If you have a patient with a staghorn stone and the preoperative urine culture is sterile, does that mean that the stone is likewise sterile? The answer is No. If the preoperative urine culture is positive, is this always the same bacteria that is also harbored within the stone? The answer is again No.
In this study, among 75 consecutive patients having both urine and stone cultures, half (51%) had either a positive urine culture and/or stone culture. Of note, 25% of the patients with a sterile urine culture had a positive stone culture; while only 3% of patients with a positive urine culture had a negative stone culture.
In only 15% of cases was the same pathogen cultured from stone and urine; while in 8% a different pathogen was cultured from stone and urine. Bottom line is, definitely try to sterilize the urine prior to a percutaenous procedure, treat any positive urine culture prior to the procedure, but also obtain a stone culture as this may guide further antibiotic therapy should the patient need a second look procedure or should the patient develop urosepsis postoperatively that does not respond to the initial round of antibiotics. Indeed, the chance of a systemic inflammatory response syndrome increases nearly 4 fold when the stone culture is positive.
By Ralph V. Clayman, MD
Reference:
Urology 67: 26-29, January 2006
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16413326&query_hl=1&itool=pubmed_docsum