duplex exams with other ultrasounds

Can someone offer some clear guidance of coding duplex exams with other ultrasounds? For example ? If a patient has a transvaginal ultrasound and spectrum analysis and color flow is documented of the ovaries do you code a duplex exam? Or should there be separate orders and medical necessity to code the duplex?

The only information that I can locate is the below from the NCCI manual. Does this apply for any ultrasound?

The NCCI manual states- Abdominal ultrasound examinations (CPT codes 76700-76775) and abdominal duplex examinations (CPT codes 93975, 93976) are generally performed for different clinical scenarios although there are some instances where both types of procedures are medically reasonable and necessary. In the latter case, the abdominal ultrasound procedure CPT code should be reported with an NCCI-associated modifier.

duplex exams with other ultrasounds