Testicular torsion affects roughly 5.5 to 15 out of every 100,000 males per year, depending on the age group studied. It’s uncommon in absolute terms, but it’s one of the most time-sensitive urological emergencies, and it disproportionately strikes two specific age windows: infants under one year old and adolescents around puberty.
Incidence by Age Group
A nationwide study using Japan’s national database found an incidence of about 15 per 100,000 males under age 21 per year, with the rate holding steady across 2018, 2019, and 2020. The 10-to-14 age group had a significantly higher rate than any other, which aligns with what clinicians have long observed: torsion clusters around puberty, when the testes are growing rapidly.
The two peak periods follow a distinct pattern. In a large retrospective study, about 39% of pediatric cases occurred around puberty, while roughly 19% occurred in the first year of life. Neonatal torsion, which includes cases that happen before birth, during delivery, or within the first month, has a separate estimated incidence of 6.1 per 100,000 live births. That number is likely an undercount, since some prenatal cases produce no obvious symptoms and go undetected. In broader populations including adults up to age 35, the rate sits closer to 5.5 per 100,000 males per year.
Why Some Males Are at Higher Risk
The main anatomical risk factor is something called bell clapper deformity, where the tissue that normally anchors the testicle inside the scrotum is missing or inadequate. This lets the testicle hang freely and rotate on its blood supply, like a clapper inside a bell. An autopsy study of 101 testes found this anatomy in 12% of them. That number is far higher than the actual rate of torsion, which means anatomy alone doesn’t cause it. Other triggering factors, such as cold weather, physical activity, rapid testicular growth during puberty, or even sleep, play a role in whether the testicle actually twists.
Bell clapper deformity is almost always present on both sides. This is why surgeons fix the opposite testicle during torsion surgery: if one side twisted, the other side likely has the same vulnerable anatomy.
What Happens Without Quick Treatment
Torsion cuts off blood flow to the testicle, and the survival of that testicle depends almost entirely on how quickly surgery happens. A systematic review of over 2,000 patients broke down salvage rates by time from symptom onset:
- 0 to 6 hours: 97.2% of testicles saved
- 7 to 12 hours: 79.3%
- 13 to 18 hours: 57.3%
- 19 to 24 hours: 42.5%
- 25 to 48 hours: 24.2%
- Beyond 48 hours: 7.4%
The steep drop-off after 6 hours is why torsion is treated as a surgical emergency. Cumulative data shows that within the first 12 hours, about 90% of testicles can be saved. After 24 hours, that number falls below 19%.
How Often the Testicle Is Lost
Nationally in the United States, about 32% of pediatric torsion cases that go to surgery end with the testicle being removed rather than saved. That comes from a study of nearly 2,900 patients. The average age of boys who lost the testicle was about 10.7 years, compared to 12.6 years for those whose testicle was successfully fixed in place. The younger average age in the removal group may reflect the difficulty of recognizing torsion symptoms in younger children, leading to longer delays before reaching the operating room.
One in three is a sobering number, and it underscores how much the outcome depends on speed of recognition. The biology of torsion is straightforward to fix surgically. The challenge is getting to surgery fast enough.
Recurrence After Surgery
Once a testicle is surgically fixed in place, the chance of it twisting again on the same side is very low. A decade-long study tracking outcomes found a recurrence rate of 1.4%, with the two documented recurrences happening 18 and 23 months after the initial surgery. The type of suture used or the number of fixation points didn’t meaningfully change that risk.
This low recurrence rate held regardless of the specific surgical technique, which suggests that once the testicle is anchored, it stays anchored in the vast majority of cases. The contralateral testicle, if fixed at the same time (as is standard practice), carries a similarly low risk going forward.