Causes of hydronephrosis in dogs and cats

Purpose: Hydronephrosis represents a comparatively rare disease of the kidneys in dogs and cats. In this study patients of the clinic for small animals with proven hydronephrosis are evaluated and causes of hydronephrosis are compared. Materials and methods: The patient data between 2005 and 2015 from the clinic for small animals were evaluated. In this study we included those animals that had at least one kidney being altered in terms of hydronephrosis. The underlying cause had to be confirmed either by a pathological examination or by surgery. Additionally, all those cases were included in which the underlying cause could not be identified during surgery. Those animals, which were diagnosed with hydronephrosis based on ultrasound examination, but which did not undergo any further investigations, were excluded. Results: In this study 29 animals from the examination period were finally included, comprising six cats and 23 dogs. In four animals a bilateral hydronephrosis could be diagnosed, ten animals showed a right-sided hydronephrosis, 15 animals had a left-sided hydronephrosis. In 15 animals neoplasia was responsible for hydronephrosis including seven transitional cell carcinomas. Furthermore we found an ectopic ureter in five animals and a ureteral calculus in four animals. Conclusions: There are different causes for hydronephrosis in dogs and cats; in young animals an ectopic ureter should always be considered whereas in older animals a neoplastic disorder is most likely.