Updated: 6/17/2021

Renal Osteodystrophy

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  • summary
    • Renal Osteodystrophy is a form of metabolic bone disease seen in patients with chronic renal insufficiency characterized by bone mineralization deficiency due to electrolyte and endocrine abnormalities. Patients present with osteomalacia, osteonecrosis and pathologic fractures. 
    • Diagnosis is made based on a thorough evaluation of serum labs, clinical features, and radiographic findings.
    • Treatment involves medical management to resolve the etiology of the underlying renal condition.
  • Etiology
    • Pathophysiology
      • hypocalcemia
        • due to the inability of the damaged kidney to convert vitamin D3 to calcitrol (the active form)
        • because of phosphate retention (hyperphosphatemia)
      • hyperparathyroidism and secondary hyperphosphatemia
        • caused by hypocalcemia and lack of phosphate excretion by damaged kidney
      • uremia related phosphate retention
        • is a key pathological step
    • Associated conditions
      • orthopaedic manifestations
        • osteomalacia (adults) and growth retardation (children)
        • AVN
        • tendinitis and tendon rupture
        • carpal tunnel syndrome
          • deposition of amyloid (β2 microglobulin)
        • pathologic fracture
          • from brown tumors (hyperparathyroidism) or amyloid deposits
        • osteomyelitis and septic arthritis
  • Classification
    • High-turnover renal bone disease (high PTH disease)
      • chronically elevated phosphate leads to secondary hyperparathyroidism
        • hyperphosphatemia lowers serum Ca, stimulating PTH
        • phosphorus impairs renal 1α-hydroxylase, reducing 1,25(OH)2 vitamin D3 production
        • phosphorus retention directly stimultes PTH production
        • hyperplasia of chief cells of parathyroid gland
      • associated lab values
        • decreased calcium, increased serum phosphate, increased alkaline phosphate, increased parathyroid hormone
    • Low turnover renal bone disease (normal PTH disease)
      • characterized by lack of secondary hyperparathyroidism
      • normal levels of PTH with characteristic bone lesions marked by low levels of bone formation
      • excess deposition of aluminium into bone affects bone mineralization
        • impairs differentiation of precursors into osteoblasts, and osteoblast proliferation
        • impairs PTH release from parathyroid gland
        • disrupts mineralization
  • Presentation
    • Symptom
      • weakness
      • bone pain
      • pathological fracture
        • commonest complication
      • skeletal deformity
      • symptoms of hypocalcemia
        • abdominal pain
        • muscle cramps
        • dyspnea
        • convulsions/seizures
        • mental status changes
    • Physical exam
      • provocative tests for tetany
        • Trousseau's Sign
          • carpalpedal spasm after blood pressure readings
        • Chvostek's Sign
          • facial muscle contractions after tapping on the facial nerve
  • Imaging
    • Radiographs
      • findings
        • Looser's zones
        • brown tumor
        • osteosclerosis
          • from mineralization of osteomalacic bone
          • rugger jersey spine
        • widened growth plate and zone of provisional calcification (children)
        • varus deformity of the femurs (children)
        • fracture
        • soft-tissue calcification
        • osteopenia
    • CT
      • osseous resorption
  • Evaluation
    • Histology
      • thinned trabeculae
      • amyloid stains pink on Congo red stain
    • Labs
      • decreased serum calcium
      • increased serum phos
      • increased PTH
  • Treatment
    • Nonoperative
      • treat underlying renal condition or relieve urologic obstruction

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Flashcards (2)
Cards
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Questions (5)

(OBQ12.37) Which of the following series of lab values is most consistent with a diagnosis of high turnover renal osteodystrophy?

QID: 4397
1

Decreased calcium, increased serum phosphate, increased alkaline phosphatase, increased parathyroid hormone

57%

(2412/4237)

2

Decreased calcium, decreased serum phosphate, increased alkaline phosphatase, increased parathyroid hormone

19%

(796/4237)

3

Increased calcium, normal serum phosphate, increased alkaline phosphatase, normal parathyroid hormone

8%

(351/4237)

4

Decreased calcium, increased serum phosphate, normal alkaline phosphatase, decreased parathyroid hormone

4%

(170/4237)

5

Increased calcium, normal serum phosphate, normal or high alkaline phosphatase, increased parathyroid hormone

10%

(443/4237)

L 4 B

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(OBQ08.114) What laboratory findings would you expect to find in a patient newly diagnosed with renal osteodystrophy?

QID: 500
1

Decreased PTH secretion, hypophosphatemia, and hypocalcemia

4%

(74/1685)

2

Increased PTH secretion, hyperphosphatemia, and hypocalcemia

71%

(1191/1685)

3

Decreased PTH secretion, hypophosphatemia, and hypercalcemia

6%

(105/1685)

4

Increased PTH secretion, hyperphosphatemia, and hypercalcemia

14%

(237/1685)

5

Hypophosphatemia and hypocalcemia

4%

(71/1685)

L 2 C

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(OBQ07.22) You are seeing a dialysis patient for a fragility fracture. This patient also carries a diagnosis of renal osteodystrophy. What is the key pathophysiological step that is responsible for his osteomalacia?

QID: 683
1

Altered parathyoid hormone receptor sensitivity

26%

(471/1808)

2

Chronic metabolic alkalosis

4%

(66/1808)

3

Chronic imbalance of electrolytes during dialysis

4%

(75/1808)

4

Uremia related phosphate retention

60%

(1087/1808)

5

Tyrosine kinase receptor phosphorylation of the improper intracellular signalling proteins

5%

(99/1808)

L 3 D

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Evidence (3)
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