6340 TUBULOINTERSTITIAL NEPHRITIS: DIFFERENT SIDES OF THE SAME COIN

Abstract Background and Aims Tubulointerstitial nephritis (TIN) in pediatrics represents 7% of the causes of acute kidney injury (AKI) and a syndrome with a variety of manifestations, even with oligosymptomatic pictures, with the classic triad (fever, eosinophilia and exanthema) being observed in only 10%.the causes are multiple (pharmacological 70%) and can be associated with clinical syndromes. The diagnosis is defined by histology, but renal biopsy is not always performed due to the rapid and good evolution of some patients. The pathogenic mechanism is immune-mediated, self- limited, reversible and acute, and can evolve to tubulointerstitial fibrosis and CKD. the aim of our study is to describe the clinical characteristics of patients with TIN. Method Retrospective descriptive study conducted during 9 years (2013-2022) of a series of cases with a diagnosis of TIN (with/without biopsy), evaluating demographic, etiological, clinical-analytical, evolution and treatment parameters. Patients with previous renal disease or renal transplantation were excluded. KDIGO 2012 criteria were used to evaluate ARD, glomerular filtration rate was estimated using the Schwartz 2009 equation (0.413) in >1 year, and by CKD-EPI in >12 years. Regarding Cystatin C, the estimation was performed by the Filler formula. Proteinuria was expressed as IPr/Cr (mg/mg) and Alb/Cr (mg/mmol).Fractional excretion of solutes was analyzed, using urinary Beta-2-microglobulin (ug/ml) as a marker of tubular injury. Results Eighteen cases were identified, with a median age of 14 years (2-7 years). 11 renal biopsies were performed (61.1%), with the reason for indication generally being persistent ARD of non-filial etiology despite supportive treatment.11 pharmacological cases were identified (61.1%),3 infectious (bacterial,2 by Mycoplasma Pneumoniae),2 TINU and 2 idiopathic. The most common symptom was abdominal pain (94%) and the most frequent sign was fever (94%), with prolonged febrile syndrome in 4 children. The most common symptom was abdominal pain (94%) and the most frequent sign was fever (44.4%), with prolonged febrile syndrome in 4 children. The classic triad was detected in two cases (11.1%).On admission, all patients had normal BP, with only one patient oliguric on debut. The delay from clinical onset to diagnosis was a median of 8.5 days (IQR 20.5). Renal ultrasound showed renal hyperechogenicity (25%) and associated nephromegaly (12.5 %).median eGFR at one month was 79.72 mL/min/1.7