A 68-year-old woman with stage 4 chronic kidney disease (CKD) presents to the clinic reporting fatigue, shortness of breath on exertion, and pallor. Her laboratory results show hemoglobin 8.2 g/dL, hematocrit 25%, serum ferritin 180 ng/mL, and transferrin saturation 18%. She denies blood in her stool and has no history of dietary iron deficiency. Which pathophysiologic mechanism most directly explains this client's anemia?
- Decreased erythropoietin production by the diseased kidneys
- Nutritional iron deficiency due to restricted dietary intake
- Chronic gastrointestinal blood loss from uremic gastritis
- Hemolysis of red blood cells caused by circulating uremic toxins