Do you have copies of the bloodwork results? According to the invoice, there was no special test for THC, at least not one that you got charged for. The bloodwork on the invoice would have checked her kidneys, but not her urine for a UTI. It looks like she was given fluids and a steroid injection. It’s hard to say why she is not wanting to use the leg that had the IV. Most dogs don’t have an issue with an IV catheter. As far as I can see in the picture, the area looks fine (not swollen or red)….