Best Practices & Benign Disease
Introduction & Objective : Current guidelines recommend treatment of positive preoperative cultures for percutaneous nephrolithotomy (PCNL) without a consensus on the duration of treatment. Furthermore, recent literature states that positive intraoperative stone cultures are associated with a higher rate of sepsis, again without clear guidance on directing therapy. We hypothesized that there is a minimum number of days needed to properly treat a documented UTI and that untreated stone cultures are associated with post-PCNL sepsis.
Methods : The records of 147 consecutive PCNL procedures for nephrolithiasis between January and August 2015 were reviewed. Pretreatment with oral or intravenous antibiotics is based on culture sensitivities. Most are discharged with three to five days of cephalexin or amoxicillin/clavulanate depending on surgeon preference. We stratified patients who developed sepsis from those who did not and then noted patients with positive pre-op or intra-op cultures. We summarized the organisms, antibiotic given, and duration.
One hundred forty operations met the inclusion criteria. Thirteen patients (9.3%) met sepsis criteria. Of those, 9 (69%) had a positive pre-op urine culture. In comparison, 46 of 127 (36%) patients who did not have post-PCNL sepsis also had positive bladder urine cultures (p=0.02). The duration of antibiotic therapy differed: 2 days (σ 1.4) versus 4.5 days (σ 2.5) in the sepsis versus no sepsis groups respectively (p=0.02).
Thirty-four patients had a positive intra-op stone or kidney urine cultures, 5 (38.5%) in the sepsis group and 29 (22.8%) in the no sepsis group (p=0.21). Eleven of 35 (31.4%) intra-op cultures were concordant with the preoperative culture. Only two cultures showing candida were explicitly treated, and the rest had no impact on the clinical course. In four cases, preoperative cultures resulted as gram positive organisms or contaminated were associated with staphylococcus or streptococcus in the stone cultures.
Conclusions : A longer preoperative antibiotic duration decreases the risk of post-PCNL sepsis in patients with positive preoperative cultures. Intra-op stone and urine cultures may have less role in guiding therapy than previously though. One theory is that PCNL creates a low-pressure system minimizing pyelo-venous backflow. Furthermore, many of the organisms cultured may already be covered with routine post-op antibiotics. We also found that cultures showing gram positive organisms or contaminated may be associated with colonized stones and ought to be adequately pre-treated.