This study confirms that in dogs with confirmed primary chronic hepatitis, those patients with ascites at the time of diagnosis
will have significantly decreased survival times compared with those without ascites. Although the number of dogs reported
in this study is not large, the difference in survival times between these two groups is large enough that statistical analysis
confirms that the difference is not due to chance alone.
The association between ascites and earlier death makes intuitive sense. The pathophysiologic mechanisms thought to be necessary
for ascites formation include the presence of portal hypertension, an increase in renin-angiotensin-aldosterone system activation,
and hypoalbuminemia; all of these parameters imply advanced disease or a globally diseased liver, and each may independently
result in ascites. However, veterinarians should be aware that some owners of dogs with asymptomatic ascites may have elected
to euthanize rather than wait for diuretics to exert their effects, and inclusion of these dogs in this study may have influenced
the reported results. The mean survival time reported for dogs with ascites was shorter than for human patients with the same
histologic and clinical findings, which raises suspicion of this "euthanasia option effect."
In a recent retrospective review of canine chronic hepatitis of multiple etiologies, the prognostic factors associated with
a significantly decreased survival time were jaundice, presence of an abdominal fluid wave (presumptively due to ascites),
small liver size, enlarged portal lymph nodes, and cirrhosis.2 Half the dogs in that study that had a diagnosis of chronic hepatitis had cirrhosis, an advanced and irreversible stage
of hepatic fibrosis. This observation may likewise have been a compounding factor in the study discussed here; dogs with ascites
likely have a more advanced stage of disease at the time of presentation and, therefore, logically have decreased survival.
Unfortunately, the number of dogs with and without ascites that had cirrhosis (as opposed to just occasional fibrosis) was
not reported in this study.
The association between administration of spironolactone and presence of ascites was not surprising, given that this diuretic
is only prescribed to patients with hepatic disease known to have sufficient fluid accumulation requiring medical intervention.
Spironolactone may help slow or prevent ascites via aldosterone antagonism, which results in reduced sodium and water and
reabsorption in the distal renal tubule. In theory, other classes of drugs that inhibit the renin-angiotensin-aldosterone
system (e.g. angiotensin-converting enzyme inhibitors such as enalapril or benazepril, or angiotensin II receptor antagonists such as losartan)
could also be used to decrease ascites formation. However, aldosterone is also pro-fibrotic, and antagonism with spironolactone
may provide additional benefits other than an immediate reduction in ascites.
A reason for the association between feeding a diet formulated for dogs with liver disease and absence of ascites is not as
clear. It may be that some patients with ascites would not have developed this complication if they had been fed such a diet
earlier in their disease progression. Alternatively, the perceived poorer quality of life of dogs with ascites may have caused
most owners to preferentially feed more savory or familiar diets to their pets. Or it may be that those disease factors that
directly or indirectly cause fibrosis, cirrhosis, or development of ascites are not altered by dietary therapy. Nevertheless,
at this time most veterinary hepatologists suggest that dogs with ascites be fed a sodium-reduced diet.
Raffan E, McCallum A, Scase TJ, et al. Ascites is a negative prognostic indicator in chronic hepatitis in dogs. J Vet Intern Med 2009;23(1):63-66.
The information in "Research Updates" was provided by Erika Meler, DVM, MS, and Barrak Pressler, DVM, PhD, DACVIM, Department
of Veterinary Clinical Sciences, School of Veterinary Medicine, Purdue University, West Lafayette, IN 47907.
1. WSAVA Liver Standardization Group. WSAVA standards for clinical and histopathological diagnosis of canine and feline liver diseases. Philadelphia, Pa: Elsevier; 2006.
2. Poldervaart JH, Favier RP, Penning LC, et al. Primary hepatitis in dogs: a retrospective review (2002-2006). J Vet Intern Med 2009;23(1):72-80.