About 95% of urinary tract infections occur when bacteria travel up from the urethra to the bladder and, in the case of pyelonephritis, from the ureter to the kidney. The rest of urinary tract infections are hematogenous in origin. Urinary tract infections can cause systemic infections, particularly in the elderly.
Approximately 6.5% of hospital-acquired bacteraemia cases are attributable to urinary tract infections.
It is usually defined as uncomplicated urinary infection, cystitis or pyelonephritis that occurs in premenopausal adult women without any structural or functional abnormality of the urinary tract, non-pregnant and without significant comorbidities that could lead to more serious outcomes.
Furthermore, some experts believe that urinary tract infections are considered uncomplicated, even in postmenopausal women or in patients with well-controlled diabetes. In men, most UTIs occur in children or the elderly, are due to anatomical are considered complicated.
The rare urinary tract infections that occur in men between the ages of 15 and 50 occur in men who have unprotected anal intercourse or in those who do not have a circumcised penis, and are generally considered uncomplicated.
Urinary tract infections in men of this age who do not have unprotected anal intercourse or with an uncircumcised penis are very rare and, although considered uncomplicated, require evaluation to rule out urological abnormalities.
Complicated urinary tract infections can involve both sexes, at any age. It is generally considered that pyelonephritis or cystitis that does not meet the criteria should be considered uncomplicated. A urinary tract infection is considered complicated if the patient is a child, a pregnant woman, or has any of the following:
- A structural or functional abnormality of the urinary tract and an obstruction to the urinary flow
- A comorbidity that increases the risk of getting the infection or resisting treatment, such as poorly controlled diabetes, chronic kidney disease, or immunocompromised
- Recent instrumentation or surgery on the urinary tract
- Risk factors
- Risk factors for developing urinary tract infections in women are as follows:
- Sexual intercourse
- Use of diaphragm and spermicides
- Use of antibiotics
- New sexual partner in the past year
- History of urinary tract infections in 1st degree female relatives
History of recurrent urinary tract infections
- First urinary tract infection at an early age
- The risk factors for urinary tract infection in males are as follows:
- Benign prostatic hyperplasia with obstruction, common in men over the age of 50
- Any other causes of urinary tract obstruction (eg, prostate cancer, urethral stricture)
- Recent instrumental maneuvers or indwelling catheters
- Structural abnormalities, such as bladder diverticula
- Neurologic conditions that interfere with normal urination (eg, spinal cord injury)
- Cognitive impairment, faecal or urinary incontinence
The use of spermicide-coated condoms also increases the risk of urinary tract infection in women. The high risk of urinary tract infection in women using antibiotics or spermicides is likely due to changes in the vaginal flora that allow Escherichia coli to overgrow. Another risk factor in elderly women is perineum contamination linked to fecal incontinence.