Embryology · Urogenital system
Processus vaginalis: hydrocele and indirect inguinal hernia !
- Malformation
A pouch of peritoneum goes ahead of the testis into the scrotum and should close. If it stays open, fluid (hydrocele) or bowel (hernia) can pass.
Updated 2026-11-01
See it in 3D: Inguinal canal · Spermatic cord · Scrotum · Round ligament of uterus
What it is
The processus vaginalis is an outpouching of peritoneum that runs ahead of the testis through the inguinal canal and normally obliterates, leaving only the tunica vaginalis around the testis. If it stays open, peritoneal fluid or a loop of bowel can travel down it. This explains the indirect inguinal hernia of children, the most frequent operation in paediatric surgery, and the communicating hydrocele.
Embryological cause
- From week 12: peritoneum pouches into the inguinal canal following the gubernaculum, forming the processus vaginalis.
- The testis descends behind this sac and is wrapped by its lower part (tunica vaginalis).
- At the end of gestation or in the first months of life, the part between the deep ring and the testis obliterates.
- If it fails to obliterate, the peritoneal cavity stays connected with the scrotum or labium majus.
- Direct inguinal hernia has a different origin: an acquired weakness of the posterior canal wall, typical of adults.
Markers
- AR
- INSL3
How it presents
- Hernia: an inguinal or scrotal bulge that appears with crying or straining and reduces at rest.
- Incarcerated hernia: a hard, tender mass, irritability and vomiting; in girls it may contain the ovary.
- Communicating hydrocele: an enlarged scrotum, bigger at the end of the day and smaller in the morning.
- Non-communicating hydrocele of the newborn: usually disappears in the first months.
- A girl with bilateral inguinal hernias may have complete androgen insensitivity (a testis in the sac).
Diagnosis
- Diagnosis is clinical.
- Transillumination: a hydrocele lets light through; bowel does not.
- Inguinoscrotal ultrasound in unclear cases: separates fluid from bowel and confirms the testis.
Test yourself
Think of the answer, then tap the question to see it.
Which embryonic structure explains indirect inguinal hernia in children?
A patent processus vaginalis, the peritoneal outpouching that accompanied the testis and failed to obliterate.
Why does a hydrocele that changes size during the day suggest a connection with the peritoneum?
Peritoneal fluid moves in and out through a narrow patent processus vaginalis; it is a communicating hydrocele.
Why is indirect inguinal hernia more common on the right?
The right testis descends later and its processus vaginalis closes later.
What is the female equivalent of the processus vaginalis?
The canal of Nuck, which accompanies the round ligament of the uterus in the inguinal canal.
See it in 3D
The structures of Durgical's 3D anatomy where it is found.
Related
- Gonads and the descent of the testis
- Cryptorchidism
- Differences of sex development: CAH, AIS and 5α-reductase
Related conditions
Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given.
Sources: Hydrocele: MedlinePlus Medical Encyclopedia (MedlinePlus, U.S. National Library of Medicine, 2024); Embryology, Testicle - StatPearls - NCBI Bookshelf (StatPearls Publishing (NCBI Bookshelf), 2023).
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Representative model, for educational purposes only.