Which flow pattern is observed in the SMA after a meal?

• A. High resistance
• B. Low resistance
• C. Pulsatile
• D. Turbulent

Answer: (B)

After a meal, the splanchnic circulation needs more blood to support digestion, so the vessels supplying the gut, including the superior mesenteric artery, dilate and resistance falls. On Doppler, this creates a low-resistance waveform, meaning there is forward flow throughout the entire cardiac cycle with a notable diastolic component. The diastolic flow increases because the downstream resistance is reduced, so the artery maintains steady forward flow rather than letting flow drop off between systolic peaks. This contrasts with a high-resistance pattern, which would show little diastolic forward flow and a more pulsatile, constricted waveform. Turbulent flow would suggest pathology such as stenosis, which isn’t the normal post-meal pattern. Thus, the postprandial SMA flow pattern is low resistance.