What intervention is appropriate for a patient with changes in stool caliper and constipation?

Ordering more testing is the appropriate intervention for a patient presenting with changes in stool caliber and constipation. These symptoms can indicate several underlying conditions, including possible obstruction, stricture, or malignancy, particularly of the colon. Additional diagnostic tests, such as imaging studies or colonoscopy, are essential to evaluate the gastrointestinal tract thoroughly and determine the cause of the symptoms.

This approach allows the healthcare provider to gather necessary information to establish an accurate diagnosis before initiating more invasive treatments or interventions. The other options may not be warranted at this stage without further investigation confirming a specific diagnosis. Consulting surgery or oncology would follow only if testing confirms a condition that warrants those referrals, and administering packed red blood cells is not relevant to addressing changes in stool caliber or constipation.