Calodium hepaticum is a parasitic nematode found primarily in rodents but known to infect numerous other mammal species, and causing in humans the hepatic calodiasis. Herein, we present the first finding of C. hepaticum in Rattus norvegicus in Poland. In this study, we have used the combined pepsin-HCl digestion and molecular techniques to detect C. hepaticum infection in the liver. The results confirm the usefulness of molecular approaches for investigating the biology and epidemiology of C. hepaticum. Additionally in this study, the parts of the small subunit rRNA (18S rRNA) gene of Aonchotheca annulosa from bank vole, Aonchotheca erinacei and Eucoleus sp. from hedgehog were amplified, yielding the first 18S rRNA gene sequences of these Capillariinae nematodes.