Magnetic resonance angiography versus duplex sonography for diagnosing renovascular disease.

Noninvasive testing for renovascular disease is required to identify patients who may benefit from revascularization procedures without exposing an unnecessary amount of patients to the risks of catheter angiography. All available methods of diagnosing renal artery stenosis have significant limitations. We compared a new technique, contrast-enhanced magnetic resonance angiography, with an established technique, duplex ultrasonography, for the detection of renal artery stenosis using catheter angiography as the standard of reference. Eighty-nine patients with clinically suspected renovascular disease underwent duplex renal scanning and contrast-enhanced magnetic resonance angiography. Sixty of these also underwent catheter angiography. All studies were interpreted for the presence of renal artery stenosis blinded to the results of the other imaging modalities. For detection of hemodynamically significant (>/=60% diameter reduction) main renal artery stenosis, sensitivity and specificity were 90% and 86%, respectively, for magnetic resonance angiography and 81% and 87% for duplex sonography. Most false readings involved differential grading of stenoses detected with all 3 techniques. When patients with fibromuscular dysplasia were excluded from the analysis, the sensitivity of magnetic resonance angiography increased to 97%, with a negative predictive value of 98%. Magnetic resonance angiography detected 96% and duplex 5% of accessory renal arteries seen at catheter angiography. Contrast-enhanced magnetic resonance angiography is a useful technique for diagnosing atherosclerotic renovascular disease. It overcomes the major limitations of duplex renal scanning. However, duplex has the advantage of providing hemodynamic information and appears better suited for the assessment of patients with suspected fibromuscular dysplasia.

Popliteal artery compression and force of active plantar flexion in young healthy volunteers.

PURPOSE: To define the prevalence of popliteal artery occlusion during active plantar flexion in normally active and highly trained young volunteers by measuring plantar flexion force and to assess the force level associated with popliteal artery occlusion. METHODS: Eighty-four limbs of 42 healthy subjects were studied. Eighteen subjects were highly trained athletes, and 24 were normally active persons. Plantar flexion was progressively performed in prone position against a scale. Plantar flexion force was measured in kilograms. After determination of the maximum strength (Pmax) of plantar flexion force, the level necessary to occlude the popliteal artery (Poccl) was assessed by continuously monitoring that vessel using color duplex sonography. RESULTS: Occlusion of the popliteal artery during plantar flexion was observed in 88.1% of the subjects and 77.4% of the limbs. No significant differences in prevalence were found between athletes and normally active subjects. The popliteal artery occluded at a mean plantar flexion force of 45.1 +/- 11.5 kg, which corresponded with 70.1% +/- 16.8% of the maximum force exerted during the provocation test. Poccl was not significantly different between lower limbs of athletes and nonathletes. Although in lower limbs of athletes the popliteal artery occluded at a significantly lower relative force as compared with normally active subjects (65.6% +/- 17.4% vs 74.5% +/- 17.4% of Pmax; p < 0.02), the difference was a result of two extremely low values found in a female athlete. CONCLUSION: Positional occlusion of the popliteal artery during active plantar flexion is commonly found in young healthy volunteers. Prevalence of the phenomenon depends on the force level exerted during active plantar flexion. Popliteal artery occlusion during active plantar flexion is not more frequent in athletes and occurs at a similar force level than in normally active subjects.