Reverse computer tomographic (CT) pattern of vacuolar hepatopathy with fat accumulation in canine and feline liver

Introduction/purpose Different conditions can lead to severe vacuolar hepatopathy with fat accumulation in canine and feline liver. Hepatic lipidosis, in cats, usually results from chronic anorexia and weight loss due to different causes. In dogs, steatosis is generally associated with diabetes mellitus and with hepatocellular vacuolar changes occurring in canine hyperadrenocorticism. The definitive diagnosis is histological, but ultrasonographic or tomographic images may allow a non-invasive description of vacuolar hepatopathy. In human medicine, unenhanced CT is considered the best way to assess fat accumulation within the liver. The aim of the study was to describe an uncommon tomographic pattern of canine and feline vacuolar hepatopathy with fat accumulation. Methods One Labrador retriever and one domestic shorthair cat were referred to our centers after hematology, biochemistry and abdominal ultrasound, for a total body CT due to a suspicion of hyperadrenocorticism syndrome and hepatic disease, respectively. Blood tests revealed an increase of liver enzymes in both animals, albumin/globulin ratio in the cat and blood urea nitrogen, glucose and triglycerides in the dog. Ultrasonography showed an increased liver echogenicity and - in the dog - increase in size of the left adrenal gland. Plain and post-contrast (600 mg/kg i.v. Iodine) total body CT acquisition with soft tissue algorithm was performed. Circular regions of interest (ROI) with an area of 2 cm2 were drawn over the liver avoiding major hepatic and portal vessels. For each ROI, mean (standard deviation, SD) attenuation values (HU, Hounsfield Units) were recorded. Mean (SD) hepatic attenuation values of the two investigated animals were compared to the mean (SD) hepatic attenuation values measured in 10 dogs and 10 cats which underwent CT for unrelated liver diseases, used as control. Fine needle aspiration (FNA) and tissue core biopsy of the liver were also performed in the cat and in the dog, respectively. Results On pre-contrast images, the liver of the dog had a mean (SD) hepatic attenuation value of -18,39 HU (12,78) (Fig. 1), while the liver of the cat had attenuation of -25,04 HU (7,15) (Fig. 2). The average of the mean (SD) hepatic attenuation values in all dogs without hepatic diseases was 63,85 HU (12,03), while it was 55,25 HU (6,77) in the cats with normal liver. Post-contrast CT images revealed a mean (SD) hepatic attenuation value of 30,04 HU (15,7) in the dog and 25,61 (10,48) in the cat. The control animals presented an average of the mean (SD) hepatic attenuation values of 136,28 (15,02) in dogs and 129,25 (9,66) in cats. (Fig. 3). The tomographic diagnosis of lipidosis in the cat and steatosis/hyperadrenocorticism in the dog were confirmed by cytological and histopathological examination, respectively. Discussion/Conclusions Negative hepatic attenuation values with fat storage describe a hypoattenuating reverse CT pattern of the parenchyma, when compared to hepatic vascular structures.