#AUA14 - Comparative analysis of stone composition and stone culture after percutaneous nephrolithotomy - Session Highlights

ORLANDO, FL USA (UroToday.com) - Urinary sepsis following percutaneous nephrolothitomy (PCNL) is a potentially devastating complication that often occurs despite preoperative evaluation and treatment of urine cultures (UCx). The presence of infectious microorganisms harbored in urinary stones are the main cause, which is inferred from stone composition, most commonly by the presence of struvite.

Larson and colleagues performed a study to evaluate the relationship between UCx, stone culture (SCx) and stone composition to guide antibiotic therapy and reduce infectious complications.

auaThe authors retrospectively reviewed 136 consecutive PCNLprocedures performed by a single surgeon at one institution from Jan 2012 to Oct 2013. Inclusion criteria for this study comprised patients who had urine and stone cultures as well as stone analysis for mineral content.

A positive correlation between UCx and SCx occurred in 109 cases and the level of discordance was similar in both the struvite, apatite but less in the non-struvite/apatite group. A positive SCx with negative UCx occurred in 12.5% of patients overall but occurred more commonly in the struvite and apatite groups. Of patients presenting with positive UCx and SCx (n=43), 13 or 30.2% (9.6% overall) had different organisms between the UCx and SCx. UCx showed no association with stone mineral content, but SCx was more frequently positive in struvite (84.2%) and apatite (65.7%) compared to non-struvite/apatite (25.6%) stones. There was not a significant correlation between stone composition and bacterial species in either UCx or SCx; there was, however, a 100%, 73% and 33% correlation between UCx and SCx for Enterococcus, Proteus and E.Coli respectively.

In this study, almost quarter of patients had a positive stone culture after sterile urine or a different organism comparing stone-to-urine culture. When treating these infections a stone culture is essential to accurate microbial identification and antibiotic selection. Furthermore, authors concluded that that a preoperative urine culture with either Enterococcus or Proteus was highly predictive of the stone culture, allowing confidence in treating these infections based on UCx alone.

Presented by Jeffrey Larson, MD at the American Urological Association (AUA) Annual Meeting - May 16 - 21, 2014 - Orlando, Florida USA

St. Louis, MO USA

Written by Zhamshid Okhunov, MD, University of California (Irvine), and medical writer for UroToday.com