diagnosis, careful consideration should be given before administration of routine vaccinations. Nonspecific immune stimulation may adversely stimulate hepatitis and cause disease flare.