Special staining and grading of canine liver cytology samples aids in detection of increased copper content. The prevalence of copper in routine diagnostic liver cytology samples, clinical findings associated with high cytologic copper (cCu) grade, and the correlation between cCu grade and histologic findings, including histologic copper (hCu) grade, are unknown. This data may be helpful in ascertaining when to determine a cCu grade and when interpreting cCu grade.
Clinical data and available archived hepatic histologic and cytologic samples from 198 dogs were collected, evaluated, rhodanine stained, and graded for copper. Prevalence of increased cCu >5 in a randomly collected group of 163 individuals, and the correlation between cCu and clinical data (n = 198), hCu grade (n = 37), or findings on hematoxylin and eosin–stained hepatic sections (n = 32) were evaluated. The observed prevalence was 1.23%. Dogs with elevated alanine transaminase >180 IU/L or aspartate transaminase >90 IU/L and patients who subsequently had hepatic copper quantification were statistically more likely to have pathologic levels of copper detected by cytology. There was significant and modest correlation between cCu and hCu, interface hepatitis, portal inflammation, and fibrosis. Evidence of hepatocellular leakage may be indications for determination of cCu.