Patients with a ruptured abdominal aortic aneurysm (AAA) are at risk of developing colonic ischaemia after surgery. It is difficult to diagnose this ischaemia at an early stage. D-lactate is produced by intestinal bacteria after ischaemia. L-lactate is released in increased amounts during hypoxia by anaerobic metabolism. This study investigated both variables as a marker for intestinal ischaemia in patients with a ruptured AAA.Twenty-four patients with ruptured AAA were divided retrospectively into two groups with and without ischaemic complications, as verified by colonoscopy. Blood had been taken on admission to the intensive care unit (ICU). Median time to colonoscopy was 9 days after surgery. As controls, four patients with pneumonia, six healthy subjects, five patients with an elective AAA repair, and six patients with sepsis and acute tubular necrosis were included.D-lactate level on admission was significantly increased in patients with colonic ischaemia after ruptured AAA compared with the level in patients without ischaemia (P<0.05), patients with sepsis (P<0.001), those with pneumonia and healthy subjects (P<0.01). L-lactate concentration was similar in the group with intestinal complications and in patients without colonic ischaemia; however, L-lactate levels were higher in patients with pneumonia and sepsis than in healthy subjects (P <0.05).On admission to the ICU, D-lactate, but not L-lactate, levels may predict later colonic ischaemia following repair of a ruptured AAA.