Ultrasonographic findings of renal dysplasia in cocker spaniels: eight cases

A retrospective study of eight young Cocker Spaniels aged 9-24 months was performed to describe the ultrasonographic findings of histologically confirmed renal dysplasia. Ultrasonography revealed kidneys of significantly (p < 0.001) reduced volume in all dogs. During qualitative evaluation, two different types of sonographic alterations could be seen. In one type of the ultrasound alterations, corticomedullary demarcation was distinct and the renal cortex was remarkably thin, which was best seen in the dorsal (frontal) imaging plane. In the other type of the ultrasound appearance, overall increased echogenicity with poor corticomedullary demarcation was noticed, and the kidneys could hardly be separated from their surroundings. These features were best recognised in the sagittal (coronal) imaging plane. In one dog with secondary hypercalcaemia, a hyperechoic corticomedullary area was also seen. Post-mortem histological diagnosis revealed renal dysplasia and secondary fibrosis. Based on ultrasound findings alone, renal dysplasia (renal familial disease) can be suspected when small kidneys with thin echogenic cortex are present in young dogs. An ultrasound image, similar to that of fibrotic kidneys (increased overall echogenicity and reduced corticomedullary definition) cannot be differentiated from chronic inflammatory disease and from end-stage kidneys. Therefore, ultrasound-guided biopsy or post-mortem histology is necessary for the definitive diagnosis of renal dysplasia. This is the first study reporting on the ultrasound appearance of renal dysplasia in Cocker Spaniel dogs.