Can you tell me what the causes could be for a surgery for undescended testis can be?

Minor birth defect: Approximately 1 - 2% of boys have testicular maldescent requiring surgery. 3% of full-term baby boys ; 30% of preemies., most descend spontaneously by age-6-months. Some have udts following hernia surgery. Surgery indicated for non-palpable testes to reduce slight risk of cancer in later life, maximise fertility potential, psychologic to achieve normal appearance ; reduce risk of trauma or torsion.