Emphysematous pyelonephritis (EPN) is a severe, necrotizing infection of the renal parenchyma, produced by gas-forming Gram-negative bacilli. Even though only few cases are reported in the literature, the disease is not so rare and can become life-threatening if the diagnose is not quick and the therapeutic messures efficient. The biochemical analysis are the first line diagnostic, indicating the severity of the infection. The aim of our study was to to evaluate the importance of biochemical parameters, as first line diagnosis and also of the microbiological parameters, as etiologic diagnosis, in severe renal infections produced by gas forming bacili mainly in diabetic patients, predominantly women, with obstructive nephrolithiasis.