Final answer:
For a 7-year-old with acute glomerulonephritis and hematuria, bed rest is the most appropriate intervention to aid healing and reduce symptoms.
Step-by-step explanation:
The most appropriate nursing intervention for a 7-year-old with acute glomerulonephritis experiencing gross hematuria would likely be to encourage bed rest. This recommendation helps decrease the body's metabolic demands and renal perfusion, potentially reducing the severity of symptoms and promoting healing. While administering diuretics, restricting fluid intake, and applying cold compresses to the perineum might be appropriate for other conditions, these interventions are not the primary choice for a child with acute glomerulonephritis and gross hematuria.