Local and systemic effects of intraoperative whole-colon washout with 5 per cent povidone-iodine

Background: Segmental intraluminal instillation of several tumoricidal agen ts including povidone-iodine has been advocated to prevent anastomotic recu rrence after colonic resection for colorectal cancer. The local and systemi c effects of on-table whole-colon washout using 5 per cent povidone-iodine were assessed in patients undergoing elective surgery for colorectal cancer . Methods: The local effect of 5 per cent povidone-iodine on the colonic muco sa and the effect of colonic mucosal damage by povidone-iodine on tumour ta ke was first investigated in Fischer 344 rats. In 12 euthyroid non-allergic patients, on-table whole-colon lavage via the appendix was performed. Syst emic (thyroid function) and local (mucosal damage assessed by repeat biopsi es) effects were studied, as well as the in vitro tumoricidal effect of the final anal effluent on tumour cell suspensions. Results: After 30 min of contact with povidone-iodine the rat colonic mucos a was severely injured, with detachment of the epithelial cell layer. Povid one-iodine-induced 'colitis' did not result in tumour development after ino culation of 10(6) Mtln3 carcinoma cells in ten rats. Epithelial desquamatio n was also observed, in all but one patient, 1 and 4 h after colonic lavage . However, epithelial restitution started within I day and no abnormality w as revealed after 3-7 days. Urinary iodine excretion increased markedly and was not within normal values after 1 week. Levels of thyroid hormones decr eased significantly but became normal within 1 week. The anal effluent cont aining povidone-iodine was found to be tumoricidal in vitro on a human colo nic carcinoma cell line and on a tumour cell suspension produced from the p atient's tumour. Conclusion: On-table whole-colon washout using 5 per cent povidone-iodine s eems clinically feasible. This technique deserves further study as a substi tute for preoperative bowel preparation and may help to prevent recurrent c ancer due to implantation of viable exfoliated tumour cells.