Retardation of healing of large-bowel anastomoses by 5-fluorouracil

Experiments were performed to test the hypothesis that 5-Fluorouracil (5-FU) would delay or prevent healing of large-bowel anastomoses. The caecums of 120 specific-pathogen-free rats were transected and reanastomosed at once. Daily intravenous injections of 5-FU were given to half the rats, the other half being controls and receiving an equal volume of saline. At Days 5, 7 and 10, standard-sized sections of sutire line were pulled apart, and the force required to do this was recorded. At five days the strengths of the anastomoses in the 5-FU treated animals were only 25% of that of the controls, but by ten days they were over 60% of the strength of the controls. It was concluded that 5-FU delayed, but did not prevent, healing, and that it would be safe to use it in the early postoperative period, but not until several days after operation.