[Specular crossed renal ectopia and balanic hypospadias in monozygotic twins]

The observation of a balanic hypospadia with chordee associated with a renal malformation in both of identical twins is reported. Monozygosity of twins was demonstrated with the study of ABO, MNS, HLA and RH factor systems. Urography, performed in both twins, showed a specular crossed renal ectopia with fusion. Abdominal ultrasounds, Chest-X-ray and barium meal showed no other abnormalities. After an analysis of the embryogenetic mechanisms of twinning, the Authors elaborate a hypothesis to explain the development of this specular renal malformation, never reported up to date in identical twins.