Scrotum normal
Anatomy
Anterior view scrotal anatomy labelled.
Appreciation of the posterior structures.
Testicular descent
- The gubernaculum (blue) contracts pulling the testicle downwards.
- As the testicle descends through the inguinal canal (green box), the epididymus folds becoming the head, tail and vas deferens (red).
- A reflection of the peritoneum is also pulled down into the scrotum, the tunica vaginalis or processus vaginalis (green)
Normal Images
- The main components when assessing the scrotum with ultrasound are the epididymis, testis, pampiniform plexus, spermatic cord and groin.
- The spermatic cord contains the testicular, cremasteric, and deferential arteries, vas deferens, pampiniform plexus, nerves, and lymphatics.
Normal Testis
Scrotal/testicular ultrasound longitudinal scan plane.
Ensure you slide from medial to lateral and examine the entire testis.
Normal Sagittal Image Testis.
A transverse view of the testis.
A volume measurement of each testis should be recorded.
Scrotal/testicular ultrasound transverse scan plane.
Ensure you slide from top to bottom and examine the entire testis.
Normal testis ultrasound using a curvilinear probe for accurate measurements or to provide a more global view including surrounding anatomy and pathology.
A coronal ultrasound view using a curvilinear probe provides a good comparison and overview of both sides.
Ultrasound of normal testicular vascularity with colour doppler in a post pubescent case.
Colour Doppler should be used to assess for any injury, torsion or orchitis.
Normal Epididymis
Anatomy Scrotum
Normal Sagittal image head of epididymis
The transducer should be moved posterolaterally to view the epididymis body and tail.
The pampiniform plexus is best appreciated lateral to the testis and in the superior portion. It should be dynamically assessed with colour using a valsalva technique to appreciate reflux in the veins.
Colour doppler
- In the pre-pubescent testis, flow can be difficult to identify. Low PRF, colour gain approaching saturation, and light probe pressure are required.
- Post pubescent testes should have readily identifiable venous and arterial scattered flow.
Torsion: Absent flow in one testis when flow is readily visible in the other is suggestive of torsion.
Orchitis: Diffusely increase flow in the testis. If is increased in both the testis and epididymis, it is epididymo-orchitis.
Infarct: Segmental absence of flow. Usually post trauma. There will also be segmental heterogeneity on B-mode.
- Obtain a spectral doppler trace of both arterial and venous flow in the setting of suspected torsion. This may assist in the diagnosis of partial torsion, or tort/untort.
- There are suggestions that resistive indices in intralobar arteries will be elevated (>.75) in the intermittent torsion group.
PITFALLS: Flow must be intratesticular. Not just capsular.
Normal variants
Ductal ectasia
- This is a common finding at rete testis.
- It can extend along mediastinum testis and/or into the epididymis, particularly the epididymal head.
- More common with a past history of vasectomy.
Vas Deferens
- In transverse the vas is a hypoechoic ring with a central echogenic ‘dot’.
- In longitudinal the echogenic dot will be seen as parallel echogenic lines on high frequency probes, deliniating the lumen.
- Post vasectomy the vas may have a larger diameter or be slightly tortuous. It should not be mistaken for a thrombosed vein.
Paediatric Scrotum
Common presentations and likely causes:
- Acute pain – torsion/injury
- Swelling – hernia/hydrocele
- Absence – retractile/cryptorchid
Infection is much less common in prepubescents.
The testes should be imaged together and compared for size and echogenicity.
The normal paediatric testis volume (<8yrs) is 1-2cc.
Spectral Doppler can assist in determining if there is any torsion of the testis. This image shows normal vascularity.
Pediatric TIPS:
Torsion:
- When assessing for vascularity, have a low PRF (<10), turn the colour gain up to saturation then reduce until the flare resolves.
- Light probe pressure.
- Warm gel.
- Check for both arterial and venous flow Document with spectral doppler. Do not rely on colour alone.
