What about gastric ultrasound?

The point-of-care ultrasound assessment of the stomach has improved in the last year; the main application is to assess its content, both in term of quantity and quality, in order to assess the aspiration risk. This is a central problem for pre-induction assessment, mainly in emergency setting and when the patient is not fully cooperative.

Have a look to the nice website gastricultrasound, with didactic videos and flowcharts, built up by a team of canadian anesthesiologists.

Image from http://www.gastricultrasound.org/index.html