This paper describes a meta-analysis using an electronic database search with keywords to elucidate epidemiology and presentation of familial testicular torsion. The authors found that up to 10% of patients with testicular torsion have an affected first degree relative. Family history is missed in up to 27% of affected families. There is a high concordance rate or bilaterality amongst monozygous twins, and a high rate of bilaterality in other relatives. The authors also found that familial torsion tends to occur in the same age range within families – ‘age-related clustering’. The genetic theory of inheritance is supported by animal studies in INSL3 knock-out mice. These studies have demonstrated that abnormalities in testicular attachment and rate of testicular torsion occur in a gene dose-dependent manner. In addition INSL3 is an established risk factor for undescended testis in humans, supporting the theory that INSL3 is involved.