Lab Test

Stone Analysis

Calculi Analysis, Calculus Analysis, Kidney Stone Analysis, Renal Calculi, Urinary Calculi

Test Codes



Send Outs

Specimen Collection Criteria

Collect: Submit entire air-dried urinary calculi specimen in a sterile collection container.

  • Specimen source is required on request form for processing.
  • Do not tape the specimen to anything; tape interferes with the analytical procedure.
  • Do not send the stone in formalin.

Physician Office/Draw Specimen Preparation

Air dry specimen and store at room temperature (20-26°C or 68-78.8°F) prior to transport.

Preparation for Courier Transport

Transport: Air-dried specimen at room temperature (20-26°C or 68-78.8°F).

Rejection Criteria

Specimens other than renal stones.

Specimens not collected and processed as indicated.

In-Lab Processing

Air dry specimen and store at room temperature (20-26°C or 68-78.8°F) prior to transport.

Transport: Air-dried specimen at room temperature (20-26°C or 68-78.8°F).


Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): Indefinite
Refrigerated (2-8°C or 36-46°F): Indefinite
Frozen (-20°C/-4°F or below): Indefinite

Specimen Storage in Department Prior to Disposal:

Specimen retention time is determined by the policy of the reference laboratory. Contact the Send Outs Laboratory with any questions.


Sent to Mayo Medical Laboratories, Rochester, MN.


Monday – Saturday.
Results are available in 3-5 days.

Reference Range

By report.

Test Methodology

Infrared spectrum analysis.

Representative specimens are taken from all identifiable layers of the calculus. Each specimen is weighed and crushed into a fine powder. An infrared spectrum of each specimen is recorded and the resulting spectrum compared against reference spectra of all known calculus components. This procedure allows for accurate analyses of complex crystal mixtures as well as the hydration state of each crystal type.


Calcium oxalate stones:

  • Production of calcium oxalate stones consisting of oxalate dihydrate indicate that the stone is newly formed and current urine constituents can be used to assess the importance of supersaturation.
  • Production of calcium oxalate stones consisting of oxalate monohydrate indicate an old (greater than 2 months since formed) stone and current urine composition may not be meaningful.

Magnesium ammonium phosphatae stones (struvite):

  • Production of magnesium ammonium phosphate stones (Struvite) indicates that the cause of stone formation was infection.
  • Treatment of the infection is the only way to inhibit further stone formation.

Ephedrine/guaifenesin stones:

  • Certain herbal and over-the-counter preparations (e.g., Mah Jung) contain high levels of ephedrine and guaifenesin. Excessive consumption of these products can lead to the formation of ephedrine/guaifenesin stones.

Clinical Utility

Managing patients with recurrent renal calculi.

CPT Codes

LOINC:  40787-4


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