A diagnosis of labial hydrocele [hydrocele of Canal of Nuck] was made, the cause for which was not known. These are the postnatal photographs:

A similar photograph demonstarting labial hydrocele is seen in another fetus who had congenital cytomegalovirus infection:

Hydrocele of the canal of Nuck is not a very commom disorder and is one of the differentials of an inguinal mass seen in a female fetus. The canal of Nuck is formed by a small evagination of parietal peritoneum or processus vaginalis which is patent in the fetus, but soon obliterates. Its failure to obliterate may result in an hydrocele or a hernia. Hydrocele of the canal of Nuck has been described to be the female counterpart of the spermatic cord hydrocele in the male.

The fetus may present with a non-tender, fluctuant mass right from birth and extending from the inguinal region into the ipsilateral labium majus. Rarely, it is known to be bilateral. A rare complication noted in literature of this entity is infection of the hydrocele. Surgical excision of the hydrocele is the treatment of choice.


References:

1. Anderson CC, Broadie TA, Mackey JE, Kopecky KK. Hydrocele of the canal of Nuck: ultrasound appearance. Am Surg. 1995 Nov;61(11):959-61.
2. Schneider CA, Festa S, Spillert CR, Bruce CJ, Lazaro EJ.Hydrocele of the canal of Nuck.N J Med. 1994 Jan;91(1):37-8.
3. Stickel WH, Manner M. Female hydrocele (cyst of the canal of Nuck): sonographic appearance of a rare and little-known disorder.J Ultrasound Med. 2004 Mar;23(3):429-32.
4. Ameh EA, Garba ES.Infected hydrocoele of the canal of Nuck in a neonate. Urol Int. 2003;71(2):226-7.