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Testis

The testis (plural: testes) is the primary male gonad responsible for sperm production and testosterone secretion. Each testis is an ovoid organ located in the scrotum, suspended by the spermatic cord. They are enclosed by a series of protective coverings and divided internally into lobules containing seminiferous tubules.

The testes are essential for male fertility, endocrine regulation, and reproduction. Their superficial location makes them accessible for clinical examination and imaging, while also rendering them vulnerable to trauma, infection, and neoplasms.

Synonyms

  • Male gonad

  • Orchis (historical term)

  • Testicle

Location and Coverings

  • Location: Situated within the scrotum, one on each side, suspended by the spermatic cord

  • Coverings (from superficial to deep):

    • Skin

    • Dartos fascia

    • External spermatic fascia

    • Cremasteric fascia and muscle

    • Internal spermatic fascia

    • Tunica vaginalis (parietal and visceral layers)

    • Tunica albuginea (dense fibrous capsule surrounding testis)

    • Tunica vasculosa (vascular layer deep to tunica albuginea)

Relations

  • Anteriorly and laterally: Tunica vaginalis (visceral layer) and scrotal wall

  • Posteriorly: Epididymis (head, body, tail)

  • Superiorly: Spermatic cord

  • Inferiorly: Scrotal wall and gubernaculum testis (remnant)

Function

  • Spermatogenesis: Production of sperm within seminiferous tubules

  • Endocrine: Secretion of testosterone by Leydig cells, regulating male secondary sexual characteristics and spermatogenesis

  • Storage and maturation: Early maturation of sperm before passage into the epididymis

  • Reproductive role: Essential for fertility and propagation of male genetic material

Clinical Significance

  • Infections: Orchitis and epididymo-orchitis

  • Neoplasms: Testicular germ cell tumors (seminoma, non-seminomatous tumors), stromal tumors

  • Trauma: Hematoma, rupture, torsion

  • Torsion: Urological emergency causing ischemia

  • Congenital anomalies: Cryptorchidism, ectopic testis, microlithiasis

  • Fertility issues: Affected by infections, tumors, or systemic diseases

MRI Appearance

T1-weighted images:

  • Testis shows homogeneous low-to-intermediate signal intensity

  • Mediastinum testis appears as a linear low-signal band

  • Hemorrhage or fat within lesions may appear bright

T2-weighted images:

  • Testis shows homogeneous high signal intensity

  • Mediastinum testis remains dark linear structure

  • Tumors often appear as focal areas of altered signal (intermediate to low or heterogeneous)

STIR (Short Tau Inversion Recovery):

  • Edema, inflammation, or tumor appears bright hyperintense

  • Useful for detecting subtle orchitis or trauma

T1 Fat-Sat Post-Contrast:

  • Normal testis shows uniform moderate enhancement

  • Tumors show heterogeneous or nodular enhancement

  • Infarction/necrosis shows non-enhancing areas

  • Abscess shows rim enhancement

3D T2 SPACE / CISS:

  • Testis appears as intermediate-to-bright ovoid structure relative to muscle

  • Tunica albuginea and mediastinum testis appear as thin dark lines

  • Excellent for delineating testicular microanatomy and detecting subtle lesions

CT Appearance

Non-Contrast CT:

  • Testis appears as a homogeneous soft tissue density structure within the scrotum

  • Calcifications (e.g., microlithiasis, old granulomas) may appear as small hyperdensities

  • Hematoma appears hyperdense acutely

Post-Contrast CT:

  • Normal testis enhances mildly and homogeneously

  • Tumors enhance variably, often heterogeneously

  • Abscesses appear as low-density centers with rim enhancement

  • Trauma: disruption of capsule and heterogeneous enhancement may indicate rupture

MRI image

Testis mri axial anatomy image-img-00000-00000

MRI image

Testis mri coronal image

MRI image

Testis sag mri image