A 60-year-old woman comes in for her annual physical. Even though she usually has a lot of energy, she has been unusually tired for the past few weeks. She occasionally feels dizzy and she is finding it harder to sleep through the night. Her ankles and feet are swollen and her face looks a bit puffy. She frequently feels a burning pain in her lower back, just below the rib cage. She has noticed that her urine is darker in color lately. Preliminary workup shows she has elevated blood pressure. Some red blood cells are present in her urine.