You are at risk of developing pyelonephritis if you have abnormalities in the urinary tract causing disturbances in the flow of urine. The abnormalities can be vesicoureteral reflux(VUR) esp in little children(urine flows back from the bladder into the ureters), calculi(kidney stones), urinary tract catheterisation, urinary tract stents or drainage procedures, pregnancy, neurogenic bladder(eg due to spinal cord damage, spina bifida or multiple sclerosis) and prostate disease(eg benign prostatic hyperplasia) in men.
Attribution: Avallain