Depending on the severity of the clinical syndrome, acute pyelonephritis may require more extensive imaging diagnostics. In the uncomplicated form of the disease, ultrasonography does not appear to be absolutely necessary. In clinically severe cases, however, which fail to respond to antibiotic therapy, ultrasound is the optimal procedure for ruling out urinary tract obstruction. Where there is clinical suspicion of complications proven risk factors, persistent fever and/or continuing pathological inflammation parameters (elevated C-reactive protein levels in serum)-ultrasonography is the primary imaging technique for the exclusion of pyonephrosis, as well as for other complicating factors such as calculi, etc. In cases of insufficient response to antibiotic therapy, we recommend performing a renal computed tomography scan with contrast medium, in order to rule out hypoenhancing zones as hints for severe tissue alterations. This procedure is in accordance with the suggestions of the Society for Uroradiology. In the future, DMSA scintigraphy might constitute an equivalent diagnostic method for the exclusion of these focal inflammatory changes. Above all, DMSA scintigraphy makes it possible to anticipate the development of scars following acute pyelonephritis.