Several mechanisms prevent the ascent of uropathogenic bacteria from the bladder to the kidney, which can lead to pyelonephritis. A new study by Menna Clatworthy and colleagues clarifies the role of neutrophil extracellular traps (NETs) in this protection.

Noting the presence of neutrophils in urine from individuals with a negative leukocyte esterase urine dipstick test (which is typically thought to detect neutrophils in urine as a UTI marker), the researchers also demonstrated that the test was positive only in the presence of NETosing, and not intact, neutrophils.