Finding a few pus cells or white blood cells (WBCs) in urine is quite normal. But too many of them may signal a problem somewhere in your urinary tract, the commonest of which is a urinary tract infection (UTI). Your lab will usually report the result as number of cells counted per high power field of the microscope (hpf) or number of WBCs/mL of urine. Usually, 5 to 10 pus cells/hpf or 105 WBCs/mL of urine is considered normal. A high number of pus cells in urine is called pyuria. When a large number of WBCs are present in urine, they may also be detected on a urine dipstick test for leukocyte esterase.
UTIs are the commonest cause of pus cells in urine. The infection could be anywhere from the kidneys to the urethra, though bladder infection (cystitis
) is the commonest. It’s generally an uncomplicated condition that can be promptly resolved with antibiotics. People with a UTI generally also have a large number of bacteria in their urine. In some cases pus cells are found in urine but no bacteria or other infectious organism is found on urine tests. The possible causes of pus cells without bacteria in urine are:
Interstitial cystitis: Interstitial cystitis is a noninfectious condition causing inflammation of the bladder. It is much more common in women than in men. Its symptoms are similar to cystitis but no organism is found on urine culture.
: Inflammation of the prostate gland in men because of infection or other causes can cause pus cells in urine.
Kidney stones: Stones cause irritation and inflammation in the urinary tract which can lead to pus cells in urine. Kidney stones nearly always also cause the appearance of red blood cells (RBCs) in urine.
Some organisms causing infections in the urinary tract do not show up on standard urine culture for indentifying bacteria, for e.g. some sexually-transmitted agents that cause urethral infection. Your doctor may have to order special tests for detecting them. Depending on your medical history and symptoms, some organisms that your doctor may want to test for are N. Gonorrhea
, Ureaplasma and Trichomonas.