Inguinal hernia (IH) repair is frequently performed in pediatric surgery, and the condition appears more often in children born prematurely. A key clinical concern is the possibility of developing a metachronous contralateral inguinal hernia (MCIH). This review discusses potential mechanisms involved in pediatric IH formation, with particular focus on how smooth muscle differentiation and fibrotic remodeling may contribute to incomplete closure of the processus vaginalis (PV). It also considers how evolving diagnostic approaches and surgical techniques have shaped contemporary management. In addition, histopathological evaluation may provide further understanding of PV architecture, support more tailored operative decision-making, and help limit the need for subsequent procedures. Overall, the review emphasizes the importance of investigating the histological and ultrastructural features of IHs and hydroceles, and suggests that variations in smooth muscle differentiation and myofibroblast-related changes within the PV may be linked to persistence of patency and susceptibility to herniation.