Undescended Testes Growth Potential in Relation to Testis Position from Diagnosis until Puberty

Background: Testicular volume (TV) and testicular atrophy index (TAI) were used to determine criteria for normal, hypotrophic and atrophic undescended testes (UDT). Objectives: This study aimed to determine changes in TV and TAI in patients with different types of UDT. Materials and Methods: 182 boys (aged 0.3-14.0 years) with 212 UDTs were assessed twice 24 months apart. Testes were unilateral (UCT) or bilateral canalicular (BCT) and intra-abdominal (IAT). Results: At the beginning of the observation, the highest TAI was observed in IAT and the lowest in the BCT group (38.1 vs. 12.5%, p < 0.05). After 2 years, the highest TAI was observed in the BCT and IAT groups (20.5 and 19.1%), while the lowest was in the UCT group (12.0%, p < 0.05). At the beginning and after 2 years, the highest TAI was observed in boys aged < 6 years (25.0%, 18.2%) and the lowest in pubertal boys aged 12-14 years (5.9%, 7.3%, p < 0.05). A total of 78.3% of patients at the beginning and 86.8% at the end of the observation had TAI < 30%. Furthermore, 7% of boys at the beginning and 3% at the end of the observation had TAI > 50%. IATs have the highest testicular growth potential (TGP), while BCTs have the lowest (120.0 vs. 28.6%, p < 0.05). The highest TGP was in boys aged < 3 years (100%, p < 0.05) and boys aged 12-14 years (98.1%, p < 0.05), while the lowest was in boys aged 9-10.9 years (19.5%, p < 0.05). Conclusions: We revealed the continuous growth of UDTs until puberty independently of their position. IATs revealed high growth potential.