Topics

Topic

design image
Fetal scrotum

The fetal scrotum is a paired sac-like structure that develops from labioscrotal swellings and encloses the testes after their descent from the abdomen. It becomes recognizable on prenatal ultrasound and MRI in the second and third trimesters and serves as a marker of male sex differentiation.

Synonyms

  • Prenatal scrotum

  • Fetal male genital sac

  • Fetal gonadal sac

Structure and Development

  • Originates from labioscrotal swellings, which fuse in the midline under androgen influence

  • Testes descend into the scrotum via the inguinal canal, usually by the third trimester

  • Consists of scrotal skin, dartos muscle, and underlying connective tissue surrounding testes

Relations

  • Anteriorly: Abdominal wall skin continuity

  • Posteriorly: Perineum

  • Superiorly: Continuous with inguinal region and spermatic cord

  • Contents: Fetal testes, epididymis, and developing spermatic cord structures

Function

  • Houses and protects developing testes

  • Facilitates testicular descent into a cooler environment necessary for postnatal spermatogenesis

  • Serves as a marker of fetal sex differentiation

Clinical Significance

  • Cryptorchidism: Testes fail to descend into scrotum by term

  • Disorders of sex development: Scrotal abnormalities may indicate underlying genetic or hormonal issues

  • Hydrocele: Fluid collection around testes may be present prenatally

  • Imaging role: Confirms male genitalia and helps detect anomalies in testicular descent

MRI Appearance

 

T2 HASTE (T2 GRE):

  • Scrotal sac: bright hyperintense signal due to high water content

  • Hydrocele (if present): also bright, appearing continuous with scrotal fluid

  • Testes inside: appear as bright ovoid foci relative to muscle and pelvic structures

T1 GRE:

  • Scrotal wall: intermediate-to-low signal

  • Testes: low-to-intermediate signal, less bright than on T2

  • Fat within spermatic cord (if visible): bright hyperintense

MRI image

Fetal scrotum MRI axial anatomy image-img-00000-00000

MRI image

Fetal scrotum mri coronal