Which three findings must be present to diagnose graft stenosis?

• A. Severe post-stenotic turbulence
• B. All three
• C. 2:1 increase
• D. Focal velocity acceleration

Answer: (B)

Diagnosing graft stenosis with duplex relies on demonstrating three interrelated signs of hemodynamically significant narrowing. First, focal velocity acceleration shows a localized spike in flow velocity right at the narrowed segment, reflecting the conservation of mass as cross-sectional area decreases. Second, a velocity ratio of about 2:1 (stenosis velocity compared with the pre-stenotic segment) indicates that the narrowing is truly causing a meaningful change in flow, not just normal variation. Third, severe post-stenotic turbulence distal to the narrowing confirms disturbed, high-energy flow beyond the lesion, which accompanies a significant constriction.

Together, these three findings provide consistent evidence of a true, hemodynamically important graft stenosis. If one or two criteria are present but not all, the diagnosis is less certain, since each factor supports different aspects of the same problem: the location, the magnitude of narrowing, and the impact on downstream flow.