Ultrasonic imaging combined with a pulsed Doppler unit (duplex scanning) allows the noninvasive assessment of blood flow of the superior mesenteric artery. The changes in mesenteric blood flow associated with a standardized (1000 kcal) food load were measured and the results were compared with blood flow of the left common carotid artery. Twenty healthy subjects (aged 30.1 +/- 5 years) were studied fasting (12.4 +/- 2.6 hours' duration) and six times with a 15-minute interval after the test meal. The diameters of the superior mesenteric artery (0.60 +/- 0.09 mm) and of the common carotid artery (0.61 +/- 0.05 mm) were measured from the B-mode image. The Doppler frequency spectra were used to determine peak systolic, late systolic, and end-diastolic velocity and to compute the mean velocity. Although the flow parameters of the common carotid artery were virtually unaffected by food intake, a steep increase in mesenteric blood flow velocity and volume flow was observed. At rest, blood flow through the mesenteric artery was 6.3 +/- 2.6 ml/sec and 9.5 +/- 2.1 ml/sec in the carotid artery. After the test meal, mesenteric artery blood flow increased significantly (p less than 0.0001) and reached maximal hyperemia (20.3 +/- 7.4 ml/sec) after 45 minutes. The measurement of mesenteric blood flow before and after a test meal characterizes intestinal hemodynamics and should be suitable to evaluate ischemic disease and other disorders that lead to changes of mesenteric blood flow.