This reminds me of a very similar practice I encountered while consulting.
I am unclear on your role within this process though. You are obviously uncomfortable with the physician practice's conduct, but I'm not sure about your employment with the facility.
As for guidelines and the ethics here, we can pretty clearly establish that a.) this is an unethical practice and b.) it is antithetical to sound compliance practices. Outside that, there are probably several other conclusions we could draw, but I probably won't visit those.
Guidelines for physician services diagnostic coding are substantially different. If your job is to convince this practice of the opportunity for problem, simply pull a discharge summary where the patient is given a "probable" Principal Diagnosis. The physician claim for services on the day of discharge would also likely have that probable diagnosis coded as if it existed. Now extrapolate that to the length of time they've spent in doing this, by the number of patients treated annually and there's just a general figure on how many possible coding errors are out there.
If you work for the hospital supplying the coding abstracts, see what you can do about cutting them off. Those abstracts aren't coded for physician services use--they represent facility fee coding. The abstracts are really the administrative record of the hospital and therefore the hospital is under no obligation to disclose that.
In the event you'd happen to be on the payer side, promtply refer this case to a program integrity unit. The claims that the provider is submitting are not correct and some serious education should be done.
This isn't a case of physician coders using the hospital abstract, it's a case of a physician practice using the abstracts--if they had real coders on staff, this wouldn't be taking place!
Kevin B. Shields, RHIT, CPCO, CCS, CPC, COC, CCS-P, CPC-P, CPC-I