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Wednesday, 30 December 2020

LITHIASIS ON FOREIGN BODIES

Written by María Santamaría González | José Luis Bancalero Flores | Claudia Abadía Molina

Figure 1. Lithiasis on suture thread in a 79-year-old man. A) and B) Lithiasis on suture thread. C) Fragment: 55% whewellite, 40% weddellite and 5% hydroxyapatite. D) Infrared spectrum (IRS) of organic matter. E) IRS corresponding to whewellite, weddellite, and hydroxyapatite.

The main cause of lithogenesis is supersaturation of some constituents in urine. Other factors as extreme pH, anatomical malformations or presence of promoters can facilitate this process too.
Furthermore, certain etiopathogenic conditions like thepresence of an obstacle that slows down urinary flow can themselves induce urinary stone formation. In this sense, we review stones developed on a foreign body found in urinary tract (surgical sutures, staples, catheters, etc.). This article describes two cases of this type of lithiasis.

Because of various processes that urothelial cells undergo it may precipitate some mucoprotein. When they join forming macroaggregates, it is set up the organic matrix that act as an heterogeneous nucleant of calcium oxalate. These glycoproteins form the protein matrix that favors the precipitation of calcium salts.

Another protein found in most of urinary stones is albumin. It seems to act as a promoter by a quadruple mechanism: it adsorbs on different types of crystals, reduce Zeta potential facilitating irreversible adhesion, it joins ionic calcium and other proteins.

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Figure 2. Ureteral lithiasis on double J stent (DJS) traction thread in a 60-year-old man. A) Fragment: 62% phosphocarbonates and 7% struvite (nucleus), and 31% uric acid dihydrate (periphery). B), C) and D) Ureteral lithiasis on traction thread. E) IRS corresponding to struvite and phosphocarbonates. F) IRS corresponding to uric acid dihydrate.

Ureteral permeabilization with DJS provides benefits in certain pathologies, having indications for both prophylactic and therapeutic purposes. However, its placement is not exempt of risk. One of the most frequent is bacterial infection. Manipulation when placing it, the ureterovesical reflux or biofilms formation by urinary-tract bacteria are some factors that promoted infection.

Among the opportunistic germs that can infect DJS are urease-producing bacteria (Escherichia, Proteus, Klebsiella, Pseudomonas). They hydrolyze the urea into ammoniac and carbon dioxide increasing urinary pH. As a result, phosphate precipitation occurs. Then, it joins to ammonia and magnesium forming struvite, or phosphocarbonate if it joins calcium.

In conclusion, urinary stones study is essential to determine what caused them in first term. That in some cases may be the consequence of an invasive procedure performed as a need in the urological patient.

REFERENCES
  1. Lázaro Castillo, J. Aspectos médico-analíticos de la litiasis urinaria recidivante: bases etiopatogénias, diagnostico bioquímico, análisis de cálculos, tratamiento médico, atlas fotográfico. España: Izasa; 2010.
  2. García García MP, Luis Yanes MI. Litiasis renal. En: Lorenzo V, López Gómez JM (Eds.). Nefrología al Día. Barcelona: Elsevier España; 2018. 133-47. Disponible en: https://www.nefrologiaaldia.org/es-articulo-litiasis-242.
  3. Cepeda M, Mainez JA, de la Cruz B, Amón JH. Indicaciones y morbilidad asociada a los catéteres doble J.    Archivos Españoles de Urología 2016;69(8): 462-70.
  4. C. Türk, A. Skolarikos, A. Neisius, A. Petrik, C. Seitz, K. Thomas. European Association of Urology (EAU). EAU Guidelines. Urolithiasis. 2019. Disponible en: http://uroweb.org/guideline/urolithiasis


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