Final answer:
Severe pain unrelieved by elevation is a manifestation of compartment syndrome in a client with a short leg cast.
Step-by-step explanation:
The nurse should identify severe pain unrelieved by elevation as a manifestation of compartment syndrome in a client with a short leg cast. Compartment syndrome occurs when there is increased pressure within a confined space, such as a muscle compartment, leading to decreased blood flow and tissue damage. The severe, unrelieved pain is due to the compression of nerves and blood vessels in the affected area.