The pneumoperitoneum and its role in tumor seeding.

Port site recurrences (PSR) are abdominal wall recurrences that occur within a trocar site after cancer laparoscopy and that are not associated with peritoneal carcinosis. The short clinical delay of occurrence of PSR (median 190 days in colorectal cancer) suggests a massive cell seeding into the abdominal wall (over 10(6) cells) during the operation. In human and animal studies, CO2 was not able to aerosolize large numbers of tumor cells using pressures of 8-15 mm Hg, even though isolated mesothelial cells have been found in the aerosol. Such large numbers of tumor cells have only been demonstrated on instruments and trocars. PSR occur not only after CO2 laparoscopy, but also after thoracoscopy, where no CO2 is used. Gaseless laparoscopy was able to reduce, but not to eliminate port site contamination in animal models. Tumor growth was enhanced in numerous animal models using CO2, suggesting an adjuvant effect on tumor growth in the trocar wound. Nevertheless, reported clinical incidences between 0 and 21% suggest that PSR might be a surgeon-related variable dependent mainly on experience and technical expertise. Technical measures have been proposed that might reduce the incidence of PSR.