Renal hypoplasia is an abnormality that a person is born with in which one or both of the kidneys are smaller than normal (hypoplastic) but with normal structure.It is defined as abnormally small kidneys, where the size is less than two standard deviations below the expected mean for the corresponding demographics, and the morphology is normal. Disease severity depends on whether hypoplasia is unilateral of bilateral, and the degree of reduction in the number of nephrons. [Source: Wikipedia 
]
