Testicular torsion

Testicular torsion occurs when a testicle torts on the spermatic cord resulting in the cutting off of blood supply. The most common symptom is acute testicular pain and the most common underlying cause, a bell-clapper deformity. The diagnosis is often made clinically but if it is in doubt an ultrasound is helpful in confirming the diagnosis. Expedient diagnosis and surgical management if the testis is to be salvaged.

Testicular torsion implies obstruction of first venous, and later, arterial flow. The extent of testicular ischemia will depend on the degree of twisting (180°-720°) and the duration of the torsion. Testicular salvage is more likely in patients treated within 4-6 hours after the onset of torsion.

Differentiation between testicular torsion and epididymo-orchitis is a clinical challenge, since scrotal pain, swelling, and redness or tenderness are clinical symptoms common to these two entities.

Epidemiology

Anatomically there are two types of testicular torsion which occur in different age groups ^2-3: 

1. extra-vaginal (supra-vaginal)
   • torsion occurs at the level of the external inguinal ring
   • seen in neonates
2. intra-vaginal
   • more common variety due to bell clapper deformity (see below)
   • typically occurs in adolescents and young adults

Clinical presentation

The majority of cases of testicular torsion are either spontaneous or in the setting of minor/incidental trauma. In approximately 5-8% of cases, scrotal trauma is significant ¹. 

Onset of severe testicular pain is sudden and is not relieved by elevation of the scrotum ³. There should be no fever or urethral discharge. 

Pathology

In the neonatal form of torsion (extravaginal or supravaginal) the whole content of the hemiscrotum rotates around the spermatic cord at the level of the external inguinal ring ^2-3. 

In adolecents or young adults the more common torsion in intravaginal. The most common underlying abnormality is the so-called bell clapper deformity which allows the testis (and attached epididymis) wide mobility, and thus places it at risk of twisting around the spermatic cord. 

Initially torsion is sufficient only to obstruct venous outflow (incomplete torsion, less than 360 degrees), resulting in gradual increase in intratesticular pressure and resistance. Over time and with additional twisting of the cord (greater than 360 degrees), the arterial inflow is also obstructed and the testis becomes entirely ischaemic ^1-3. 

Radiographic features

Ultrasound

Ultrasound is the modality of choice for evaluating the potentially torted testis. It is simultaneously able to assess the structure of the testis as well as the vascularity, all without subjecting the gametes to ionising radiation. The examination also allows the radiologist to clinically assess the patient and extract any pertinent history. 

The most important part of the examination is comparison to the normal side (see testicular ultrasound technique)

The key findings of a torted testis include ^1-3:

• altered blood flow
  • in incomplete torsion
    • elevated resistive index (RI > 0.75) ³
    • to and fro flow
  • in complete torsion
    • absence of blood flow in both the testis and epididymis
• increase in size of the testis and epididymis
• homogenous echotexture
  • early finding, prior to necrosis
• heterogenous echotexture
  • a late finding (after 24 hours), implies necrosis
  • hypoechoic regions represent necrosis
  • hyperechoic regions represent haemorrhage (if testis is reperfused)
• twisted spermatic cord may be visible ³
• reactive hydrocoele
• reactive thickening of the scrotal skin with hyperaemia and increased flow on colour doppler examination ² 
• peripheral testicular neovascularisation
  • only seen after a number of days and represent recruiting and enlargement of small peripheral collaterals
  • only peripheral and patchy portions of the testis are perfused ²

It is important to realise that epididymo-orchitis can closely mimic the appearances of a both torsion and spontaneously de-torted testis (see differential diagnosis below). The only way to exclude torsion from the differential is if changes are entirely confined to the epididymis with a completely normal testis ². 

Treatment and prognosis

The key to successful treatment is rapid diagnosis and surgical intervention. If early enough the testis can be de-torted with little damage. If the testis has necrosed, then orchidectomy is required. 

Likelihood of salvage of the testis is directly related to the time between onset and de-torsion (whether it be surgical or spontaneous) ³: 

• < 6 hours: ~100% salvage
• 6-12 hours: 50%
• 12-24 hours: 20%

Differential diagnosis

General imaging differentials include

• epididymo-orchitis can mimic both
  • torted testis due to increased intra-testicular pressure
  • spontanous de-torsion with reactive hyperaemia
• testicular abscess
  • avascular heterogenous areas of the testis
• testicular tumours
  • enlarged heterogenous testis
  • usually flow is present, but some areas may be necrosed and thus avascular
• torsion of epididymal appendix
  • this is more of a clinical differential diagnosis
  • testis and epididymis are normal
  • small pedunculated avascular nodule may be seen (very tender)