Over one third of women in England report having had a urinary tract infection (UTI) in their lifetime. In Scotland, UTIs are the most prevalent healthcare-associated infection within inpatient adult care.[3]

Acute uncomplicated pyelonephritis occurs primarily in younger women.[4] Complicated acute pyelonephritis tends to occur in men, older people, pregnant women, and those with underlying anatomical or physiological abnormalities, immunosuppression, an obstruction, catheterisation, incorrect antibiotic selection and usage, and resistant organisms.[5] Contemporary observation indicates that slightly more than 20% of renal transplant patients suffer from acute pyelonephritis.[6] About 30% to 50% of renal transplant patients suffer from acute pyelonephritis within 2 months after surgery in older accounts.[2] The incidence of acute pyelonephritis in pregnant women is between 0.5% and 2%.[7]

Risk factors

Risk factor for acute uncomplicated case.

If female and occurs in the previous 12 months, an increased risk of developing symptoms (odds ratio of 4.4).[8]

Previous urinary tract infection may predispose to a subsequent urinary tract infection through behavioural, microbiological, or genetic factors.[8]

If occurs in the previous 30 days, associated with an increased disease risk (odds ratio of 12.5).[8]

Medication-treated diabetes is reported as a risk factor for urinary tract infection in post-menopausal women.[18][19]

Increased prevalence of asymptomatic vaginal Escherichia coli colonisation among post-menopausal women with diabetes who are receiving insulin treatment.[20]

Greater adherence of uropathogenic E coli to uroepithelial cells may be related to impaired cytokine secretion and reduced polymorphonuclear inflammatory response.[21]

Risk factor for uncomplicated disease, associated with an odds ratio of 3.9.[8]

Risk factor for complicated cases.

Renal stones allow bacteria to remain hidden in the interior of the stone, whereas indwelling catheters may allow bacteria to form a biofilm, which helps resist antibiotic treatment.

Risk factor for complicated disease.

Such abnormalities include polycystic kidney disease, enlarged prostate, vesicoureteric reflux, ureteroceles, and neurogenic bladder.

Anatomical problems such as renal cysts and ureteroceles allow bacteria to remain in hard-to-access locations in the body (e.g., inside cysts).

Functional abnormalities such as neurogenic bladder and reflux increase likelihood that the kidneys will be exposed to bacteria.

Risk factor for complicated cases.

Immunosuppression can occur to varying degrees, which will determine the kinds of infections that are more likely and the degree of risk associated with these infections.

Corticosteroids suppress the entire cytokine and inflammatory cascade, making infections with all agents more likely, whereas only a slight decrease in CD4 count with HIV may not increase infection risk.

Risk factor for complicated disease.

The enlarging uterus compressing the ureters and the increasing laxity of the pelvic support system with the hormonal changes promote the likelihood of obstructive uropathy.

Risk factor for uncomplicated disease.

Women reporting a frequency of sexual intercourse ≥3 times per week in the previous 30 days were more likely to develop disease (odds ratio of 5.6).[8] An odds ratio of 1 implies that the event is equally likely in both groups. An odds ratio >1 implies that the event is more likely in the first group. An odds ratio <1 implies that the event is less likely in the first group. The mechanical action of sexual intercourse may facilitate entry of Escherichia coli strains into the bladder. [22]

Risk factor for uncomplicated disease (odds ratio 1.6).[8]

Suggests a role for genetic or long-term environmental exposures.[23]

Risk factor for uncomplicated disease, associated with an odds ratio of 2.2.[8]

Associated with an odds ratio of 1.7.[8]

May alter the normal lactobacillus-dominant vaginal flora and facilitate Escherichia coli colonisation of the vagina.[24]

Uncomplicated disease is diagnosed most often in adult women between these ages.[25]

Risk factor for complicated disease.

The risk of other medical problems, such as diabetes and enlarged prostate, increases with age.

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