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Fetal testis

The fetal testis is the male gonad, responsible for hormone production (testosterone, anti-Müllerian hormone) and future spermatogenesis. It develops from the genital ridge in early gestation and descends through the inguinal canal into the scrotum, usually by the third trimester.

Synonyms

  • Prenatal testis

  • Fetal gonad

  • Male fetal gonadal structure

Structure and Development

  • Derived from genital ridge mesoderm around the 7th gestational week

  • Sertoli cells form seminiferous cords; Leydig cells produce testosterone

  • Initially intra-abdominal, the testes descend under hormonal and mechanical guidance (gubernaculum, intra-abdominal pressure)

  • By the late third trimester, they are normally located within the scrotum

Relations

  • Before descent: Located retroperitoneally near the kidneys, then migrate along posterior abdominal wall

  • After descent: Lie within scrotum, covered by tunica vaginalis

  • Vascular supply: Testicular arteries and veins from abdominal aorta and IVC respectively

Function

  • Produce testosterone, crucial for male genital development

  • Produce anti-Müllerian hormone, leading to regression of Müllerian ducts

  • Prepares for postnatal spermatogenesis by early germ cell development

Clinical Significance

  • Cryptorchidism: Failure of testis to descend (commonest anomaly)

  • Ectopic testis: Abnormal position outside scrotum

  • Testicular tumors (rare in fetus): May be visualized prenatally

  • Sex determination disorders: Abnormal testicular development may underlie ambiguous genitalia

  • Imaging role: Helps confirm normal testicular descent, detect cryptorchidism, hydrocele, or abnormal signal suggesting pathology

MRI Appearance

T2 HASTE (T2 GRE):

  • Testis: Intermediate ovoid structure, darker than surrounding fluid

  • Hydrocele or fluid collections: bright hyperintense

  • Clear contrast with hyperintense amniotic fluid

T1 GRE:

  • Testis: low-to-intermediate signal intensity

  • Fatty tissue in spermatic cord or scrotum: bright

  • Hemorrhage or calcification (rare): focal hyperintensity

MRI image

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

MRI image

Fetal testis mri coronal image