Introduction
The clinical signs of liver disease (medically referred to as “hepatobiliary disease”) can be extremely variable due to the liver’s extensive interaction with a multitude of other organs and its regenerative capacity. More than half (and maybe up to 70 or 80 percent) of functional liver tissue must be destroyed before liver failure can be diagnosed. There may be no clinical manifestations of liver disease, or the condition may present with a number of nonspecific signs. Once symptoms do develop, liver disease may be advanced, although the severity of any given clinical signs does not necessarily correlate with the extent of liver damage or the animal’s prognosis. Additionally, because the liver is intimately involved in so many bodily functions, what appear to be symptoms of liver disease might actually be caused by an abnormality in another organ or organ system. Keeping this in mind, there are a number of signs that, taking together, can be suggestive of underlying liver dysfunction.
Symptoms of Liver Disease in Dogs
The general, vague and nonspecific signs and physical examination findings often associated with liver disease irrespective of its cause include anorexia/inappetence, depression, lethargy, weakness, weight loss, poor or unkempt haircoat, nausea, vomiting, diarrhea and dehydration. Another sign sometimes seen is abdominal enlargement, which may be the first sign noticed by owners or may be discovered during a routine physical examination by a veterinarian. The distended abdomen is usually caused by an enlarged liver or spleen (“organomegaly,” which means enlarged organ), excess fluid in the space between abdominal organs (called “effusion”), or poor abdominal muscle tone (called “muscular hypotonia”). Each of these causes may or may not be associated with primary liver disease.
Some more specific signs of liver disease include jaundice, bilirubinuria, acholic feces, behavioral and neurological changes and increased frequency of urination and drinking.
Jaundice is the yellow staining of the serum or tissues, including skin and mucous membranes, caused by an excess of the bile pigment, bilirubin. Jaundice, also referred to as “icterus,” can turn a dog’s urine a bright, yellowish-orange color (“bilirubinuria”). Acholic feces – or changes in fecal color – are caused by an absence of bile pigments in the intestinal tract, making the animal’s stools pale, gray and putty-colored. This normally indicates complete bile duct obstruction associated with liver disease.
Behavioral and neurological changes reported to have been seen in dogs suffering from liver disorders include aggression, restlessness, agitation, dementia, disorientation, depression, trembling, circling, ataxia (lack of muscular coordination), staggering, aimless wandering or pacing, head-pressing, blindness, excess salivation, tremors, generalized seizures and even comas. The general term for this condition is “hepatic encephalopathy.” (“Hepatic” means emanating from or pertaining to the liver.) These signs can develop in dogs (and cats) with liver disease because the cerebral cortex of the brain is exposed to intestinal toxins that normally are removed by a healthy liver, but escape hepatic detoxification in cases of liver disease. Most gastrointestinal toxins are derived from bacterial metabolism, or digestion, of proteins and their byproducts. Ammonia is one of the most common GI toxins contributing to the clinical signs of hepatic encephalopathy, which can wax and wane over time. Hepatic encephalopathy is a chronic condition which cannot be cured but can be controlled.
Companion animals with liver disease can also have problems with coagulation, or clotting, of their blood (“coagulopathies”), because of the integral role of the liver in this process. In dogs, the upper gastrointestinal tract – usually the stomach and duodenum, which is the first part of the small intestine - is most commonly affected by coagulation disorders associated with liver disease. This leads to GI bleeding/hemorrhage, which owners may detect by seeing blood in their dogs’ stools. Affected dogs may also vomit blood.
Finally, increased volume of urination and drinking of water can accompany serious liver dysfunction. Your veterinarian may refer to these symptoms as “polyuria” and “polydipsia.”
If your dog exhibits any of the symptoms discussed, and especially if you notice a number of them, please see your veterinarian immediately. Only a veterinarian can run the crucial tests needed to confirm a diagnosis of liver disease.