Assessment of different bioptic and immunohistochemical techniques for the diagnosis of feline infectious peritonitis (FIP)

The only conclusive test to diagnose Feline Infectious Peritonitis (FIP) is represented by the histological analysis of affected organs, eventually supported by the immunohistochemical detection of Feline Coronavirus (FCoV) antigen within the lesions. The aim of this study was to evaluate the diagnostic efficiency of non-invasive techniques, such as fine needle aspiration biopsies (FNAB) and tru-cut biopsies (TCB) on liver and kidney, the organs most frequently affected during this disease, and to check the usefulness of immunohistochemistry and immunocytochemistry for FCoV antigen on these samples. The study was performed on 25 cats naturally infected by FCoV, sampled during necropsy or just before euthanasia. We obtained good results from hepatic TCBs, while the renal ones were often inadequate or without evident lesions. Viral antigen was detectable on the majority of the traditional biopsies but rarely on TCBs from both liver and kidney. FNABs were often non-diagnostic or non.consistent with FIP. In some cases FNAB was consistent with FIP while the correspondent TCB it was not and vice versa. Immunocytochemistry often showed disappointing results. Results of this study suggest that non invasive bioptic techniques can provide diagnostic information mainly on liver and that it should be advisable to use both the techniques