It seems that Aetna strictly adheres to Medical Necessity concepts in some contexts, and this is an example. I would like to give an example and by my observation Aetna's policy matches that of ACOG findings in this regard, the underlying concept is "Medical Necessity".
The majority of the physicians on ACOGs coding committee believe that there is only a small physician work component involved in doing both views. Most of the cost is involved in the use of an additional transducer, which is part of the technical component, not the professional component. In most cases, the committee believes that starting the ultrasound abdominally and then scanning vaginally is doing more work than may be necessary in most cases. Some of the committee members believe that you should always start with a transvaginal view and only if the structures in question cannot be seen properly would you do an abdominal or pelvic scan.
An old ACOG Technical Bulletin also suggests starting with the transvaginal method, then opting for the abdominal procedure only if necessary:
The decision of which modality to use first depends on the clinical entity suspected as a result of the physical examination. In many instances, transvaginal ultrasonography is performed and, if it is inconclusive, a transabdominal examination is required.
Many insurances agree follow ACOG opinion that the insurer is looking for an explanation of why both procedures were performed. You have to say why you are doing two ultrasounds, says Witt. Proof must be provided that both procedures were medically necessary to get the full picture.
An eminent author also gave the example of an extremely overweight patient having an ultrasound. Her body density would dictate that both views were needed to get a complete picture of the pelvic region. Likewise, a patient with very dense adhesions might require two views. Documenting this to the insurance company will help ensure a reimbursement.