Acute pyelonephritis is an infection of the renal pelvis and kidney that usually results from ascent of a bacterial pathogen up the ureters from the bladder to the kidneys.Watch this video to learn more about this disease. 0:25 Overview 0:50 Tubulointerstitial nephritis 3:15 Pyelonephritis 4:00 Pathogenesis 10:40 Acute pyelonephritis 11:20 Morphology 12:06 Complications 12:55 Clinical features 13:40 Prognosis