Testicular torsion

Last revised by Mohammad Salem Amer on 18 Feb 2024

Testicular torsion occurs when a testis 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 are critical if the testis is to be salvaged and testicular infarction prevented.

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.

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

  1. extra-vaginal (supravaginal)
    • 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

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. The hemiscrotum may be swollen or erythematous.

The 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.

It is important to recognize that some patients may present with intermittent symptoms due to spontaneous detorsion, so-called intermittent testicular torsion. This subentity has been increasingly reported in the literature. Short periods of acute groin pain accompanied by vomiting and subsequent spontaneous relief may be typical patient history in these cases 5-7.

Physical examination may reveal elevation of the affected testis, an absence of the cremasteric reflex, transverse lie of the testis, anterior rotation of epididymis, and pain relief with successful manual detorsion.

The TWIST score can be calculated to determine the need for ultrasound 8.

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 adolescents or young adults the more common torsion is intravaginal. The most common underlying abnormality is the so-called bell clapper deformity which is the abnormally high attachment of the tunica vaginalis to the spermatic cord, allowing the testis and adjacent epididymis to move more freely, and thus places it at risk of twisting around the spermatic cord. This deformity is seen in 5-16% of males and is bilateral in 66-100%.

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

Ultrasound is the modality of choice for evaluating the potentially torsed testis. It is simultaneously able to assess the structure of the testis as well as the vascularity, all without subjecting the gametes to ionizing radiation. 

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

The key findings of a torsed testis include 1-3:

  • twisting of the spermatic cord, reflecting etiological mechanism and likely the most specific and sensitive finding in both complete and incomplete torsion 3,5
    • the whirlpool sign refers to a lamellated mass with concentric layering just cephalad to the testis representing the coiled spermatic cord components 13
      • typically visualized using a longitudinal and/or oblique transducer orientation, tilting the imaging plane to visualize course of the spermatic cord
    • twisting or whirling may also be appreciated on color or power Doppler 5
  • altered blood flow
    • incomplete torsion
    • complete torsion
      • an absence of blood flow in both the testis and epididymis
  • increase in the size of the testis and epididymis
  • homogeneous echotexture
    • early finding, before necrosis
  • heterogeneous echotexture
    • a late finding (after 24 hours), implies necrosis
    • hypoechoic regions represent necrosis
    • hyperechoic regions represent hemorrhage (if the testis is reperfused)
  • reactive hydrocele
  • reactive thickening of the scrotal skin with hyperemia and increased flow on color Doppler examination 2
  • peripheral testicular neovascularization
    • only seen after a number of days and represents recruiting and enlargement of small peripheral collaterals
    • only peripheral and patchy portions of the testis are perfused 2

It is important to realize that epididymo-orchitis can closely mimic the appearances of torsion as well as spontaneously detorted 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.

Tc-99m pertechnetate

  • sensitivity of the exam is 80-90%
  • dynamic flow imaging at 2-5 second intervals for 1 minute in the vascular phase
  • 5-minute intervals for tissue phase

The key to successful treatment is rapid diagnosis and surgical intervention. If diagnosed early enough, the testis can be detorted with little damage. If the testis has necrosed, then orchiectomy is required.

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

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

As intermittent testicular torsion ultimately may progress to acute infarction, elective testicular fixation may be indicated and has demonstrated excellent results in smaller series 6,7.

General imaging differentials include:

  • epididymo-orchitis can mimic both
    • torsed testis due to increased intra-testicular pressure
    • spontaneous detorsion with reactive hyperemia
  • testicular abscess
    • avascular heterogeneous areas of the testis
  • testicular tumors
    • enlarged heterogeneous testis
    • usually, flow is present, but some areas may be necrosed and thus avascular
  • torsion of the epididymal appendix
    • this is more of a clinical differential diagnosis
    • testis and epididymis are normal
    • small pedunculated avascular nodule may be seen (very tender)
  • acute idiopathic scrotal edema
    • scrotal wall swelling and edema is characteristic
    • can be unilateral or bilateral
    • marked hypervascularity of the thickened scrotal wall gives rise to the fountain sign on color Doppler ultrasound
    • testis and epididymis are normal in appearance
  • testicular trauma
  • hernia complications
  • tension hydrocele
    • rare cause of testicular ischemia thought to be secondary to hydrostatic pressure elevating intra-tunical pressure with compression of vasculature and restriction of flow 11
    • reversibility of the hemodynamic perturbation after evacuation of the collection and the absence of torsion are suggestive 12

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