Final answer:
The first-listed diagnosis for this encounter would be elevated blood pressure, also known as hypertension.
Step-by-step explanation:
The first-listed diagnosis for this encounter would be elevated blood pressure, also known as hypertension. In this scenario, the patient's colonoscopy was not performed due to her elevated blood pressure. An elevated blood pressure is a significant medical condition that needs to be addressed and managed before any surgical procedure can take place.