Recirculation zone length in renal artery is affected by flow spirality and renal-to-aorta flow ratio.

Haemodynamic perturbations such as flow recirculation zones play a key role in progression and development of renal artery stenosis, which typically originate at the aorta-renal bifurcation. The spiral nature of aortic blood flow, division of aortic blood flow in renal artery as well as the exercise conditions have been shown to alter the haemodynamics in both positive and negative ways. This study focuses on the combinative effects of spiral component of blood flow, renal-to-aorta flow ratio and the exercise conditions on the size and distribution of recirculation zones in renal branches using computational fluid dynamics technique. Our findings show that the recirculation length was longest when the renal-to-aorta flow ratio was smallest. Spiral flow and exercise conditions were found to be effective in reducing the recirculation length in particular in small renal-to-aorta flow ratios. These results support the hypothesis that in renal arteries with small flow ratios where a stenosis is already developed an artificially induced spiral flow within the aorta may decelerate the progression of stenosis and thereby help preserve kidney function.

Particle image velocimetry study of aorta-renal bifurcation.

BACKGROUND: Haemodynamic parameters such as separated flow regions play a key role in the progression and development of atherosclerotic lesions in renal arteries, which typically originate at the renal ostium. OBJECTIVE: The aim of this study was to analyse the flow dynamics in a two-dimensional model of aorta-renal bifurcation, with a particular focus on the effect of aorta-to-renal flow ratio on flow separation regions. METHOD: A particle image velocimetry (PIV) experiment was conducted in an acrylic model of the aorta-renal ostium and the relationship between renal-to-aorta flow ratio and separated flow region was investigated. RESULTS: For high flow ratios, a stagnation region was observed near the cranial side of the aorta. With a decrease in the flow ratio, however, this stagnation region disappeared. Furthermore, our results showed that an increase in the renal flow rate was associated with an increase in the length of the separated flow region, but a decrease in the width of the separation regions. CONCLUSIONS: As the renal-to-aorta flow ratio increased a longer separation region was observed on the cranial side of the renal channel.