CATALIN PRICOP, ILEANA ADELA VACAROIU, DANIELA RADULESCU, DANIEL ANDONE, DRAGOS PUIA RENAL IMPAIRMENT IN YOUNG PATIENTS WITH UNILATERAL URETERAL LITHIASIS OBSTRUCTION: WHAT FACTORS CAN BE RESPONSIBLE? In the literature, occurrence of acute kidney injury (AKI) in young patients with unilateral ureteral lithiasic obstruction and without previous renal impairment is not very often reported, and the underlined pathophysiological mechanisms are poorly known; according to some studies, it is a false kidney failure, the increase in serum creatinine being due to absorbtion of obstructed urine in the affected kidney. We have conducted a retro and prospective study in order to identify the possible risk factors that can cause renal function impairment in young patients (18-40 years) with unilateral ureteral lithiasis obstruction and a normal contralateral kidney. Results. From 402 patients included in the study, 20.64% (83 cases) presented with serum creatinine > 1.3 mg/dL. In patients with renal impairment, prevalence of male gender and history of NSAIDS use before admission were significantly higher than in non-AKI group. Serum urea/creatinine ratio, and estimated glomerular filtration rate (MDRD formula) were significantly higher, and respectively lower in AKI group. We found no significant differences between the two groups regarding age, prevalence of urinary tract infection after relief of obstruction, C-reactive protein value, and the duration of hospitalization. Conclusions. AKI in young patients with unilateral ureteral lithiasis obstruction and normal contralateral kidney is not quite a rare finding in our region. NSAIDs use can influence development of AKI, and should be used cautiously even in young patients with renal colic. In our opinion, the presence of AKI in patients with unilateral hydronephrosis demands urgent endourological intervention. Choosing conservative therapy in these patients, especially treatment with NSAIDS may aggravate the renal dysfunction.