FETAL HYDROCELE

View

ETIOLOGY

• Normal appearance in the third trimester male fetus, as fluid frequently accumulates within the patent processus vaginalis during descent of the testis and epididymis. A small stable hydrocele is probably normal and such fluid is usually absorbed by one year of age.
• Fetal ascites or hydrops.
• Intrauterine intraperitoneal transfusion for non-immune hydrops.

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.

ULTRASOUND

• Although literature suggests that testicular descent occurs between 18 and 32 weeks, hydroceles have been reported from 27 weeks until term.
• "Owl sign" (1).

ASSOCIATIONS

• Fetal hydrops.
• Meconium peritonitis (2).
• Inflammation from Meckel diverticulum (3).

DIFFERENTIAL DIAGNOSIS

1. Testicular torsion:

· Mostly unilateral and on the left side.

· Acute phase - hypoechogenic testicle (due to edema) or a heterogeneous pattern (due to necrosis), but a hydrocele can be an early sign of a testicular torsion.

· Chronic phase - a small rounded, hypoechogenic area, with a peripheral echogenic ring due to calcium deposits.

2. Inguinoscrotal hernia - rare scrotal mass with multicystic structure. Peristaltic movements can occasionally be observed.

PROGNOSIS

Hydroceles are a common antenatal finding that should be viewed as physiologic as long as no other fetal abnormalities are detected (4).

REFERENCES

1. Sherer DM, Smith SA. Suggested "Owl Eye Sign" in fetal sonography. J Ultrasound Med 1990;9:690.
2. Ring KS, Axelrod SL, Burbige KA et.al. Mecomium hydrocele: An unusual etiology of a scrotal mass in the newborn. J Urol 1989;141:1172.
3. Wright JE, Bhagwandeen SB. Antenatal perforation of Meckel's diverticulum presenting as an inflamed hydrocele. J Pediatr Surg 1986;21:989.
4. Pretorius DH, Halsted MJ, Abels W et.al. Hydroceles detected prenatally: Common physiologic phenomenon. J Ultrasound Med 1998;17:49-52.