, Volume 41, Issue 6, pp 481–486 | Cite as

Stent encrustation in feline and human artificial urine: does the low molecular weight composition account for the difference?

  • M. Shafat
  • K. Rajakumar
  • H. Syme
  • N. BuchholzEmail author
  • M. M. Knight
Original Paper


Anecdotal evidence suggests that the rate of encrustation on JJ stents placed in domesticated cats appears to be decreased as compared to humans. Our study tests the hypothesis that this may be due to specific differences in the chemical composition of human and feline urine. Artificial human and feline urine solutions were used in an in vitro encrustation model where an 80 % stent encrustation could be expected after 7 weeks of incubation. Scanning electron microscopy (SEM) was used to analyse crystal morphology. Energy dispersive X-ray spectrometry (EDS) was used to assess composition weight. The percentage of surface coverage of encrustation on the respective stents was quantified using image J Java plug-in software. No significant difference was observed between both solutions with regard to quality and quantity of stent encrustation. Crystals were formed in both solutions as a mixture of Ca-dihydrate and Ca-monohydrate. The study shows that there is no significant difference in the rate of encrustations on JJ stents incubated in artificial feline or human urine. This suggests that a possible difference in stent encrustation between cats and humans is due to factors other than the inorganic biochemical composition of the urines alone. Keeping in mind a true species difference, analysis of urinary macromolecules and proteins will be the logical next step.


Stent Encrustation Artificial urine Feline urine Human urine Calcium Oxalate Crystallization 


Conflict of interest

The authors declare no conflict of interest.


  1. 1.
    Syme H (2012) Royal Veterinary College. Hatfield, UK (personal communication)Google Scholar
  2. 2.
    Doremus RH, Teich S, Silvis P (1978) Crystallization of calcium oxalate from synthetic urine. Invest Urol 15:469–472PubMedGoogle Scholar
  3. 3.
    Kavanagh JP (2006) In vitro calcium oxalate crystallisation methods. Urol Res 34:139–145PubMedCrossRefGoogle Scholar
  4. 4.
    Kavanagh JP, Jones L, Rao PN (1999) Calcium oxalate crystallization kinetics at different concentrations of human and artificial urine, with a constant calcium to oxalate ratio. Urol Res 27:231–237PubMedCrossRefGoogle Scholar
  5. 5.
    Laaksovitra S, Valimaa T, Isotalo T, Tormala P, Talja M, Tammela TJ (2003) Encrustation and strength retention properties of the self-expandable biodegradable, self-reinforced l-lactide-glycolic acid co-polymer 80:20 spiral urethral stent in vitro. J Urol 170:468–471CrossRefGoogle Scholar
  6. 6.
    Malpass CA, Millsap KW, Sidhu H, Gower LB (2002) Immobilization of an oxalate-degrading enzyme on silicone elastomer. J Biomed Mater Res 63(6):822–829PubMedCrossRefGoogle Scholar
  7. 7.
    Bartges J, (2011) University of Tennessee, USA (personal communication)Google Scholar
  8. 8.
    Bartges JW, Kirk C, Lane IF (2004) Update: management of calcium oxalate uroliths in dogs and cats. Vet Clin North Am Small Anim Pract 34(4):969–987PubMedCrossRefGoogle Scholar
  9. 9.
    Hesse A, Orzekowsky H, Frenk M, Neiger R (2012) Epidemiological data of urinary stones in cats between 1981 and 2008. Tierarztl Prax Ausg K Kleintiere Heimtiere 40(2):95–101PubMedGoogle Scholar
  10. 10.
    Holmgren K (1986) Urinary calculi and urinary tract infection. A clinical and microbiological study. Scand J Urol Nephrol Suppl 98:1–71PubMedGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • M. Shafat
    • 1
  • K. Rajakumar
    • 2
  • H. Syme
    • 3
  • N. Buchholz
    • 4
    Email author
  • M. M. Knight
    • 1
  1. 1.Institute of Bioengineering, School of Engineering and Materials ScienceQueen Mary University of LondonLondonUK
  2. 2.Barts and The London Medical SchoolLondonUK
  3. 3.Royal College of Veterinary MedicineHertfordshireUK
  4. 4.Department of UrologyBarts Health NHS TrustLondonUK

Personalised recommendations