Could you still have Interstitial Cystitis and have a normal cystoscopy?

I've had abdominal pain for a long time now. I have a history of kidney stones, have had surgery to determine if I had endometriosis. Today, I had a cystoscope and the Urologist said that the inside of my bladder looked good. I frequently have blood in my urine and can always tell if its a kidney stone or not. This abdominal pain feels nothing like kidney stones. They found a large, inflamed mass on the outside of my colon. The OBGYN thought it was an inflamed diverticulum but I had a colonoscopy and he said that it was not diverticulitis. At this point, they don't know what the mass is and have made a decision that it needs to come out. They said they needed to know what it was or what it could be. During a pelvic exam, the OBGYN felt around and told me to tell him if, when, and where my pain could be felt during the exam. He felt around and I jumped back because I felt a horrible pain. He said that it was the bladder that he had been touching. He said that he thought it was Interstitial Cystitis, the Urologist said that the cystoscope in the bladder was normal. I read online that even if a cystoscopy shows no abnormalitites, it doesn't mean that it isn't interstitial cystitis. Its hard to diagnose because sometimes all you feel is pain in the bladder. I'm just curious if that's true. Could it still be interstitial cystitis even with a normal cystoscope and a normal cystogram? Any ideas?