During shock or multiple organ dysfunction syndrome, translocation of bacteria and/or lipopolysaccharide (LPS) from the ischaemic gut might occur and could explain the excess of cytokine production detectable in plasma. To test this hypothesis, we studied a model of mild gut ischaemia due to bowel manipulation and aortic clamping in patients undergoing abdominal aortic surgery (n = 14). Per-operative levels of LPS and cytokines were measured before clamping and after reperfusion, and compared in systemic and portal blood. Systemic levels of LPS and cytokines were measured in a control group of patients undergoing internal carotid surgery (n = 7). Portal LPS was detectable (i.e., > 12 pg/ml) in 36% of the patients undergoing aortic surgery after bowel manipulation, and in 71% after clamp release. Similar levels of LPS were observed in portal and systemic blood after clamp release. Circulating tumour necrosis factor alpha (TNF-alpha) was observed in all patients undergoing aortic surgery. Levels of portal TNF-alpha were higher than those in systemic blood after bowel manipulation as well as after reperfusion (P = 0.02 and 0.007, respectively). LPS was never detected in control patients and TNF-alpha was detectable in only two out of seven patients. Mean levels of IL-6 were similar in the two groups, with a peak on the day following surgery, confirming that circulating IL-6 is associated with any surgical procedures. Our data indicate that bowel manipulation, aortic clamping and reperfusion lead to similar levels of portal and systemic circulating LPS.(ABSTRACT TRUNCATED AT 250 WORDS)