Renal aplasia is complete lack of development of one or both kidneys.
If bilateral, it results in neonatal death. If unilateral, the opposite kidney is hypertrophied and no clinical signs will be present unless the opposite kidney is damaged. Renal aplasia is more commonly recognized in the cat. It may be inherited in beagles. Polycystic diseas e results in multiple cysts of varying size in one or both kidneys.