Renal dysplasia is a developmental anomaly of the kidneys which is considered to be the primary lesion in juvenile progressive nephropathy, a condition leading to chronic renal failure in young dogs. It is defined as disorganised development of the renal parenchyma due to abnormal differentiation, and pathological lesions include persistent foetal structures, dysplastic tubules and cartilaginous and osseus metaplasia. The aetiology of renal dysplasia in dogs is still unknown, but possible causes are infection with canine herpesvirus, teratogenic substances or intrauterine ureteral obstruction. In some breeds renal dysplasia is a familial or inherited disease. Clinical signs of chronic renal failure, such as polyuria, polydipsia, vomiting, weight loss, anorexia, lethargy and anemia, usually appear before the age of 2 years. The purpose of this study was to obtain more knowledge about epidemiology, breed predisposition and morphology of renal dysplasia.
In the epidemiological part of the study the prevalence of renal dyplasia in nine different breeds during the time period 1981-2001 was investigated. In the histopathological part the presence of dysplastic changes in the kidneys was examined in 57 cases of renal dysplasia in Tibetan Spaniel and Flat-coated Retriever. The highest prevalences for the whole time period were noted for Shih Tzu (0,57%), Tibetan Terrier (0,56%), Lhasa Apso(0,48%) and Tibetan Spaniel (0,42%). For the breeds Irish Soft-coated Wheaten Terrier, Cairn Terrier and Flat-coated Retriever the prevalence was a little bit lower (0,29%, 0,26% and 0,20%, respectively) and for English Cocker Spaniel and Cavalier King Charles Spaniel the prevalence was very low (0,09% and 0,08%, respectively). For Shih Tzu and Tibetan Terrier, but not for the other breeds, the prevalence decreased during the latter part of the time period. More than half (64,2 %) of the dogs in this study were < 2 years of age at the time of diagnos/euthanasia, and the highest proportion of dogs < 2 years of age was noted for Cairn Terriers, Tibetan Terriers and Lhasa Apsos (80,0%, 80,0% and 75,0%, respectively). A sex predisposition for renal dysplasia was detected for Flat-coated Retrievers and Cavalier King Charles Spaniels, in which females represented 87,5% and 85,0 %, respectively, of the cases.
In the morphological study, the most commonly detected signs of renal dysplasia were foetal glomeruli, dysplastic tubules and persistent metanephric ducts in both the Tibetan Spaniel and the Flat-coated Retriever. These lesions were found at a frequency of 89%, 22% and 18% in the Tibetan Spaniel and 80%, 53% and 7% in the Flat-coated Retriever, respectively. The observed difference between the two breeds regarding dysplastic tubules was statistically significant (p=0,016). The mean age at the time of diagnosis was 16 months for Tibetan Spaniel and 15 months for Flat-coated Retriever. The morphological changes observed in the Tibetan Spaniel were similar to those reported in the Shih Tzu and Lhasa Apso, whereas the lesions of the Flat-coated Retriever resemble descriptions of familial renal disease in the Soft-coated Wheaten Terrier.
In conclusion, the present study showed that most of the cases of renal dysplasia in the nine breeds examined were diagnosed before the age of two years. The reduced prevalence of renal dysplasia observed for the breeds Shih Tzu and *Tibetan Spaniel for the latter part of the investigated time period suggests that the introduced control programs have been effective. For the ...
