Bone and Mineral Metabolism in CKD (CKD-MBD) Flashcards

What term describes the systemic disorder in CKD encompassing abnormalities of calcium, phosphorus, PTH, and vitamin D metabolism along with bone disease and vascular calcification?

Answer: CKD-Mineral and Bone Disorder (CKD-MBD)

KDIGO coined the term CKD-MBD in 2006 to describe the broader systemic syndrome linking biochemical abnormalities, bone disease (renal osteodystrophy), and vascular/soft-tissue calcification in CKD.

Which laboratory value is the BEST indicator of nutritional (storage) vitamin D status in a CKD patient, and should be checked before starting supplementation?

Answer: Serum 25-hydroxyvitamin D (calcidiol) level

Serum 25-hydroxyvitamin D (calcidiol) reflects hepatic storage and substrate availability for both renal and extrarenal activation, making it the standard measure of vitamin D nutritional status in all patients including those with CKD.

A CKD G4 patient develops vascular calcification on imaging. Which phosphate management strategy is MOST appropriate according to current guidelines?

Answer: Prioritize dietary phosphorus restriction and use calcium-free phosphate binders when needed

In CKD patients with vascular calcification, calcium-based binders should be avoided or minimized to prevent additional calcium loading; calcium-free binders (sevelamer, lanthanum) are preferred alongside dietary phosphorus restriction.

Tertiary hyperparathyroidism most commonly develops in which clinical scenario?

Answer: After kidney transplantation when autonomous parathyroid hyperplasia persists despite restored renal function

Tertiary hyperparathyroidism describes autonomous, unregulated PTH hypersecretion from hyperplastic parathyroid glands that persist after transplantation, often causing hypercalcemia and hypophosphatemia in the post-transplant period.

Klotho, a co-receptor for FGF-23, declines progressively in CKD. What is the PRIMARY consequence of reduced Klotho expression?

Answer: Impaired FGF-23 signaling leading to phosphate retention and decreased calcitriol synthesis

Klotho deficiency in CKD blunts the kidney's response to FGF-23 (phosphaturic signal), contributing to phosphate retention; it also independently suppresses 1-alpha hydroxylase, further reducing calcitriol and worsening CKD-MBD.

A renal dietitian counsels a hemodialysis patient on the 'phosphorus protein ratio' approach. Which combination BEST represents a high-phosphorus-to-protein ratio food to LIMIT?

Answer: Processed cheese and cola beverages

Processed cheese is loaded with inorganic phosphate emulsifier additives, and cola beverages contain phosphoric acid — both have very high bioavailable phosphorus relative to their protein content, making them priority foods to restrict.

Per KDIGO 2017 recommendations, what is the suggested upper limit for total elemental calcium intake (diet plus supplements) in most adult CKD patients to reduce the risk of hypercalcemia and vascular calcification?

Answer: 2,000 mg/day

KDIGO and NKF/KDOQI guidelines recommend limiting total elemental calcium from all sources (diet and supplements) to no more than 2,000 mg/day, with lower limits (≤1,500 mg/day) often recommended when calcium-based binders are used.