Early diagnosis of familial nephropathy in English cocker spaniels.

Two litters of English cocker spaniels (ECSs) produced by familial nephropathy (FN) carriers were evaluated to characterize the early features of this disease. Three puppies developed FN. Proteinuria, which began when these puppies were five-to-eight months old, was the first abnormality detected. Proteinuria persisted while each puppy's growth rate slowed, and renal function gradually deteriorated. The interval from onset of proteinuria to development of azotemia was two-to-nine months. Characteristic glomerular capillary basement membrane (GCBM) lesions were seen with transmission electron microscopy (TEM) of renal biopsy specimens obtained during this interval. Ultrastructural GCBM lesions progressed substantially during the interval from biopsy to necropsy. However, routine light microscopic findings did not allow definitive diagnosis of FN in either biopsy or necropsy specimens. Detection of FN can be accomplished by screening at-risk ECSs for proteinuria. Renal biopsies are required to confirm the diagnosis in dogs for which proteinuria cannot be explained otherwise. Percutaneous needle biopsy specimens sufficient for TEM must be used to examine the GCBM to make a definitive diagnosis.