Congenital dilatation of the urethral canal is very rare, and generally accompanied by other malformation.
Duplication of the urethra or the existence of two permeable canals is not accepted by all the authors, some of whom contend that one of the canals either terminates in a culdesac or is not separate in itself.
Verneuil has published an article clearly exposing a number of cases, showing that it is possible for the urethra to have two or more canals which are distinct and have separate functions.

Fabricius Hildanus speaks of a double aperture to the urethra; Marcellus Donatus describes duplicity of the urethra, one of the apertures being in the testicle; and there is another case on record in which there was a urethral aperture in the groin.

A case of double urethra in a man of twenty-five living in Styria who was under treatment for gonorrhea is described, the supernumerary urethra opening above the natural one and receiving a sound to the depth of 17 cm.

There was purulent gonorrhea in both urethrae.

Vesalius has an account of a double urethral aperture, one of which was supposed to give spermatic fluid and the other urine.
Borellus, Testa, and Cruveilhier have reported similar instances.
Instances of double penis have been discussed under the head of diphallic terata, page 194.
Hypospadias and epispadias are names given to malformations of the urethra in which the wall of the canal is deficient either above or below.