What is the correct way to bill an EGD w/bx and an ERCP when they are performed together?

The physician performed the EGD w/bx first using a gastroscope, then he withdrew the scope and passed the duodenscope to perform the ERCP.

Would you bill an ERCP and EGD w/bx or just an ERCP w/bx? How do you bill for these procedures when performed together?