Case records of 2026 patients operated on because of abdominal aortic aneurysms from 11 Swedish Vascular Centers were reviewed and revealed 98 cases (4.8%) of inflammatory abdominal aortic aneurysm. Also included in this case-control study was an analysis of a randomized group of 82 patients from the same centers who had noninflammatory abdominal aortic aneurysms. Four inflammatory aneurysms were ruptured, compared with 16 in the noninflammatory group (p less than 0.01). A higher proportion of patients with inflammatory abdominal aortic aneurysms had symptoms that led to radiographic investigations. The median erythrocyte sedimentation rate was 39 mm versus 19 mm (26% of patients with inflammatory abdominal aortic aneurysms had erythrocyte sedimentation rates greater than 50 mm; p less than 0.001), and the serum creatinine level was increased in 27 and 8 patients (p less than 0.01) in the inflammatory and noninflammatory groups, respectively. Preoperative investigations revealed ureteral obstruction in 19 patients with inflammatory abdominal aortic aneurysms, of whom 12 had preoperative nephrostomy or ureteral catheter placement. At operation, 20 additional patients exhibited fibrosis around one or both ureters. Although ureterolysis was performed in 19 patients, preoperative and postoperative creatinine levels did not differ between these patients and the conservatively treated ones. Duration of surgery (215 vs 218 minutes), intraoperative blood loss (2085 vs 2400 ml) and complications did not differ significantly between the groups. Overall operative (30-day) mortality was equal (11% vs 12%) but was increased for patients undergoing elective surgery for inflammatory abdominal aortic aneurysms (9% vs 0%; p = 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)