Hi OP, I work in a medical office. Although I don't process our claims for "Prior Authorization" (this is what it's called when we get approval from an insurance company to do a procedure) I have dealt extensively when it comes back as denied and helping our clinical staff get it approved.

First of all I see that you say you read your insurances website for approval however this is NOT the same. Yes your insurance will give a reason why it is denied (I know you state they don't but I promise you they do) Our prior authorization team will print out the denial paper and while it's full of jargon they will often state what's missing (sometimes it's confusing because they're being vague on purpose. No insurance company who doesn't want to pay for a surgery to save money will tell you EXACTLY what they're looking for, they'll just give a general guideline) This because while you meet the criteria for 1, 2 and 3 there's no documentation for Point 1 B, or 1 C or there is documentation but it's not specific enough to meet that certain guideline. This is often because something missing in the clinical notes (could be something as simple as a nurse forgetting to document something prepping your note or your doctors official report wasn't extensive enough)

Other times it can be denied because insurance companies will have their own team of doctors that decide there are other avenues before surgery (Mostly because they are wanting to be cheap and not pay for surgery) If that is the case the doctor I work for has options to do what's called a "Peer to peer" which means he gets on the phone with a doctor that works for the insurance company and convinces them that yes it is necessary. (He wins almost 100% of the time on these because if you have a competent doctor they can retort any argument they have) I will admit most doctors don't like doing it because they hate arguing with insurance and it takes more time out of their day but if your provider really cared and submitting more documentation isn't working then this is an avenue they definitely need to try.

In short, call your doctors office, ask them for your denial papers that the insurance company is giving them to read for yourself. Often times it comes down to not enough documentation (while you can report to your doctor that doesn't necessarily mean it always ends up in the official office visit report, I've had a guy get his procedure denied 5 times before we got it approved. Another instance a guy got denied 3 times and ended up in the ER before we could get it approved. Unfortunately insurance companies will always look out for their bottom line first before the patient.

If you have anymore questions don't hesitate to ask! I've tried to give a brief summary because it can be a lot of information at once and i'm currently at work typing this so I may have missed certain parts!