Background/Purpose: This report compares the ultrastructure of the newborn and adult liver and emphasizes that the newborn liver is very prone to iatrogenic rupture resulting in a high morbidity and mortality. This study describes the methods used to treat this condition and suggests that pack tamponade may be the method of choice to control hemorrhage. Methods: latrogenic liver rupture with blood loss greater than 35% estimated blood volume occurred in seven patients. Cause of rupture included perihepatic dissection (left lobe mobilization [n = 2], capsule breached surgically [n = 1]), and retraction (n = 3) or prosthetic silo manipulation (n = 1). Results: Initial attempts to control the hemorrhage were unsuccessful in six of seven patients. The on ly secure method to obtain long-term control of the bleeding was perihepatic pack tamponade. Control was incomplete in one patient who had an associated coagulopathy. Transfusion-induced clotting defects were present in four cases. Pack removal at 24 to 96 hours was successful in five of six patients where the bleeding was stopped, the patient fully stabilized and coagulopathy was corrected. Pack removal caused renewed bleeding in one patient, and repacking was unsuccessful. Ultrastructural differences between newborn and adult livers were investigated. The newborn liver contains little fibrous stroma a nd has a very thin capsule, Suture hepatorraphy therefore is an inappropriate technique in most instances and contraindicated if a coagulopathy is present. Surface coagulation and pack tamponade may be the only options available, A single patient in this series survived this complication. Conclusions: This review documents the serious nature of iatrogenic liver injury. Blood loss must be strictly limited by obtaining immediate control of the hemorrhage. If surface control is unsuccessful, pack tamponade should be used. Suturing the newborn liver (especially premature) produces unpredictable results. These observations suggest that pack tamponade is an effective method of controlling bleeding from the liver surface. Copyright (C) 1997 by W.B. Saunders Company.