Comparative study of splenic wound healing in young and adult rats

Background: Nonoperative management (NOM) of splenic injuries is a common p ractice in stable trauma patients. Nevertheless, age-related differences in the success rate of NOM have prompted inclusion of age among the criteria of patient selection. Elucidation of the cellular mechanism of splenic moun d healing ill the young versus that of adults may explain why age can be re lated to the success of NOM in splenic injuries. Methods: A laceration was made in the splenic antihilar surface of 40 young and 40 adult male rats. Postoperatively, at specified intervals extending until day 21, spleens mere removed, fixed, and examined by routine histopat hology. In addition, sections were stained histochemically for collagen fib ers and immunohistochemically for myofibroblast histomorphometry. Results: The intense local hemorrhage was resorbed within 48 hours in the y oung rats, and within 7 days in the adults. Disappearance of germinal cente rs and other splenic alterations started on the first day in both groups, b ut regeneration of splenic parenchyma was accomplished after 13 days in the young, whereas in the adults, on day 21 it was still incomplete. Maximal m yofibroblast accumulation at the laceration site was seen after two days in the young, whereas in adults only on day 4 (p < 0.0001), Collagen scars we re not present in either group. Thickening of the damaged capsule, composed of collagen fibers with yellowish-green polarization colors, was observed only in adult rats. Conclusion: Splenic wounds heal by regeneration and not by collagen scarrin g. In the young, myofibroblasts accumulate in the site of injury faster tha n in adults. These cells mag enhance contraction and increase the rate of w ound healing until parenchymatic regeneration is completed, Our results may indirectly explain the higher success rate of NOR-I of splenic injury in y oung patients.