Thursday, 30 April 2020


Written by Ana María García Cano | Alejandro José Ravelo Marrero | Alba Arroyo Vega

Figure 1. Set of kidney stones of the same patient (a), examined individually according to their appearance (b, c and d). Typical calcium oxalate monohydrate kidney stone (e). Several kidney stones of 388.5 mg corresponding to the same patient (a). Depending on their appearance three kidney stones are distinguised: the first is brown, smooth, rounded surface and hard fracture consistency (b). The second is light brown, smooth, rounded surface and hard fracture consistency (c). The third is grayish, with a rough surface, and intermediate hardness (d).

Kidney stones belong to a 54-year-old patient with surgical history of multiple renal lithiasis, who presents an episode of left obstructive uropathy with infection due to a new event of lithiasis. She required a double J stent placement.
A computed tomography of abdomen and pelvis scan shows multiple lithiasis in the left kidney and ureter characterized by high density (12,000 UH) and radiopacity.

After several months, the catheter is removed and the patient undergoes surgical treatment. The high density of the different fragments contraindicates lithotripsy, therefore, retrograde intrarenal surgery is performed with stone fragmentation by laser and extraction.

The composition of the stones is analyzed in the laboratory by infrared spectroscopy (IR) after sample preparation. To this effect, the calculus is fractured in an agate mortar to get an aliquot which is scattered and mixed with potassium bromide (KBr). The mixture is compacted in a hydraulic press obtaining a 1 mm thick tablet which is studied in the IR spectroscope.

The spectra show a common composition in all fragments, in this case calcium oxalate monohydrate (COM) with calcium phosphate (CF) (Figure 2). In Figure 1b and c, the stone surface is composed of COM with a CF core. In Figure 1d, COM locates in the core and CF at surface.

imagen2Figure 2. IR spectrum obtained from the analysis of the patient's kidney stones showing predominant composition of COM with traces of CF.

The appearance of lithiasic fragments are unusual for their superficial pearl luster and colour, highlighting even different shades of colour (figures 1b and c) and in some cases located in the core (figure 1d). COM calculi generally have dark brown colour, with spherical, mammillary surface and hard consistency to fracture (figure 1e).

There are two types of COM kidney stones: papillary and cavitary. The first one forms on lesions of the renal papilla. The cavitary COM stone does not join this structure and requires cavities with low urodynamic efficiency to form. The long-term urinary catheterization in the patient favored urine pooling and sticking of heterogeneous organic matter. As a result she developed cavitary COM stones.

The importance of correct characterization allows physicians to adopt dietary and pharmacological measures to prevent recurrences in the future.


  1. Daudon M, Dessombz A. Comprehensive morpho-constitutional analysis of urinary stones improves etiological diagnosis and therapeutic strategy of nephrolithiasis. Comptes Rendus Chimie. 2019;19(11-12):1470-1491.
  2. European Association of Urology. EAU Guidelines on Urolithiasis 2018. Arnhem, The Netherlands. EAU Guidelines Office; 2018.
  3. Ávila Padilla S, editor. Litiasis Práctica. Madrid: Unidad de Imagen del Hospital Ramón y Cajal; 2003.
  4. E. Pieras Ayala, F. Grases Freixedas, A. Costa Bauzá et al. Litiasis de oxalato cálcico monohidrato papilar y de cavidad: estudio comparativo de factores etiológicos. Arch. Esp. Urol. 2006; 59, 2 (147-154).


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