The impact of the intra-abdominal space on liver regeneration after a partial hepatectomy in rats.

Little is known about the relationship between intra-abdominal space and liver regeneration. The present study was experimentally designed to investigate the influence of the "occupied space" or the "loss of occupied space" on a regenerating liver.Experiment 1: Rats were randomly assigned to two groups: SO (space occupied) rats (n = 40); occupancy of intra-abdominal space followed by a two-thirds partial hepatectomy (PH) and control rats (n = 40); A PH alone. The rats in both groups were euthanized at 24, 48, 96, and 168 h after the operation. Computed tomography (CT) images were analyzed to evaluate the regenerating-direction and the shape of the regenerated remnant liver. The liver to body weight ratio and the proliferating cell nuclear antigen (PCNA) labeling index were measured at each time point. Experiment 2: A second laparotomy was performed at 168 h after the PH in both groups; occupier-removal for the SO rats and a sham operation for the control rats. The rats in both groups were euthanized at 24 and 168 h after the second operation. The liver to body weight ratio and PCNA labeling index were measured at each time point.Experiment 1: The remnant liver of the SO rats enlarged toward the dorsal and caudal side because liver regeneration toward the ventral side in the SO rats was inhibited with the occupier in the abdominal space at 96 h, and later, after the PH. CT images showed a statistically significant difference in the shape of the regenerated remnant liver between the control group and the SO group. The liver/body weight ratio was significantly decreased in the SO rats at 96 and 168 h after PH (P < 0.05). There was no significant difference between the groups in the PCNA labeling index. The SO rats showed a significant increase of the PCNA labeling of the inferior right lobe (10.6%) in comparison with the index of the superior right lobe (7.8%), which came in direct contact with the occupier, at 96 h after the operation (P < 0.05). The cell density of superior right lobe of the SO rats group was significantly higher than that of the control group at 168 h after operation (P < 0.05). Experiment 2: There was no statistically significant difference in the liver/body weight ratio at 168 hrs after the second operation between the groups. However, there was a statistically significant increase of the PCNA labeling index 24 h after the second operation in the occupier-removal rats in comparison with the control rats (P < 0.05).The occupied intra-abdominal space was therefore found to suppress liver regeneration after a partial hepatectomy, while the removal of such an occupied space stimulated the regeneration of the liver.