['To evaluate the effect of preoperative antimicrobial administration on culture results in dogs undergoing cystotomy as a treatment for urolithiasis.', 'Prospective controlled study. Animals-41 dogs undergoing cystotomy for cystic calculi removal.', 'Urine samples were collected at time of anesthetic induction and during surgery prior to cystotomy, and a mucosal biopsy and culturette swab was collected during surgery from a control group, which received antimicrobials only after surgical culture sample collection, and from an experimental group, which received antimicrobials at the time of anesthetic induction.', '17 of 41 patients had positive culture results at anesthetic induction. Twenty of 41 patients had positive results of cultures for the surgical sample. No dogs that had positive results before antimicrobial administration had negative results after antimicrobial administration. There were no significant changes to urinalysis results regardless of group. Calcium monohydrate uroliths were the most common stone removed (24/41), followed by magnesium ammonium phosphate uroliths (11/41).'] Does the effect of preoperative antimicrobial administration on culture result in dogs undergoing cystotomy?