- Check the intratesticular arterial resistive index. If >0.75 -> ? partial or intermittent torsion.
- Whirlpool sign: transverse sweep through the cord from the inguinal canal to the scrotum. With and without colour doppler. Look for the spiralling twist in the cord.
Absence
- Careful search is required for the missing testis because of the small size.
- A curvilinear probe may be required if the testis is not in the cord and is in the abdominal cavity.
- If close to the scrotum, attempt to gently relocate the testis.
Role of Ultrasound
Ultrasound is essentially used to investigate causes for:
- Pain
- Which side?
- Dull or sharp?
- Constant or intermittent?
- Acute or chronic?
- Does it travel higher?
- Mass
- Trauma
- Infertility
- Undescended testis
- H/O Trauma, surgery or infection?
- Reduced sperm count
- Varicocele
- Hydrocele
- Infections (orchitis, prostatitis)
- Polycystic kidney disease
- Cryptorchidism
Limitations
- Cold or patient anxiety may cause the scrotum to contract. The thickened, wrinkled scrotal skin is attenuative, reducing detail.
- Whenever possible, use warm gel (and hands).
Patient Preparation
- Must make sure the patient is comfortable.
- Not only is this to put the patient at ease but you will get more information from the patient which will give you better clues as to what the diagnosis will be.
- Using a towel or the patients gown, tuck the penis up over the symphysis to help elevate and immobilise the scrotum.
- Use warm gel.
Equipment setup
- Use of a high resolution probe (7-18MHZ) is essential when
assessing the internal structures of the scrotum. - Low PRF and high gain colour/power/Doppler capabilities when
assessing vessels of a testis. - Be prepared to change frequency output of probe (or probes) to
obtain accurate length measurements, an overview of pathology and anatomy
to each other and adequately assess deeper structures in the abdomen if
necessary.
Common Pathology
Extratesticular Lump or swelling
- Hydrocele
- Epididymitis, Orchitis or Epididymo-orchitis
- Epididymal Cysts
- Varicocele in the Pampiniform plexus
- Cryptorchidism or Maldescent
- Scrotal “Pearl”
- Microlithiasis (intratesticular)
Scrotal swelling with pain – 4 main causes:
- Torsion (20%)
- Infection/inflammation (75-80%)
- Haemorrhage
- Strangulated Hernia
Torsion results in acute testicular infarction and eventually an atrophic testicle and constitutes a medical emergency. Quite often these patients will bypass the imaging department and go straight to theatre.
NOTE:
- epididymitis:torsion = 3:2 <20years
- epididymitis:torsion = 9:1 >20years
Intratesticular Lumps
- Germ Cell Tumours
- Seminoma
- Nonseminoma
SCANNING TECHNIQUE
- Begin with a survey scan transversely down the scrotum to compare echogenicity of the testes.
- Scan each side independently in both longitudinal and transverse planes.
- You may need to apply slight pressure to immobilise the testis as you scan. However, it is important to scan with minimal pressure to visualise fluid overlying the testis.
- Locate the epididymal head and follow in transverse down the body and tail.
- Assess both intra and extratesticular structures with power Doppler.
- The Valsalva manoeuvre or scanning in the upright position should be performed when evaluating for varicoceles or hernias.
- If a varicocele is identified, the scan should be extended to assess the testicular veins for the point of origin. Such as extratesticular masses that could be compressing the vein (e.g. pelvic lymphadenopathy)
- If a hernia is suspected click the link below
Basic Hardcopy Imaging
A scrotal series should include the following minimum images:
- Transverse image showing both testes for comparative echogenicity
- Transverse images of each testis
- Maximum transverse measurement of each testis
- Longitudinal images of each testis
- Maximum longitudinal measurement of each testis
- Epididymis to include the head, body and tail (bilaterally)
- Vascularity of each testis with spectral trace
- Spermatic cord
- Document the normal anatomy. Any pathology found in 2 planes,
including measurements and any vascularity - Groin for lymphadenopathy
- Kidneys