Acute pyelonephritis (APN) corresponds to infections of the renal parenchyma. The annual incidence of these infections is estimated at 4-6 million cases in France, with 60 to 90% of patients managed in general city medicine. The ceftriaxone, parenteral third-generation cephalosporin (C3G), occupies an important place in the antibiotic treatment of these infections: this is the recommended probabilistic treatment, and in some situations the treatment can be continued in its entirety via a Ceftriaxone monotherapy.