Hi. I had the same questions as you about a discogram. It's not a nice test and the medicinal pics on the web do not explain it like experiencing it to be honest. It's not a nice test and one the docs dont enjoy doing, but can truly tell the tale if a disc is truly causing a patient pain or not.
The patient may or may not be lightly sedated (depending on the doctors preference). Needles are placed into bad discs and also a healthy one. Once the needles are placed, contrast dye is pushed into the discs and are therefore pressurized. If pain is generated and like the pain the patient normally experiences but is greatly emphasized, it is said to be a positive test at that level. Then they test a good disc to see if it causes the patient any pain as well. If no pain is generated, this is a good thing, as it shows that the patient isnt hurting everywhere, but at the "bad" discs only.
I had no sedation. It was immensely painful. Very very painful, but it was worth the amount of time I was hurting to find the true source of my pain that went undetected for over three years. I had a blown disc that looked normal on MRIs but when dye was injected into it, it just splattered out the backside of it as quickly as he injected it.
So while it was so painful, I would undergo this test again if needed.
I hope this helps you some, and that I also gave you some positives about this test.
