Emerging hepatobiliary diseases: know the syndromes - DVM
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Emerging hepatobiliary diseases: know the syndromes


DVM360 MAGAZINE


Breeds commonly associated with MVD include the Maltese, Cairn Terrier and Yorkshire Terrier. Clinical signs at presentation often mimic what is seen with portosystemic shunts (PSS) although are generally more mild. These signs include small size, poor growth and an unthrifty appearance. Other clinical signs may include anorexia, vomiting, diarrhea, polyuria and polydypsia, intermittent fever and drug intolerance. Hepatic encephalopathy may result in part from elevated levels of ammonia, mercaptans, short-chain fatty acids and other neurotoxins. Signs of hepatic encephalopathy may include behavior changes, aggression, ataxia, lethargy, circling, dementia, amaurosis, seizures and coma.

Serum bile acids are elevated, and liver enzymes can be normal or elevated. Histologically, changes are similar to findings in patients with macroscopic shunts; therefore the diagnosis is not always clear from a biopsy sample. Typically, there is decreased portal vein diameter or the absence of a portal vein and proliferation of the arterioles in the portal tracts. Hepatocytes are often atrophied and lobules are diminished in size. Treatment is supportive and symptomatic, primarily aimed at managing hepatic encephalopathy.

Dietary/hydration considerations

It is important to manage fluid, glucose and electrolyte imbalances. Diet should be highly digestible, low in protein content and have high levels of zinc and vitamin E. Lactulose may be indicated to manage encephalopathy; ursodiol (actigall) to reduce hepatic inflammation and/or injury and promote choloresis may also be of benefit. Ursodiol also appears to have beneficial immunomodulatory effects (decrease immunoglobulin and interleukin responses). S-Adenosyl-L-methionine (SAMe) may be of benefit as a precursor to antioxidants in the hepatocyte and is involved in the restoration of glutathione (GSH) levels.

GSH plays an important role in detoxification mechanisms of the cell and depletion can indirectly cause toxic effects by increasing oxidative stress.

If patients continue to exhibit seizure activity, anticonvulsant therapy may be indicated. Long-term prognosis is typically poor if clinical signs are difficult to manage. There are many instances, however, where clinical signs never become apparent in dogs with MVD.

Vacuolar hepatopathy results in alterations of hepatic function as well as structure due to hepatocytes becoming vacuolated or infiltrated with fat, glycogen, edema, amyloid or other metabolic wastes. Cytosolic swelling is seen cytologically or histologically. Determining an underlying etiology in patients with vacuolar hepatopathies can prove difficult or may be more obvious as in patients with known exogenous or elevated endogenous glucocorticoids (steroid hepatopathy). Neoplasia, or other hepatobiliary diseases are commonly found concurrently in patients with vacuolar hepatopathy, possibly supporting the theory that illness-evoked physiologic response could be related to the development of vacuolar changes.

Increases in ALP are seen in cases of steroid hepatopathy. G-ALP (glucocorticoid-associated ALP) is unique to the canine and generally comprises the majority of ALP concentration; however, the diagnostic usefulness of G-ALP is still under debate.

If a patient has evidence of vacuolar hepatopathy and elevated ALP, glucocorticoid use must be ruled out. If there is no history of corticosteroid administration, the patient should be screened for hyperadrenocorticism. Some of these patients also have abnormally high concentrations of sex hormones such as progesterone and 17a-Hydroxy-progesterone.

It has been hypothesized that increases in progestin steroid hormones may result in vacuolar hepatic changes as well. Abnormal progestin levels may be due to adrenal enzyme deficiency, adrenal adenomas, or other unidentifiable adrenal masses. Recent studies are investigating the Scottish Terrier as a breed potentially over-represented for this condition.

Vacuolar hepatopathy often is considered "idiopathic" when steroid use and Cushing's disease are ruled out.

Clinical signs may vary depending on the patient and my range from no signs, to vague signs of lethargy, vomiting, diarrhea or signs of the underlying disease such as polyuria, polydipsia, weight gain and polyphagia with hyperadrenocorticism.

Most patients with idiopathic vacuolar hepatopathy live a normal life without adverse consequences, but further research is needed to better understand this disorder. Several patients have had a response (decreases in ALP) to ketoconazole, lysodren and trilostane administration.

Nodular hyperplasia is an age-related phenomenon, which is commonly seen in dogs greater than 8 years of age. There does not appear to be any breed or sex predilection. The condition is not generally associated with clinical signs, but mild to moderate elevations in ALP (alkaline phosphatase) and ALT (alanine aminotransferase), and may be appreciated. When these nodular changes are seen during ultrasonography or surgery, benign hyperplasia must be considered in addition to malignancy.


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