No Oil Pressure Volvo V70

First, have you checked under the vehicle to see where the leak is coming from? If the oil ran straight out, it sounds like the drain plug fell out. If you had to start it to cause it to leak, it could be a loose oil filter.

Check the drain plug at the bottom of the oil pan. Something tells me it wasn't tightened at the last oil change and fell out.

Let me know what you find.
Joe

You would need to get the vehicle up on a hoiste to inspect the pan for damage or like Joe mentioned before, a missing drain plug. The only way an oil pan will get damaged is if you actually ran over an object. If it were bad seals then the only time you would see the leak is when the vehicle is running. So since you say as soon as you added the oil it leaks right back out, you would see why the assumption would be a missing drain plug?