Background: In order to test the influence of a pneumoperitoneum on the peritoneal implantation of free intraperitoneal colon cancer cells, 40 male syngeneic WAG rats were at random divided into four groups. Methods: Group 1 (n = 10) animals underwent a midline laparotomy and 10(4) CC531 colon cancer cells were injected intraperitoneally (IF); in group 2 (n = 10) 10(4) CC531 cells were injected TP without further manipulation; in group 3 (n = 10) a pneumoperitoneum up to 10 mmHg was created after the IP injection of the same amount of CC531 cells, The pneumoperitoneum was maintained for 15 min, Finally in group 4 (n = 10) after the IP injection of 10(4) CC531 cells and after the creation of a pneumoperitoneum, two 14-G IV catheters simulating trocars were introduced in each flank. A follow-up period of 8 weeks was used, Tumor implantation was scored according to the peritoneal cancer index of Eggermont and the index of Chauffert. Results: Tumor nodules were found varying from 60% in groups 1-3 to 50% in group 4, There was no statistical difference between the implantation rate in the four groups, A port-site recurrence was seen in group 4; all the other tumor implants were located in the mesenterium, omentum, internal genitals, or parietal peritoneum. Conclusions: The presence of a pneumoperitoneum does not enhance the implantation of free intraperitoneal malignant colon cancer cells in the rat, but the presence of a ''port'' may lead to abdominal-wall metastases.
