Name two major CKD complications and their pathophysiology.

• A. Hypokalemia from increased excretion; hyponatremia from impaired water clearance.
• B. Hyperphosphatemia with secondary hyperparathyroidism causing bone disease.
• C. Anemia from reduced erythropoietin production; hyperphosphatemia with secondary hyperparathyroidism causing bone disease.
• D. Hypernatremia from water loss; hypocalcemia from calcification.

Answer: (C)

The main concept is that chronic kidney disease leads to two major problems: anemia from reduced erythropoietin production, and a mineral-bone disorder from impaired phosphate handling and vitamin D activation.

In CKD, damaged kidneys produce less erythropoietin, the hormone that drives red blood cell production. With less EPO, the bone marrow makes fewer red cells, causing a normocytic, normochromic anemia and symptoms like fatigue. This is a direct consequence of the kidney’s diminished endocrine function.

At the same time, the diseased kidneys can’t excrete phosphate effectively, so phosphate accumulates. They also fail to activate vitamin D, reducing calcium absorption from the gut. The combination of high phosphate and low calcium stimulates the parathyroid glands to release more PTH (secondary hyperparathyroidism). Chronic elevation of PTH increases bone turnover and resorption, leading to renal osteodystrophy, a bone disease common in CKD.

So the best answer pairs anemia due to lack of erythropoietin with hyperphosphatemia-driven secondary hyperparathyroidism causing bone disease, which are two hallmark CKD complications explained by how kidney dysfunction alters EPO production and mineral metabolism.