A urinary tract infection (UTI) affects the urinary system, including the bladder, urethra, ureters, and kidneys. UTIs are common outpatient infections, causing millions of office visits annually. The vast majority occur in women; estimates suggest 50% to 60% of adult women will experience at least one UTI. This high prevalence often leads to questions about the risk of passing the infection to a male partner.
Understanding What Causes a UTI
The overwhelming cause of a UTI is the presence of bacteria, specifically Escherichia coli (E. coli), which is responsible for up to 90% of cases. This bacterium naturally resides in the gastrointestinal tract and can enter the urinary tract through the urethra. The urinary tract is normally a sterile environment, but once bacteria ascend the urethra and begin to multiply in the bladder, an infection can take hold.
A UTI is generally classified as either uncomplicated or complicated. Uncomplicated UTIs are common bladder infections that occur in otherwise healthy, non-pregnant women. A complicated UTI involves factors that make the infection harder to treat, such as structural abnormalities or an infection that has reached the kidneys. In men, any UTI is categorized as complicated due to the lower incidence and the likelihood of an underlying cause.
The Risk of Sexual Transmission to Men
A woman cannot directly transmit a UTI to a male partner in the same way a virus or true sexually transmitted infection (STI) is passed. UTIs are not classified as STIs because the bacteria typically originate from the woman’s own digestive tract. However, sexual activity can play a role by physically introducing bacteria into the man’s urethra, potentially leading to an infection.
The male anatomy offers a natural defense against ascending bacteria. The male urethra is longer than the female urethra, which creates a greater distance for bacteria to travel to reach the bladder. This length makes bacterial colonization and subsequent infection more difficult. Bacteria from the female genital area can still be transferred to the male’s urethral opening during intercourse.
The physical friction of sex can push bacteria into the male urethra, increasing the risk of developing urethritis or a UTI. The body’s natural defenses, including the flushing action of urination, usually clear these bacteria before a full infection develops. For this reason, the occurrence of UTIs in men is significantly lower than in women, occurring in about one in 20 men over a lifetime.
Common Causes of UTIs in Men
When a man does develop a UTI, it is most often due to a pre-existing structural or functional issue within the urinary tract rather than sexual contact. In men over 50, the most frequent cause is the noncancerous enlargement of the prostate, known as benign prostatic hyperplasia (BPH). An enlarged prostate can obstruct the flow of urine, preventing the bladder from fully emptying.
This incomplete emptying creates a pool of stagnant urine, which provides an environment for bacteria to multiply and cause an infection. Other common causes include kidney stones, which can block the urinary tract, or the use of urinary catheters. Chronic bacterial prostatitis, an infection or inflammation of the prostate gland, can also be a source of recurring UTIs because bacteria become trapped within the gland’s tissue.
Hygiene and When to Consult a Doctor
Simple hygiene practices during intimacy can help reduce the already low risk of bacterial introduction. Urinating immediately after sexual activity is an effective action for both partners, as it helps flush out any bacteria that may have entered the urethra. Maintaining cleanliness of the genital area before and after sex is also a sensible precaution to minimize the presence of bacteria near the urethral opening.
Recognizing the symptoms is important for timely treatment and preventing the infection from spreading to the kidneys. Signs of a lower UTI include a persistent, strong urge to urinate, a burning sensation during urination, and passing frequent, small amounts of urine. If these symptoms appear, or if a fever, flank pain, or blood in the urine occurs, a medical professional should be consulted promptly. A doctor can diagnose the infection with a urine test and prescribe antibiotics to resolve the infection.