Absence of bile ducts (BDs) in >50% of portal tracts is currently the most widely accepted criterion for the diagnosis of ductopenia. In this study, we describe an alternative method for the quantitative assessment of BDs based on the percentage of portal tracts containing unpaired hepatic arteries (HAs). Diagnostic criteria for ductopenia were defined as follows: 1. presence of at least 1 unpaired HA in >10% of all portal tracts; 2. at least 2 unpaired HAs present in different portal tracts in a given sample. In liver biopsies from patients with primary biliary cirrhosis and suspected chronic allograft rejection (n=32), loss of BD was detected in 59.4% of patients using the unpaired HA method compared with 43.7% (P=0.31), 21.9% (P=0.005), and 12.5% (P=0.001) by the traditional method, depending onspecific adequacy criteria used (no adequacy criteria, >10 portal tracts, or >5 complete portal tracts per biopsy, respectively). The percentage of portal tracts containing BD(s) was significantly affected by the degree of portal inflammation, fibrosis stage, percentage of complete portal tracts, and biopsy width, whereas none of these factors influenced the prevalence of unpaired arteries. The unpaired HA method showed higher sensitivity for the detection of mild degrees of loss of BD compared with the traditional method, and was not influenced by factors that affected the percentage of portal tracts containing BDs.