Colonoscopy on HDHP. Best option

So here is my dilemma. Today is the last day for benefits signup. I have an appt at John Hopkins coming up at the end of this year for gastrointestinal issues that have not be identified. I know from others who have went, John Hopkins is likely going to require me to get a colonoscopy. I am 43 years old, and given this isn’t a preventative procedure, I am assuming insurance (Aetna) will be billing me as a diagnostic procedure.

We have never been on a HDHP but aside from this instance, our medical bills have been minimal which is why we were going to opt to try this out. However, I’m now fearful we will be required to meet the out of pocket max which is $8,000.00 as opposed to the $4,000.00 on our current PPO. Is there anything I can do to avoid this? I know it seems to come down to how the hospital codes it but I don’t know that I want to take the risk. Seems like given I know I am going to have this procedure, we should stick with the PPO for this year. Any advice would be greatly appreciated!

PS We would be saving ~$2200.00 in premiums with the HDHP and the employer also contributes $1,000.00 for the year. If my simple math is right, the difference between both plans with this procedure would be us paying an additional $800.00 out of pocket in comparison to the PPO. (the 2200 in savings from premiums we would just be contributing into the HSA)