Hyponatremia and other potential markers of ultrasound abnormalities after a first febrile urinary tract infection in children.

"Declarations Ethics approvalAll procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. This study protocol was reviewed and approved by Hospital Universitario La Paz Ethics Committee, approval number HULP: PI-4495. The study has been granted an exemption from requiring written informed consent by Hospital Universitario La Paz Ethics Committee. Competing interestThe authors have no relevant financial or non-financial interest to disclose. Competing interest The authors have no relevant financial or non-financial interest to disclose."

"Funding Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This work has been financed with the Research grant 2021 of the Spanish Society of Pediatric Emergencies (SEUP)."