RED (Hereditary and Congenital Diseases Number and Size Anomalies of the Kidney)

Renal agenesis or aplasia

 Kidneys failed to form or develop

 is a relatively rare anomaly occurring in approximately 1 in 1000 live births and is more common in males than females.

 can be detected by prenatal sonography, and it generally manifests as absence of a kidney on one side (unilaterally) and an associated unusually large kidney on the other side (compensatory hypertrophy)

Supernumerary kidney

 which is also relatively rare, involves the presence of a third, small, rudimentary kidney.

 It has no parenchymal attachment to a kidney, and in about half the cases, the supernumerary kidney drains from an independent renal pelvis into the ureter on that side.

 It often becomes symptomatic as a result of infection.

Hypoplasia

 is a rare anomaly of size involving a kidney that is developed less than normally in size but contains normal nephrons

 Usually, is associated with hyperplasia of the other kidney.

Hyperplasia

 it involves overdevelopment of a kidney.