The ultrasound itself takes around 40 minutes from start to completion.
Then after the ultrasound is done the results will be sent off to another doctor for the test results and then the doctor will schedule a follow up appointment for you to come back in and get the results.
The results from an ultrasound usually take 2 to 3 days for the results of the ultrasound to come back.
So you should hear back about the ultrasound results in 3 days at most and if not you should call the doctor to find out what is going on.