Evaluation of Rhodanine-stained Liver Cytology to Diagnose and Monitor Copper-associated Chronic Hepatitis in Dogs

Background: Rhodanine-stained liver cytology can detect hepatic copper using a minimally invasive technique and could help diagnose and monitor dogs with Copper-Associated Chronic Hepatitis (CAH).

Objectives: Evaluate the utility of cytologic copper to 1) differentiate CAH from Immune-mediated Chronic Hepatitis (ICH) and 2) monitor treatment response in CAH dogs.Animals: Fourteen client-owned dogs with CAH treated with D-penicillamine and a copper-restricted diet for 6 months and 17 dogs with ICH.

Methods: Dogs with CAH and ICH were prospectively enrolled based on histologic criteria and copper quantification. Liver cytology was graded semi-quantitatively (1-9) via rhodanine-staining at diagnosis for both ICH and CAH and 1, 3, and 6 months into treatment of CAH. A Spearman’s correlation was evaluated between cytologic copper grade and quantitative hepatic copper. A Wilcoxon-rank sum test compared cytologic copper between dogs with CAH and ICH at diagnosis and pre- and post-treatment in dogs with CAH.

Results: Median (Q1-Q3) hepatic copper (µg/g dw) was higher at diagnosis in CAH [2825 (2073-3225)] compared to ICH [295 (24-690)] (p=0.0001) and cytologic copper grade was higher in CAH [7 (4-7.25)] compared to ICH [4 (3.5-6)] (p=0.01). Cytologic copper grade correlated with quantitative hepatic copper in all dogs (p< 0.0001, rho=0.78). In CAH dogs, hepatic copper (p<0.001) and cytologic copper grade (p<0.001) reduced following 6 months of chelation and dietary treatment. Conclusions and Clinical Importance: Cytologic copper could help assess dogs with CAH and ICH, but there was overlap between groups and correlation with quantitative copper was moderate.