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available at http://www.ncbi.nlm.nih.gov/pubmed/30182079 Editorial Comment: Ureteroscopy for stones remains among the most commonly performed procedures by urologists today. These authors evaluated risk factors and documented pathogens that resulted in febrile urinary tract infections (UTIs) after ureteroscopy. In their study they included all patients undergoing ureteroscopy during an 18-month period. All of the patients had negative preoperative urine cultures and were given a fluoroquinolone as periprocedural antimicrobial prophylaxis. The authors found that Pseudomonas was the most common pathogen among individuals in whom postoperative UTIs developed, and the risk factor associated with febrile UTI was duration of the procedure. Further analysis of the 43 patients (14% of the entire study population) who went on to demonstrate a postoperative urinary tract infection showed that about half had bacteria that could be cultured from the blood or the urine. In these patients the most common pathogen was Pseudomonas, and 83% had pathogens that were resistant to fluoroquinolone. Thus, within this population one could extrapolate that coverage with single agent fluoroquinolone may not be the most appropriate choice. Additionally an efficient operation can reduce the risk of postoperative infection. At our institution we use double coverage with intravenous antibiotics before these procedures. This may be a reasonable consideration with close scrutiny of cost. Edward M. Schaeffer, MD, PhD Re: Renal Transplant Recipients Receiving Loop Diuretic Therapy Have Increased Urinary Tract Infection Rate and Altered Medullary Macrophage Polarization Marker Expression J. Casper, J. Schmitz, J. H. Br€ asen, A. Khalifa, B. M. W. Schmidt, G. Einecke, H. Haller and S. von Vietinghoff Department of Internal Medicine, Division of Nephrology and Hypertension, and Institute for Pathology, Hannover Medical School, Hannover, Germany Kidney Int 2018; 94: 993e1001. doi: 10.1016/j.kint.2018.06.029 Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/30274681available at http://www.ncbi.nlm.nih.gov/pubmed/30274681 Editorial Comment: This fascinating article explores possible mechanisms for development of urinary tract infections within the renal transplant population. The authors note that in a cohort of 112 adults with renal allografts use of loop diuretics in the graft population was associated with increased risk of urinary tract infections during a 5-year period after transplant. This observation was significant in univariable and multivariable regression analysis. The investigators further correlated changes in the ratios of macrophage markers and suggest that diuretic use within the transplantation population alters the corticomedullary salt gradient, and through this mechanism impacts the immune microenvironment of the kidney and potentially predisposes to urinary tract infection. I found this article to be interesting and insightful as I did not know that the corticomedullary salt gradient in the kidney modulated the adaptive and immune responses. The observations that the 12 INFECTION AND INFLAMMATION OF THE GENITOURINARY TRACT Copyright © 2019 American Urological Association Education and Research, Inc. Unauthorized reproduction of this article is prohibited.