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Background: Infection is a rare complication of percutaneous renal biopsy (RB). However, the questionnaire included in the Kidney Biopsy Guidebook 2020 in Japan revealed that antibiotic prophylaxis (AP) was administered at about 60% of hospitals. The objective of this study was to evaluate whether it is possible to omit AP for RB., Methods: Patients aged ≥ 15 years were eligible. Three hundred and sixty-four patients were recruited at 6 hospitals. The patients were randomly assigned to receive either a single dose of intravenous cefazolin or no antibiotic prophylaxis. The primary outcome was the percentage of patients that exhibited positive urine cultures 3 or 4 days after the RB. The secondary outcomes were the percentage of patients who were diagnosed with pyelonephritis, puncture site infections (PSI), or an infection other than pyelonephritis or PSI within 30 days, and cefazolin-induced side effects., Results: With regard to the primary outcome, there was no statistically significant difference between the cefazolin group and the no AP group (2.9% versus 5.1%, p = 0.416). With regard to the secondary outcomes, only one patient (who belonged to no AP group) developed pyelonephritis. This patient underwent urinary catheterization. No PSI occurred. There were no significant intergroup differences in any secondary outcomes., Conclusion: This study revealed the incidence of post-percutaneous RB infections was minimal. Although the outcomes of this study did not lead to the conclusion that it is unnecessary to use AP for RB, the obtained data suggest that the effects of such AP may not be clinically significant., Competing Interests: Declarations. Conflict of interest: The authors declare the conflicts of interest. Ethical approval: All procedures performed in studies involving human participants were carried out in accordance with the ethical standards of the relevant institutional and/or national research committee (IRB approval number 1000) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed consent: The study participants provided written informed consent., (© 2024. The Author(s), under exclusive licence to Japanese Society of Nephrology.)

Background: Lipocalin 2 (LCN2 or neutrophil gelatinase-associated lipocalin) is a secretory protein discovered from neutrophils, which accumulates in the blood and urine during acute kidney injury (AKI) and in the blood by bacterial infection. Little is known about the tissue source and molecular forms of this protein under normal and pathophysiologic conditions., Methods: By sandwich ELISA, serum and urinary LCN2 levels were measured in 36 patients with hematologic malignancies who transiently became neutropenic by stem cell transplantation (SCT). To evaluate contribution of neutrophil-derived LCN2 in the physiologic blood LCN2 concentrations, we examined CCAAT/enhancer-binding protein ε (C/EBPε) knockout mice, which lack mature neutrophils., Results: In patients without AKI and bacterial infection, at 1 week after SCT, the median blood neutrophil counts became zero and serum LCN2 levels were decreased by 76 ± 6 % (p < 0.01), but urinary LCN2 levels were not altered. During neutropenic conditions, bacterial infection caused only a modest rise of serum LCN2 but AKI produced a marked rise of serum and urinary LCN2 levels. Serum LCN2 concentrations in C/EBPε knockout mice were reduced by 66 ± 11 % compared to wild-type mice (p < 0.05). Blood LCN2 existed predominantly in high molecular weight forms (>100 kDa), while urinary LCN2 was mainly in low molecular weight forms., Conclusion: Our findings suggest that neutrophils are the major source of circulating LCN2 in normal and infected conditions, whereas blood and urinary LCN2 mainly derive from the kidney during AKI, and that the molecular forms and regulation of blood and urinary LCN2 are clearly distinct.