Updated: 10/10/2016

Renal Osteodystrophy

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https://upload.orthobullets.com/topic/9030/images/renal od histo.jpg
https://upload.orthobullets.com/topic/9030/images/renal od patho frac.jpg
https://upload.orthobullets.com/topic/9030/images/looser zones.jpg
https://upload.orthobullets.com/topic/9030/images/looserzone2.jpg
https://upload.orthobullets.com/topic/9030/images/brown.jpg
https://upload.orthobullets.com/topic/9030/images/sclerosis.jpg
Introduction
  • Definition
    • a spectrum of disease seen in patients with chronic renal disease.
    • characterized by bone mineralization deficiency due to electrolyte and endocrine abnormalities 
    • common cause of hypocalcemia
  • 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 post
        • carpalpedal spasm after blood pressure readings
      • Chvostek's Sign post
        • 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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Questions (5)

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

QID: 4397
1

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

57%

(2353/4128)

2

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

19%

(772/4128)

3

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

8%

(344/4128)

4

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

4%

(165/4128)

5

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

10%

(429/4128)

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?
Tested Concept

QID: 500
1

Decreased PTH secretion, hypophosphatemia, and hypocalcemia

4%

(70/1593)

2

Increased PTH secretion, hyperphosphatemia, and hypocalcemia

71%

(1127/1593)

3

Decreased PTH secretion, hypophosphatemia, and hypercalcemia

6%

(100/1593)

4

Increased PTH secretion, hyperphosphatemia, and hypercalcemia

14%

(220/1593)

5

Hypophosphatemia and hypocalcemia

4%

(69/1593)

L 2 C

Select Answer to see Preferred Response

(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? Tested Concept

QID: 683
1

Altered parathyoid hormone receptor sensitivity

26%

(450/1714)

2

Chronic metabolic alkalosis

4%

(62/1714)

3

Chronic imbalance of electrolytes during dialysis

4%

(71/1714)

4

Uremia related phosphate retention

60%

(1035/1714)

5

Tyrosine kinase receptor phosphorylation of the improper intracellular signalling proteins

5%

(88/1714)

L 3 C

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