What Causes a UTI?

What Is a Urinary Tract Infection?

A urinary tract infection (UTI) occurs when bacteria enter the urinary system - which includes the kidneys, ureters, bladder, and urethra. The vast majority of UTIs affect the lower urinary tract: the bladder (cystitis) and the urethra (urethritis).

The Main Culprit: E. coli

Approximately 80-90% of UTIs are caused by Escherichia coli (E. coli), a type of bacteria normally found in the digestive tract. When these bacteria migrate from the anal area to the urethra, they can travel up into the bladder and multiply, causing infection.

Other bacteria that can cause UTIs include:

• Staphylococcus saprophyticus (common in young women)
• Klebsiella pneumoniae
• Proteus mirabilis

Why Are Women More Susceptible?

Women get UTIs up to 30 times more often than men. This is primarily due to anatomy:

• Shorter urethra: Women have a urethra that's about 1.5 inches long (vs. ~8 inches in men), giving bacteria a shorter path to the bladder
• Proximity: The female urethra is close to both the vagina and the anus, increasing exposure to bacteria
• Hormonal changes: Menopause reduces estrogen, which normally helps maintain protective vaginal bacteria

Common Risk Factors

• Sexual activity: Intercourse can push bacteria toward the urethra ("honeymoon cystitis")
• Certain birth control: Diaphragms and spermicides can promote bacterial growth
• Pregnancy: Hormonal changes and pressure on the bladder increase risk
• Menopause: Reduced estrogen changes the vaginal microbiome
• Urinary retention: Not fully emptying the bladder allows bacteria to grow
• Diabetes: Higher sugar in urine can promote bacterial growth
• Catheter use: Direct route for bacteria into the bladder

When to Seek Care

Most uncomplicated UTIs are easily treatable with a short course of antibiotics. If you're experiencing burning urination, urgency, or frequency - these are classic signs. However, if you develop fever, back pain, or nausea, seek immediate in-person care as these may indicate a kidney infection.