Urinary tract infection (UTI)

A urinary tract infection is an infection of any part of the urinary system — the bladder, the tube that carries urine out (urethra), or the kidneys. Most are caused by bacteria (commonly E. coli) entering from the bowel, and they are very common, especially in women because of shorter anatomy. A lower UTI (cystitis, a bladder infection) is the usual, milder form: burning or stinging on passing urine, needing to pass urine more often and more urgently, passing only small amounts, lower-tummy discomfort, and sometimes cloudy or strong-smelling urine. An upper UTI (pyelonephritis, a kidney infection) is more serious: it adds fever, chills, pain in the back or side (the loin), and feeling generally unwell, and can make people quite ill. UTIs are more concerning in men (less common, so needs assessment), pregnancy, young children, older or frail people, and anyone with kidney problems, diabetes or a catheter. They are usually diagnosed from symptoms with a urine dipstick and, when needed, a urine culture, and treated with antibiotics.

• Urine dipstick and culture — the main tests; the dipstick detects signs of infection (white cells, nitrites) and the culture identifies the bacteria and the right antibiotic.
• White cell count (WBC) and CRP — raised in a more significant infection, especially a kidney infection.
• Kidney function (creatinine, eGFR) — checked in more severe infection.
• Blood cultures — if the infection may have spread to the blood. A simple bladder infection is often diagnosed on symptoms and urine testing alone, without blood tests.

• Burning or stinging when passing urine
• Needing to pass urine more often and urgently
• Passing only small amounts of urine
• Lower-tummy discomfort or pressure
• Cloudy, strong-smelling, or bloody urine
• Kidney infection (more serious): fever, chills, pain in the back or side, nausea, feeling very unwell
• In older people, a UTI can show up as new confusion