Hepatic Lipidosis in a Cat
History. You are asked to examine a 3-year-old intact female cat. She apparently had been normal, even fat and happy, until 2 weeks ago, when she disappeared from her owner’s apartment for 4 days.
When she returned, the cat seemed depressed and would not eat. Over the next few days she became progressively more listless, almost somnolent.Clinical and Laboratory Examination. The cat has a normal pulse, temperature, and respiratory rate, but she is depressed and responds little to handling. The ocular sclerae (whites of the eyes) appear icteric, or jaundiced. The latter physical sign leads you to suspect liver disease, so you submit blood samples for biochemical analysis. Analysis of blood taken from Ihe jugular vein reveals a higher-than-normal concentration of bile acids and bilirubin, confirming a diagnosis of liver disease. A needle-aspiration biopsy of the liver reveals hepatocytes that are distended with large droplets of nonstaining material, probably fat.
Comment. The presence of significant concentrations of bile acids in blood, other than in the hepatic-portal circulation, is evidence of reduced liver function. Recall that bile acids are absorbed from the ileum into the portal vein, in which they return to the liver. The normal liver extracts bile acids from portal blood efficiently, allowing only small amounts to escape into the systemic circulation; thus, elevated concentrations of bile acids in jugular blood indicate liver disease.
Hepatic lipidosis, or "fatty liver,” is a common disease of cats, initiated by a period of stress combined with either an unwillingness to eat or a lack of available food. In either situation the cat begins to mobilize large quantities of fat to support metabolic energy needs. Normally, much of the mobilized NEFA would be expected to be taken up by the liver and converted to VLDL for export to energy-using tissues.
In cats that experience fatty liver, the hepatic influx of NEFA appears to overwhelm the liver’s capacity to synthesize and secrete VLDL, so fat accumulates in the liver. When the fat accumulation becomes severe, hepatic function is compromised, and the cat becomes systemically ill. Appetite becomes severely depressed, leading to a downward spiral of events in which the hepatic lipidosis becomes more and more severe.Treatment. Treatment consists of reversing the state of negative energy balance by force-feeding. Various methods of force-feeding exist; the most practical approach is placement of an indwelling gastric tube. The lube is often passed through the nostrils but may be placed by a number of different techniques, including direct intubation through the wall of the abdomen. The latter technique is facilitated by the use of a fiberoptic gastroscope. Once the cat is in positive energy balance, adipose mobilization ceases, and the liver eventually clears of fat. Tube feeding may need to continue for several days before the cat begins to eat on its own. Tube feeding has greatly improved the prognosis for hepatic lipidosis, although it is still a life-threatening condition.