Final answer:
In chronic PAD, the presence of collaterals is abnormal as they indicate an underlying disease and restricted blood flow.
Step-by-step explanation:
In chronic peripheral artery disease (PAD), the presence of collaterals is abnormal. Collaterals are alternative blood vessels that develop over time to bypass narrowed or blocked arteries and enhance blood flow. In chronic PAD, the narrowing of the arteries restricts blood flow to the affected area, leading to the development of collaterals as a compensatory mechanism. Therefore, the presence of collaterals indicates an abnormality in the arterial system due to the underlying disease.