A study was performed with rabbits to examine the efficacy of treatments for fecal peritonitis and, specifically, to determine whether it is beneficial to include antibiotics in the saline used to irrigate the peritoneum. A standardized inoculum of human stool suspension was placed in the peritoneal cavity of the rabbits. Fifty-six rabbits were studied to compare the effect of treatments begun 2 hours after peritoneal soiling. The administration of no treatment resulted in 100% mortality (14 of 14). Parenteral cefotetan 25 mg/kg intramuscularly (IM) twice a day (BID) with no other treatment reduced mortality to 50% (p less than 0.05). Cefotetan 25 mg/kg IM BID plus irrigation of the peritoneum with plain saline further reduced mortality to 21% (3 of 14, p less than 0.05). Cefotetan 25 mg/kg IM BID plus irrigation of the peritoneum with saline containing cefotetan 1.0 mg/mL reduced mortality to 14% (2 of 14, p = not significant). These treatments also produced a progressive decrease in the number of intraperitoneal abscesses from 24.0 +/- 2.1 (mean +/- SEM) in the animals receiving no treatment to 9.7 +/- 1.2 abscesses in the animals receiving peritoneal irrigation with saline containing cefotetan (p less than 0.001). A second experiment then was performed specifically to examine the efficacy of intraperitoneal antibiotics. A lethal fecal inoculum was determined in rabbits receiving conventional therapy, i.e., parenteral antibiotics (cefotetan) and irrigation of the peritoneum with plain saline. With two hours delay before treatment, cefotetan 25 mg/kg IM BID and irrigation with plain saline produced 80% mortality (11 of 14). Cefotetan 25 mg/kg IM BID plus cefotetan 1.0 mg/mL in the saline washout reduced mortality to 21% (3 of 14, p = 0.003) and markedly reduced the number of intraperitoneal abscesses from 13.4 +/- 0.7 in the animals receiving irrigation with plain saline to 8.1 +/- 0.8 in the animals receiving irrigation with saline containing cefotetan (p less than 0.0001). Thus, intraperitoneal irrigation with antibiotics was highly effective. Serum antibiotic levels drawn 30 minutes after irrigation were 112.7 +/- 22.4 micrograms/mL in animals that received irrigation with plain saline, and 101.7 +/- 15.2 micrograms/mL in animals that received irrigation with saline containing cefotetan. These serum levels were not significantly different. With 6 hours delay before treatment, all therapy was less effective. Cefotetan 25 mg/kg IM BID and irrigation with plain saline resulted in 100% mortality (14 of 14). With 6 hours delay, cefotetan 25 mg/kg IM BID and irrigation with saline containing cefotetan reduced mortality to 80% (11 of 14).(ABSTRACT TRUNCATED AT 400 WORDS)