Stone Analysis


Sunquest Code:STONE  
Epic Code:LAB564Epic Name:Stone Analysis
Synonyms:Renal Calculi; Urinary Calculi; Calculus
Methodology:Reflectance Fourier Transform Infrared Spectrophotometry/polarizing microscopy
CPT Code:82365
Test Includes:Weight and composition
Turnaround Time:Specimens are sent to reference laboratory Mon-Sat; results are reported in 1-4 days.


Collection Instructions

Specimen:Calculi
Collection Instructions:Air-dry calculi and transport in an ARUP Standard Transport Tube. Larger calculi specimens may be transported in a plastic leakproof container.
Causes for Rejection:Calculi specimens transported in liquid or contaminated with blood require special handling to be processed. Blood and moisture interfere with this methodology. Samples that are wrapped in tape or embedded in wax will delay or prevent analysis and should not be submitted.


Processing and Shipping

Specimen Processing:See collection. Store at room temperature.
Shipping Instructions:Ship at room temperature.
Test Performed at or Referral Lab Lab Sendouts  (ARUP)
Referral Lab number:99460 (CALCULI)


Interpretive

Reference Range:By report.
Use:

 

Composition of Renal/Bile/Prostate Stones

Composition of Renal Stones

Substance

Frequency

Combined calcium oxalate and hydroxyapatite

70%

Magnesium ammonium phosphate hexahydrate and carbonate apatite

10%

Uric acid and urates

8%

Calcium oxalate

5%

Cystine

2%

Hydroxapatite

2%

Calcium monohydrogen phosphate dehydrate

1%

2,8-dihydroxyadenine

Rare

Oxypurinol and xanthine

Rare

Triamterene

Rare

Xanthine

Rare

Composition of Bile Stones

Cholesterol

Calcium bile salts

Carbonate

Some phosphate

Composition of Prostate Stones

Approximately 20% organic material

Inorganic component (chiefly carbonate apatite)

 

Calcium Oxalate: These stones account for 75% of all renal stones. The average age of onset is in the third decade. These stones have numerous causes; primarily hyperparathyroidism, idiopathic hypercalciuria, low urine citrate level, hyperoxaluria and hyperuricosuria.

 

Monohydrates vs. Dihydrates: Stones containing mostly calcium oxalate monohydrate form slowly and rarely recur. They are compact, have a smooth surface and pass spontaneously about half the time. Stones composed of calcium oxalate dehydrate form more quickly, recur frequently, have very rough surfaces, are brittle and usually require surgical removal.

 

Magnesium ammonium Phosphate Hexahydrate (Struvite): Struvite stones are commonly and potentially dangerous. These stones are formed mainly in men. Many patients who form uric acid stones have gout; the rest have some condition that results in isohydruria (fixed low urine pH) or hyperuricosuria.

 

Cystine: Cystine stones are very uncommon and are the result of an autosomal recessive trait (cystinuria or cystinosis) that causes defective renal tubular and intestinal transport of the amino acid cystine.

 

Calcium Monohydrogen Phosphate Dihydrate: Some researchers claim that all calcium phosphate stones are related to renal tubular acidosis. These patients often present with a very low citrate level and pH greater than 6.5.

 

Drug Metabolites:  While sulfonamides, trimterene and xanthine are not typical urinary calculi, with low fluid volume, these metabolites can precipitate and form stones.

 



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