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The ability of duplex ultrasound graft surveillance to detect graft stenosis is well documented. However, the optimal time to commence duplex ultrasound graft surveillance is not clear.An early duplex ultrasound study was performed on 90 infra-inguinal bypass grafts within 2 weeks of surgery. Further duplex scans were performed at intervals after surgery of 1 month, 3 months, 6 months, 1 year and then annually. An ankle/brachial systolic pressure index (ABI) was performed before the infra-inguinal bypass and then 24 h after the surgery. The ABI was also routinely measured at the time of each graft duplex examination.Six graft thromboses (6.7%) were demonstrated on the first graft duplex within 2 weeks of the surgery. The 24-hour post-operative resting ABI were less than 0.5 in all six cases. Significant graft stenoses (> 50%) or native artery diseases were detected in six cases (6.7%) on the first graft scan (proximal anastomosis stenosis, 1; mid-graft stenosis, 3; peroneal artery stenosis, 1; popliteal artery occlusion, 1). The resting ABI was less than 0.5 in one of these cases. Vein patch angioplasty was performed on graft stenosis in two cases following the first duplex scan. In 78 cases with either normal or minimal graft/native artery stenosis (< 50%), the resting ABI were less than 0.5 in only two cases (2.6%). The first graft duplex ultrasound examinations were technically difficult or gave a poor image in 21 cases (23.3%). During the subsequent graft duplex follow-up, seven graft thromboses were demonstrated at an average of 5.9 months after surgery (1-12 months). Significant stenosis (> 50%) was demonstrated in 10 additional cases at an average of 8.5 months after surgery (1-12 months).The data of the present study do not support routine peri-operative graft duplex scanning in addition to a 1-month graft duplex scan. Early postoperative resting ABI should be routinely performed. If the resting ABI is less than 0.5, an immediate duplex scan should be carried out to assess graft integrity. A long-term non-invasive graft surveillance programme is important in the detection of graft stenosis.