Urinary Tract Infection (UTI)

Overview

A urinary tract infection (UTI) is a bacterial infection affecting any part of the urinary system, including the kidneys, ureters, bladder, and urethra. Most UTIs involve the lower urinary tract—specifically the bladder and urethra—where they cause uncomfortable but treatable symptoms. Women face significantly higher UTI risk than men, with studies indicating that 50-60% of women will experience at least one UTI during their lifetime.

UTIs develop when bacteria, most commonly Escherichia coli (E. coli) from the gastrointestinal tract, enter the urinary system through the urethra and begin multiplying in the bladder. While the urinary system has natural defences against bacterial invasion, these defences sometimes fail, allowing infection to establish.

Types of UTIs

UTIs are classified by their location within the urinary system. Cystitis, or bladder infection, represents the most common type and is often called a lower UTI. This form typically causes frequent urination, burning during urination, and lower abdominal discomfort. When caused specifically by bacteria, it is termed bacterial cystitis.

Pyelonephritis, or kidney infection, is a more serious upper UTI that occurs when bacteria ascend from the bladder to the kidneys. This type requires prompt medical treatment and may necessitate hospital admission in severe cases. Urethritis, infection of the urethra, often results from sexually transmitted bacteria and frequently occurs alongside bladder infections.

Symptoms

UTI symptoms vary depending on which part of the urinary tract is infected. Lower UTIs typically produce a persistent urge to urinate, a burning sensation during urination known as dysuria, and passing frequent small amounts of urine. Urine may appear cloudy, have a strong odour, or contain visible blood—a symptom called hematuria. Women often experience pelvic pain centred around the pubic bone.

Upper UTIs involving the kidneys produce more severe symptoms including high fever, chills, nausea, vomiting, and pain in the upper back or side. These symptoms indicate a potentially serious infection requiring immediate medical attention.

Causes

Escherichia coli bacteria cause approximately 80-90% of all UTIs. These bacteria normally inhabit the intestinal tract and can migrate to the urinary system through the urethra. Other bacterial causes include Klebsiella, Proteus, Enterococcus, and Staphylococcus saprophyticus, the latter being particularly common in sexually active young women.

Sexual intercourse increases UTI risk by potentially introducing bacteria into the urethral area. Certain contraceptive methods, particularly diaphragms and spermicidal agents, alter vaginal flora in ways that promote bacterial growth. In postmenopausal women, declining oestrogen levels cause changes to the urinary tract lining that increase infection susceptibility—a condition detailed under atrophic vaginitis.

Risk Factors

Female anatomy presents the primary risk factor for UTIs. Women have shorter urethras than men, reducing the distance bacteria must travel to reach the bladder. Sexual activity, new sexual partners, and certain contraceptives further elevate risk in women.

Urinary tract abnormalities present from birth can predispose individuals to infection. Blockages such as kidney stones or an enlarged prostate from benign prostatic hyperplasia trap urine and create conditions favourable for bacterial growth. Catheter use, whether short-term or long-term, introduces bacteria directly into the bladder and represents a significant risk factor in hospitalised patients.

Conditions that suppress immune function, including diabetes, HIV/AIDS, and immunosuppressive medications, reduce the body’s ability to fight infection. People with neurogenic bladder who cannot fully empty their bladder also face increased UTI risk due to residual urine providing a medium for bacterial multiplication.

Diagnosis

Healthcare providers diagnose UTIs through clinical evaluation and laboratory testing. Urinalysis examines a urine sample for the presence of bacteria, white blood cells, and red blood cells. A positive result indicates infection, though a urine culture provides definitive diagnosis by identifying the specific bacteria responsible and determining which antibiotics will be effective.

For patients with recurrent UTIs (three or more infections annually), additional investigations may be warranted. Imaging studies such as ultrasound or CT scan can reveal structural abnormalities. Cystoscopy, using a thin scope to visualise the bladder interior, helps identify stones, tumours, or other abnormalities that might predispose to infection.

Treatment

Antibiotics remain the primary treatment for bacterial UTIs. The specific antibiotic and treatment duration depend on the bacteria identified, infection severity, and patient factors including pregnancy status, allergies, and kidney function. Commonly prescribed antibiotics include trimethoprim-sulfamethoxazole, nitrofurantoin (Macrobid), fosfomycin (Monurol), and cephalexin. Simple lower UTIs typically resolve with three to seven days of oral antibiotics, while kidney infections may require ten to fourteen days of treatment or intravenous antibiotics.

Pain relief is an important component of UTI management. Over-the-counter medications such as paracetamol or ibuprofen reduce fever and ease discomfort. Phenazopyridine provides specific relief from urinary burning but does not treat the underlying infection and is used only as a short-term adjunct to antibiotics.

Supportive measures include increasing fluid intake to help flush bacteria from the urinary system, applying a heating pad to the abdomen to ease cramping, and avoiding irritants such as caffeine, alcohol, and spicy foods until symptoms resolve.

Prevention

Preventing UTIs involves minimising bacterial exposure to the urinary tract and supporting the body’s natural defences. Drinking adequate fluids, particularly water, promotes regular urination that flushes bacteria before infection can establish. Urinating promptly when the urge arises rather than holding urine prevents bacterial accumulation in the bladder.

Women should wipe from front to back after using the toilet to avoid transferring intestinal bacteria toward the urethra. Emptying the bladder soon after sexual intercourse helps clear any bacteria introduced during activity. Avoiding douches, powders, and other potentially irritating feminine products maintains healthy vaginal flora that resist bacterial overgrowth.

For individuals experiencing recurrent UTIs, preventive strategies may include low-dose prophylactic antibiotics, post-coital antibiotics, vaginal oestrogen therapy for postmenopausal women, or cranberry products and D-mannose supplements, though evidence for these latter options remains mixed.

When to See a Doctor

Seek medical attention if UTI symptoms persist beyond two days without improvement or worsen despite home care. Blood in the urine, fever exceeding 38°C, pain in the back or side, nausea or vomiting, and shaking chills all suggest possible kidney involvement requiring urgent evaluation.

Pregnant women should contact their healthcare provider at the first sign of UTI symptoms, as untreated infections during pregnancy carry risks for both mother and baby. Men experiencing UTI symptoms should also seek prompt evaluation, as UTIs in men often indicate underlying structural or prostatic abnormalities requiring investigation.

Anyone experiencing three or more UTIs within a year should discuss this pattern with their doctor to investigate underlying causes and develop a prevention strategy. Differentiating recurrent UTIs from interstitial cystitis—a chronic bladder condition causing similar symptoms without infection—may require specialist referral.