Final answer:
The first action a nurse should take when a client with a urinary catheter reports lower abdominal discomfort is to check if the catheter is kinked, as this can cause discomfort by obstructing urine flow.
Step-by-step explanation:
When a client on bedrest with an indwelling urinary catheter reports discomfort in the lower abdomen, the first action by the nurse should be to check to see if the catheter is kinked. This is a basic troubleshooting step to ensure that urine flow is not obstructed, which could cause discomfort. If the catheter is not kinked and the discomfort persists, further assessment and interventions would be needed, potentially including obtaining a urine sample to test for a urinary tract infection (UTI) or considering catheter replacement under appropriate circumstances.