What causes a urinary tract infection in men?

Howard E. Lewine, MD
It depends upon which part of the urinary tract has become infected.

Urinary tract infections in men include those that involve the:
  • Urethra, causing urethritis (The urethra runs from the opening at the tip of the penis to the bladder.)
  • Bladder, causing cystitis
  • Prostate, causing prostatitis
  • Kidney, causing pyelonephritis
Urethritis in men is most often caused by a sexually transmitted infection, such as gonorrhea or chlamydia. However, on rare occasions, bacteria can enter the tip of the penis. Usually urine will wash bacteria away before they can infect the lining of the urethra. But on rare occasion, it can cause an infection.

Bladder infections in men occur much less frequently than they do in women. A man has a longer urethra. This makes it harder for bacteria to get into the bladder. Because bladder infections in men are uncommon, men who have more than one bladder infection should be evaluated for a possible underlying cause. They could have a variation in the normal tract that makes it easier for bacteria to get into the bladder.

Prostatitis can occur from bacteria that make their way from the bladder to the prostate gland. Prostatitis is rarely related to a sexually transmitted infection.

A few bacteria can make it from the urethra all the way to the kidneys. They then can multiply and cause an infection. A kidney can also become infected if there are bacteria in the blood that then get into the kidney.

Men who engage in anal sex have a higher risk of all the above types of urinary tract infection.