For extensive laparoscopic endometriosis cases, I would code 58662-22. I realize in the most extreme endometriosis situations, this may undervalue the amount of work actually being performed. In my practice, this is not something we are doing often. If you are using an unlisted for those extreme situations, what value are you assigning to the unlisted code? In my experience, unlisted codes can and do get paid, but often require a lot of additional legwork, calls, letters and time.
1) When submitting unlisted, you should indicate in your code line what is being performed. The claim should also indicate a comparison code that is most similar to the amount of work for which you are requesting the payment for.
2) Be prepared for a request for additional information. When that comes, respond with the operative report and a letter. I word my letter for non-clinical staff, but include enough clinical details to explain what was performed and why the work is most similar to the comparison code you are requesting. If you often use an unlisted code for a specific procedure, you can simply create a template and just type in a unique sentence or 2 about this specific case.
3) Be prepared to send the information again. And perhaps again.
I personally use unlisted when there is no reasonable alternative. From the laparoscopic endometriosis cases I have seen, 58662-22 is reasonable and the most accurate coding.