Defined as the presence of 6-10 or more neutrophils per high power field of unspun, voided mid-stream urine, it can be a sign of a bacterial urinary tract infection.

Others additionally require discoloration, clouding or change in the smell of urine for a pyuria to be present.

It is often caused by sexually transmitted infections, such as gonorrhea, or viruses which will not grow in bacterial cultures.

[2] However, there are many known causes, including systemic or infectious disease, structural and physiological reasons, intrinsic kidney pathology, or drugs.

[6] Leukocyturia is mostly a sign of urinary tract infection, especially if significant bacteriuria is found (for most people, the number of bacteria in a culture is > 10^5) and other symptoms associated with passing urine.