Accepted 16 October 1995 A 71-year-old man presented with a four-week history of left-sided back and leg pain. Two and a half years previously he had had an aorto-bifemoral prosthetic graft replacement for an inflammatory aortic aneurysm which extended into both iliac arteries. He had a history of ischaemic heart disease and a strong family history of ischaemic heart disease. On examination the only significant finding was marked wasting of the muscles of the left leg. Initial investigations demonstrated degenerative changes in the lumbar spine, to which his symptoms were originally attributed. The left-sided pain had persisted for three months when he was admitted to hospital with an exacerbation of the back pain and left leg pain. A contrastenhanced computed tomography (CT) scan was performed (figure 1).