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calcium stone

75-85% of all renal stones contain calcium. Etiology: 1) hypercalciuria a) idiopathic b) renal tubular acidosis (RTA) type 1 (calcium phosphate) - topiramate 2) hyperoxaluria a) calcium oxalate b) patients must have an intact colon to absorb oxalate c) free oxalate is increased by free fatty acids competing for Ca+2 & Mg+2, usual binders of oxalate d) fatty acid & bile salts increase permeability to oxalate - orlistat inhibits absorption of fatty acids & bile salts & increases risk of hyperoxaluria e) factors increasing hyperoxaluria 1] decreased water absorption 2] decreased bicarbonate absorption 3] decreased absorption of inhibitors f) recessive disorder in oxalate metabolism g) inflammatory bowel disease h) roux-en-Y gastric bypass surgery [5] 3) reduced inhibitor excretion a) Mg+2 b) pyrophosphates c) citrate (RTA-1) 4) primary hyperparathyroidism 5) sarcoidosis Epidemiology: - most common in 3rd to 5th decade of life Pathology: 1) 1,25-dihydroxyvitamin D3 levels may be increased 2) inappropriate calciuria may occur with calcium-restricted diets 3) calcium oxalate stones form in acidic urine 4) calcium phosphate stones form in alkaline urine Laboratory: 1) serum PTH 2) renal function tests 3) urinalysis & culture - urine microscopy - calcium oxalate crystals in urine - calcium phosphate crystals in urine 4) 24 hour urine: a) hypercalciuria: > 300 mg (men) or 250 mg (women) or > 4 mg/kg in 24 hours b) creatinine c) uric acid 5) 24 hour urine volume 6) serum Ca+2 is generally normal 7) stone analysis: composition: a) calcium oxalate & calcium phosphate a) rarely, pure calcium phosphate Management: 1) correcting dietary stresses a) Na+ increases urinary Ca+2 -> diet of < 3 g of salt/day [4] b) animal protein increases urinary Ca+2 -> diet of < 8 oz of meat/day [4] 2) increasing urine volume > 2.5L/day 3) thiazide diuretics for hypercalciuria a) Na+ must be restricted for urine Ca+2 to decrease by 50% b) development of hypercalcemia suggests latent hyperparathyroidism c) amiloride may also be of benefit 4) bicarbonate* for patients with type 1 RTA 5) allopurinol for patients with hyperuricosuria 6) patients with primary hyperparathyroidism & urolithiasis - removal of parathyroid adenoma 7) reduce intestinal absorption of oxalate a) increase dietary calcium, decrease dietary oxalate & fat may reduce intestinal absorption as oxalate [3,4] b) calcium citrate (Citracal) may be best form [4] c) cholestyramine to bind bile acids (enteric hyperoxaluria) 8) replacement of inhibitor substances a) potassium citrate b) pyrophosphate c) magnesium oxide

Related

calcium oxalate (CaC2O4) calcium oxalate crystals in urine calcium phosphate (Ca3[PO4]2) calcium phosphate crystals in urine

Specific

calcium oxalate stone calcium phosphate stone

General

urinary calculus (stone, nephrolithiasis, urolithiasis)

References

  1. Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 615
  2. Medical Knowledge Self Assessment Program (MKSAP) 11, 16, 17. American College of Physicians, Philadelphia 1998, 2012, 2015
  3. Journal Watch 22(3):20, 2002 Borghi et al, N Engl J Med 346:77, 2002
  4. Prescriber's Letter 9(3):18 2002
  5. Maalouf NM, Tondapu P, Guth ES, Livingston EH, Sakhaee K. Hypocitraturia and hyperoxaluria after Roux-en-Y gastric bypass surgery. J Urol. 2010 Mar;183(3):1026-30. PMID: 20096421
  6. NEJM Knowledge+ Nephrology/Urology
  7. Worcester EM, Coe FL. Clinical practice. Calcium kidney stones. N Engl J Med. 2010 Sep 2;363(10):954-63. PMID: 20818905 PMCID: PMC3192488 Free PMC article. Review. https://www.nejm.org/doi/pdf/10.1056/NEJMcp1001011