Renal dysgenesis
Renal dysplasia refers to a kidney volume that is more than 50% smaller than normal, but the development and differentiation of the nephrons are normal, and the ureters are also normal. Renal dysplasia can be unilateral or bilateral. In unilateral cases, the contralateral kidney often has compensatory hypertrophy. True renal dysplasia is a congenital disease that only manifests as small kidney size but normal renal parenchyma. Segmental renal dysplasia, also known as Ask-Upmark kidney, is characterized by small kidney size and one or more deep grooves on the surface of the kidney. The renal parenchyma below it has thyroid-like appearance, and reflux is its possible cause.