Dual-Energy Computed Tomography Scan and Color Doppler Twinkling Artifact of Canine Uroliths to Determine Urolith Fragility by Laser Lithotripsy.

Abstract

Uroliths are a commonly encountered clinical problem in dogs with the majority reported in the bladder and less frequently in the urethra, kidney, and ureter. The most recent American College of Veterinary Internal Medicine (ACVIM) consensus statement on the treatment and prevention of uroliths in dogs and cats discourages cystotomy as the primary solution for uroliths and recommends that urocystoliths likely to cause urinary obstruction, recurrent infection or associated with clinical signs be removed by minimally invasive procedures. A common minimally invasive procedure is intracorporal laser using cystoscopic guidance lithotripsy. This minimally invasive procedure involves intracorporeal fragmentation of uroliths using laser energy. However, not every patient is considered for lithotripsy as there are several factors that determine whether a candidate is amenable to laser lithotripsy. The objectives of this study were to 1) Determine whether uroliths in a synthetic urine bath will have a large increase in their overall weight. 2a) Determine whether Dual energy CT measurements including dual energy number and the dual energy ratio correlates with urolith fragility by laser lithotripsy. 2b) Determine the surface roughness of these uroliths by qualitative methods to correlate this finding with urolith fragility by laser lithotripsy. 3) Determine whether the color Doppler twinkle artifact measurements both qualitatively and quantitatively determined will correlate with the urolith fragility by laser lithotripsy and will correlate with the qualitative assessment of surface roughness determined grossly and by CT evaluation. When four different types of uroliths (struvite, ammonium urate, calcium oxalate and cystine) were submerged in a synthetic urine solution over a 3-month time interval there was no significant change in weight over time. There was no single dual energy CT measurement that could be used to help predict urolith fragility on laser lithotripsy. When multiple dual energy CT measurements are included to help predict urolith fragility of laser lithotripsy, uroliths with a rougher surface fractured faster than borderline or smooth stones and uroliths without cracks fractured faster by laser lithotripsy. Twinkling artifact could not be used to help predict urolith fragility on laser lithotripsy. There was no significant association between twinkling artifact and surface roughness determined on computed tomography.