Final answer:
The nurse should instruct the patient to produce at least 2,000 mL of urine each day to prevent the formation of renal calculi and promote waste excretion.
Step-by-step explanation:
The nurse should instruct the patient to increase fluid intake to a level where the patient produces at least 2,000 mL of urine each day. The normal range of urine volume is one to two liters per day, with a minimum urine production of about 500 mL/day to rid the body of wastes. Increasing fluid intake helps prevent the formation of renal calculi and promotes the excretion of metabolic wastes from the body.