Testicular and scrotal ultrasound

Dr Dan J Bell and Dr Matt A. Morgan et al.

Testicular and scrotal ultrasound is the primary modality for imaging most of the male reproductive system. It is relatively quick, relatively inexpensive, can be correlated quickly with the patient's signs and symptoms, and, most importantly, is non-ionising.

MRI is occasionally used for problem solving if the diagnosis is unclear on ultrasound. CT is only rarely needed, and is avoided because of its ionising radiation. Nuclear medicine studies (e.g. Tc99m-pertechnetate) have also fallen out of favour because of their ionising radiation.

  • homogeneous echogenicity
    • a prepubertal testis has a slightly decreased echogenicity relative to an adult
  • mildly coarse echotexture
  • adult diameter measures between 3-5 cm, with a volume of ~20 ml
  • the tunica (vaginalis/albuginea) appears as an echogenic outline of the testicle:
    • the tunica invaginates to form the linear echogenic testicular mediastinum
  • the rete testis can be identified in ~20% of patients
    • hypoechoic region near the mediastinum
    • more noticeable if dilated
  • appendix testis: attached to upper pole of testicle, near the epididymis
    • not usually seen unless torted
  • spectral Doppler: the testis demonstrates a low-resistance arterial waveform
  • epididymal head: round or oblong structure located near the superior pole of the testicle
    • isoechoic or mildly hyperechoic relative to the testicle
    • measures 5-12 mm
  • epididymal body: extends down the posterior aspect of the testicle
    • measures 2-4 mm
  • epididymal tail: curved structure at the inferior pole of the testicle and becomes the proximal ductus deferens
    • measures 2-5 mm
  • appendix epididymis: attached at the epididymal head
    • not normally seen unless torsed
  • spectral Doppler: epididymis demonstrates a low-resistance arterial waveform
  • normal scrotal skin thickness varies between 2-8 mm

A high-frequency transducer (9-15 MHz) is usually used for evaluation of testicles and scrotum, except in certain circumstances (e.g. massive hydrocele), when a lower MHz transducer is used.

  • patient is supine
  • scrotum is supported on a towel laid over the thighs
  • testicles should be evaluated in both long and short axes
    • if a scrotal mass is found, one of the primary roles of ultrasound is to determine if it intratesticular or extratesticular
      • intratesticular mass: generally malignant
      • extratesticular mass: 3-6% malignant
  • colour and spectral Doppler parameters should be set for low flow
  • important: both a short axis grayscale and a colour Doppler image should be obtained which image both testicles at the same time ("buddy shot" or "sunglasses view"), to compare relative echogenicity and blood flow
  • scrotum should be examined for extratesticular masses or processes
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Article information

rID: 33262
System: Urogenital
Section: Approach
Synonyms or Alternate Spellings:
  • Testicular ultrasound
  • Scrotal ultrasound
  • Testis ultrasound
  • Testicular USS
  • Scrotal USS
  • Testis USS

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    Case 1: scrotal cellulitis
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