Copper analysis of laparoscopic liver biopsy tissue samples from cats

Hepatic copper accumulation is assessed qualitatively via histopathology, and hepatic copper concentration is measured quantitatively. Laparoscopic biopsy provides samples adequate for histopathology; however, its suitability for copper quantification in cats remains unclear. Liver tissue samples from 19 cats undergoing laparoscopic liver biopsy were evaluated for hepatic copper score and concentration. Copper scores were determined by a board-certified pathologist using rhodanine-stained sections. Hepatic copper concentrations were determined using atomic absorption spectrometry, and the rhodanine-positive pixel ratio was calculated from histological images using ImageJ. Copper-associated hepatopathy was identified in three cats: two with a score of 4 and one with a score of 5. Seven cats demonstrated cholangiohepatitis (scores 0-3). The hepatic copper score was significantly correlated with copper concentration in the 19 cats (Spearman's r=0.757, P<0.001). Rhodanine-positive pixel ratio also correlated with copper concentration (Spearman's r=0.668, P<0.01). Therefore, laparoscopic biopsy provides feline liver tissue feasible for qualitative and quantitative copper analysis. The liver rhodanine-positive pixel ratio offers a useful quantitative alternative when hepatic copper concentration cannot be measured in cats.