Final answer:
The highest priority nursing intervention for a client with Crohn's disease who has developed a fistula is to C) encourage a high-protein and high-calorie diet to promote healing and prevent malnutrition.
Step-by-step explanation:
The highest priority nursing intervention for a client with Crohn's disease who has developed a fistula is C) Encourage the client to consume a diet high in protein and calories.
Fistulas are abnormal connections between two parts inside the body, which can cause the diversion of nutrients and lead to malnutrition.
Ensuring the client consumes enough protein and calories is crucial for healing and maintaining tissue integrity.
Positioning the client to allow gravity drainage of the fistula (A) is also important, but not the highest priority.
Monitoring blood glucose levels (B) and tracking hematocrit and hemoglobin (D) are important for overall patient monitoring, but they do not address the immediate needs presented by the fistula.