*Vrije Universiteit Brussel  and ^&Women's Health Alliance, Nashville TN

Synonyms: none

Definition: a collection of serous fluid in a sacculated cavity. In practice the term is mostly used to describe a fluid collection in the tunica vaginalis testis.

Etymology: From the Greek: udro = water and kele = hernia.

Embryogenesis and pathogenesis:

Between the seventh week and birth, the testes descend into the scrotum due to shortening of the gubernaculum. The testes pass through the inguinal canal in the anterior abdominal wall. After the 8^th week, a peritoneal evagination, the processus vaginalis, forms just anterior to the gubernaculum. It forms the inguinal canal by pushing out sock-like extensions of the transversalis fascia, the internal oblique muscle and external oblique muscle, The inguinal canal extends from the base of the inverted transversalis fascia (the deep ring) to the base of the everted external oblique muscle (the superficial ring). After the processus vaginalis has evaginated into the scrotum, the gubernaculum shortens and pulls the gonads through the canal. The gonads always remain within the plane of the subserous fascia associated with the posterior wall of the processus vaginalis. By the end of the pregnancy the testes have completely entered the scrotal sac. The gubernaculum is reduced to a ligamentous band attaching the inferior pole of the testis to the scrotal floor. Within the first year after birth the superior part of the processus vaginalis is usually obliterated leaving a distal remnant sac, the tunica vaginalis, which lies anterior to the testis. Its lumen is normally collapsed but sometimes it may fill with serous secretions forming a testicular hydrocele[1].

Prevalence:

Hydrocele is the most common scrotal anomaly detected during routine prenatal scanning. The frequency is unknown. However, a study of Pretorius et al reported an overall prevalence in male fetuses of 15%. A hydrocele was demonstrated from 27 to 32 weeks of gestation in 21% percent of the fetuses and in 11% between 33 and 41 weeks of gestational age.

Sonographic findings:

Enlarged scrotal sac with a "half moon†of fluid surrounding the testis. There is also a 1 MB video-clip.

Differential diagnosis:

·         prenatal testicular torsion: occurs mostly unilateral and on the left side;

sonographic findings are

1.       in the acute phase: a hypoechogenic testicle (a sign of edema) or a heterogeneous pattern due to necrosis, but a hydrocele can be an early sign of a testicular torsion;

2.       in the chronic phase: a small rounded, hypoechogenic area, with a peripheral echogenic ring due to calcium deposits[4].

·         fetal inguinoscrotal hernia: rare: scrotal mass with multicystic structure. Peristaltic movements can be observed2.

·         uncommon presentation of meconium peritonitis^,6.

Associated anomalies: meconium peritonitis5[6]^,[7]

Prognosis and management: In the absence of other abnormalities a hydrocele is mostly a physiologic finding that resolves spontaneously with no significant sequelae3.

References:

[2] Paladini D. Palmieri S. Morelli PM. Forleo F. Morra T. Salviati M. Zampella C. D’Angelo A. Martinelli P. Fetal inguinoscrotal hernia: prenatal ultrasound diagnosis and pathogenetic evaluation. Ultrasound Obstet Gynecol 1996;7(2):145-6

[3] Pretorius DH. Halsted MJ. Abels W. CatanzariteVA. Kaplan G. Hydroceles identified prenatally: common physiologic phenomen? J Ultrasound Med 1998;17:49-52

[4] Devesa R. Munoz A. Torrents M. Comas C. Carrera JM. Prenatal diagnosis of testicular torsions. Ultrasound Obstet Gynecol 1998;11(4):286-8

[5] Kenney PJ. Spirt BA. Ellis DA. Patil U. Scrotal masses caused by meconium peritonitis: prenatal sonographic findings.Radiology 1985;154(2):362

[6] Ring KS. Axelrod S. Burbige KA. Hensle TW. Meconium hydrocele: an unusual etiology of a scrotal mass in the newborn. J Urol 1989;141(5):1172-3

[7] Sukcharoen N Prenatal sonographic diagnosis of meconium peritonitis: a case report. J Med Assoc Thai 1993 Mar;76(3):171-6