Monday, 30 December 2019


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Written by María Santamaría González | Paula Sienes Bailo | José Luis Bancalero Flores

Figure 1. Multiple kidney stones composed of calcite from a 64-year-old man subjected to lithotripsy. The structure is described as granuloporous, concentric in the nucleus and the trigonal system crystallization. Its composition is 90% calcite, 10% calcium oxalate monohydrate. In the lower, the infrared spectrum of the stone is shown, and at right, the effervescence when it reacts with 0.2M HCl, generating bubbles of CO2 can be observed.
Calcite is the mineral name of Calcium Carbonate (CaCO3), a special form of crystallization is known as Aragonite. It constitutes an own crystalline archetype that can form pure or mixed calculi. Despite this, it is hardly reflected in the classifications of the crystalline species which can be found in human urinary lithiasis due to its unusual appearance. In fact, calcium carbonate urinary stones are currrently exceptional and their production is associated with the chronic elimination of gastric alkalizing pharmacological products (currently they are rarely used), or as a consequence of extreme malnutrition. In contrast, calcium carbonate is relatively common in biliary lithiasis.

The two varieties of calcium carbonate, previosly descrited, react by emitting CO2 due to the addition of hydrochloric acid. They could be differenced by the aspect, the crystallization and infrared spectrum absorption:

  •  he Calcite looks marble but is soft. It crystallizes in a piramidal system and is characterized by presenting bands at 2500, 1700-1300, 875 y 690 cm-1.
  • The Aragonite is firm when cut it. It is usually white but it also might be purple, brown, black, blue or green. It crystallizes in orthorhombic system and it is outlined by its wide absorption band between 1600-1400 and another with 875 cm-1.
The morfologic study was done by the cut and the inspection of the fragments by microscope. The composition was determinated by infrared spectroscopy (IRAffinity-1S).


Figure 2. Kidney stone of aragonite expelled spontaneously in a 72-year-old woman. In the laboratory examination, the structure is described as granuloporous and the crystallization is detailed as a case of orthorhombic system. Its composition is 80% aragonite, 18% phosphocarbonate, 2% calcium oxalate dihydrate. In the lower, the infrared spectrum of the calculus is shown, and at right, the reaction of CO2 production can be observed.
Infrared spectroscopy is a specific and precise method for the identification of the chemical composition of kidney stones. It uses the absorption bands in the IR range of the electromagnetic spectrum. The main advantage of this method is the speed ofanalysis, besides it can make a distinction between the absorption bands may correspond to a pure or a mixture of compounds, so knowledge of the IR technique and the experience of specialized is fundamental for a correct analysis.

A complementary technique to detect the mineral origin of carbonate is the diffraction of the X-rays, but the complexity and cost of the instruments prevent their application in the usual clinical practice.

Finally, as the calculi is the last product of a multifactorial process, the analysis of its mineral composition allows us to identify the determining factors of its formation and obtain a predictive value of the underlying metabolic abnormalities, as well as the different hygienic-dietetic measures or pharmacological treatments to reduce the high risk of recurrence associated with this pathology.

  1. European Association of Urology (EAU). EAU Guidelines. Urolithiasis. 2019. Disponible en:
  2. Khan AH, Imran S, Talati J, Jafri L . Fourier transform infrared spectroscopy for analysis of kidney stones. Investig Clin Urol. 2018;59(1):32-37
  3. Lázaro Castillo, J. Aspectos médico-analíticos de la litiasis urinaria recidivante: bases etiopatogénicas, diagnóstico bioquímico, análisis de cálculos, tratamiento médico, atlas fotográfico. España: Izasa; 2010.
  4. Sánchez-Martín FM, Arzoz Fàbregas M, Pieras Ayala E, Budía Alba A. Experto Universitario en urolitiasis. España: Editorial médica Panamericana; 2018.
  5. Yuzawa M, Nakano K, Kumamaru T, Nukui A, Ikeda H, Suzuki K, Kobayashi M, Sugaya Y, Morita T. Does carbonate originate from carbonate-calcium crystal component of the human urinary calculus? Nihon Hinyokika Gakkai Zasshi. 2008;99(6):681-7


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