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Stone Culture is Associated with Urosepsis After Endourological Procedures
Jairam R. Eswara, MD, Dianne Sacco, MD.
Massachusetts General Hospital, Cambridge, MA, USA.

BACKGROUND:
Percutaneous nephrolithotomy (PCNL) and laser lithotripsy are effective means for treating kidney stones. Urosepsis is a known complication of these procedures. We calculated the rate of urosepsis in patients who underwent PCNL or laser lithotripsy related to urine and stone culture data. We also determined how accurately these cultures predicted the pathogen causing postoperative infection.
METHODS:
We identified 94 consecutive patients who underwent PCNL or laser lithotripsy over a 4 month period at our institution from 2008-2009, all of whom had a preoperative urine culture. 69 of these patients had a stone culture obtained during surgery. The procedures included ureteroscopy and laser lithotripsy (59), percutaneous nephrolithotomy (12). All patients had negative urine cultures preoperatively or, if positive, were treated with antibiotics for 1-7 days prior to surgery. Stone fragments were obtained during the procedure and sent for microbial analysis immediately. The primary endpoint was urosepsis defined as postoperative fever and positive urine culture requiring admission. The rates of urosepsis were compared using the Fisher’s exact test.
RESULTS:
Of the 94 patients, 6 were admitted for urosepsis postoperatively. All had positive stone cultures while 3 (50%) had positive urine cultures. Of the 94, 11 had positive preoperative urine cultures and 83 had negative cultures. 3/11 (27%) with a positive urine culture were admitted for urosepsis, while 3/83 (4%) with negative urine culture were admitted for urosepsis (p=0.02). Of the 69 patients who had a stone culture obtained, 18 were positive and 51 were negative. Of the 18 with positive stone culture, 6 (33%) were admitted for urosepsis while none of the 51 with negative stone cultures being admitted (p=0.0002). Only 2/18 (11%) patients with positive stone cultures grew the same pathogen as preoperative urine culture. The urine culture obtained on readmission grew the same pathogen as the stone culture in 4/6 patients (67%) compared to 1/6 preoperative urine cultures (17%) (p=0.24).
CONCLUSIONS:
As one would expect, infected stones are associated with urosepsis. Stone culture accurately predicted the pathogen causing infection while preoperative urine culture did not. In addition, a significant number of patients developed urosepsis despite preoperative antibiotics for positive urine culture, usually with a different pathogen. These results suggest that stone culture is a more effective means than urine culture for predicting and determining treatment of urosepsis in patients undergoing endourological procedures.


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