The effect of elevated oxygen on kidney stone twinkling in vivo and ex vivo

Abstract

The Doppler ultrasound twinkling artifact is a rapid color shift observed in ∼66% of kidney stones. Breathing oxygen at elevated pressures was shown to enhance twinkling on kidney stones in human subjects. Here, in humans and in ex vivo stones, we investigate the effects of elevated oxygen at ambient pressure. Recruited subjects with confirmed stones were scanned with a research ultrasound system and Philips/ATL C5-2 transducer while breathing ambient air for 2 min. Then, subjects were masked with 100% oxygen for 15 min and scanned again for the last 2 min. Similarly, ex vivo stones were imaged before and after bubbling oxygen into water. Average Doppler power was calculated for in vivo and ex vivo stones. In human subjects, Doppler power increased by 30% when subjects breathed pure oxygen compared to ambient air. Similarly, on ex vivo stones, an average increase in Doppler power of 98% was observed in elevated oxygen conditions; twinkling also became visible on stones that otherwise did not twinkle at elevated oxygen (50% more oxygen than control). These results suggest that elevated oxygen at ambient pressure may improve the consistency of twinkling to detect kidney stones. [Work supported by the PSU Center for Biodevices Seed Grant.]