UTIs are extraordinarily common but kidney infections are not—now doctors know why.

“A multidisciplinary team at Cambridge University in England solved the conundrum in an elegant series of experiments. Dr. Andrew P. Stewart and colleagues found that highly specialized biological structures called neutrophil extracellular traps—NETs—are pivotal in protecting the kidneys from infection. NETs are sticky webs of wispy strands that quite literally serve as traps. They ensnare bacteria that attempt to migrate northward to the kidneys from the lower urinary tract. NETs add to an array of antimicrobial activities mounted by the body to beat back infection.”