Etiology of Testicular Torsion
Primary Mechanism
Testicular torsion results from twisting of the spermatic cord, which compromises blood flow to and from the testicle, leading to acute ischemia. 1 The underlying cause differs based on age, with distinct anatomical mechanisms in neonates versus adolescents.
Age-Specific Etiologic Mechanisms
Neonatal/Perinatal Torsion (Extravaginal Type)
- Extravaginal torsion occurs when the entire testis and tunica vaginalis twist together on the spermatic cord, typically happening prenatally or perinatally before the tunica vaginalis becomes fixed to the scrotal wall. 2
- This accounts for approximately 10% of all pediatric testicular torsion cases. 2
- The mechanism involves twisting external to the tunica vaginalis, distinguishing it from the intravaginal type seen in older patients. 2
- While rare, extravaginal torsion can occasionally occur in adolescents, as documented in a 16-year-old male, though this represents an exceptional presentation. 3
Adolescent/Young Adult Torsion (Intravaginal Type)
- The "bell-clapper" deformity is the primary anatomical predisposition in postpubertal males, found in 82% of patients with intermittent testicular torsion. 1
- This deformity involves abnormal fixation of the tunica vaginalis, allowing the testis to rotate freely within the scrotum like a "clapper in a bell." 1
- The MRI "split sign" (hyperintense T2 signal between the posterior epididymis and scrotal wall) can identify this deformity with 83% sensitivity. 1
Bimodal Age Distribution
- Testicular torsion demonstrates a bimodal distribution with peaks in neonates and postpubertal boys, occurring more frequently in adolescents than adults. 1, 2, 4
- The estimated yearly incidence is 2.9 to 3.8 per 100,000 boys under 18 years of age. 1
- Between these peak periods (ages 1 month to 11 years), torsion can still occur but is less common, with an average age of 5 years in one surgical series. 5
- Testicular torsion is rare in patients over 35 years of age. 1
Pathophysiology of Vascular Compromise
- Venous obstruction occurs first due to thinner vessel walls and lower pressure in veins compared to arteries. 1
- Arterial occlusion follows, ultimately leading to testicular ischemia. 1
- Complete torsion exceeding 450 degrees results in absent arterial and venous flow. 1
- Partial torsion presents with diminished arterial velocity and decreased diastolic flow, as venous compromise precedes complete arterial occlusion. 1
Critical Clinical Context
- The exact cause of why torsion occurs at specific times remains unknown, though it tends to occur more frequently during adolescence. 6
- The condition can occur at any age, though the anatomical mechanism differs between neonatal and adolescent presentations. 2
- The presence of bell-clapper deformity bilaterally necessitates bilateral orchiopexy during surgery to prevent contralateral torsion. 1