Determination of the cause of selected canine urolith formation by advanced analytical methods.

OBJECTIVE The goal of this study was to determine the cause of selected canine urolith formation using less conventional but more advanced analytical methods. METHODS A routine laboratory specialising in urinary calculi analysis noticed a special type of core zone in some canine uroliths, which was typically made up of cylindrical holes. Of 4028 canine samples analysed, non-absorbable suture material was detected in 9 (0·22%) cases. A hollow cylindrical central area was found in a further 13 (0·32%) samples. X-ray microtomography (μCT) was utilised in order to reveal the channel structure inside this urolith sample. Matrix-assisted laser desorption-ionisation - time of flight mass spectrometry was used in order to assess the cause of this urinary stone formation. RESULTS The diameter of the channel structure corresponded with the diameter of the previously utilised suture material and indicated that this urolith was formed around residual suture material. Further confirmation was provided by the comparative matrix-assisted laser desorption-ionisation - time of flight mass spectrometry chemical analysis. This channel structure is formed by a surgical thread that serves as a base for the urolith growth. CLINICAL SIGNIFICANCE Results of this study confirm the causative role of absorbable suture material in the pathogenesis of hollow channel structures in some canine compound uroliths.