Epidemiology

In adults, acute pyelonephritis is estimated to account for at least 250,000 office consultations and 200,000 hospitalizations annually in the US at the estimated cost of $2.14 billion per year.[3][4][5]​​ Acute uncomplicated infections occur primarily in younger women. A 2007 population-based study reported an incidence of 12 to 13 cases per 10,000 in US women in Seattle, WA compared with 2 to 3 cases per 10,000 men in that city.[5] A 2005 study reported an incidence of 28 cases per 10,000 in US women ages 18 to 49 years.[6] Hospitalization as a result of acute pyelonephritis is 5 times more common in women than in men, with 11.7 versus 2.4 hospitalizations per 10,000 cases.[2] Women, however, show a lower mortality rate than men with 7.3 versus 16.5 deaths per 1000 cases.[2] In contrast, a South Korean database reported an incidence of 36 cases per 10,000 persons (male, 13; female, 59). Incidence varied with age, increasing dramatically in women older than age 19 years. This database also showed a seasonal variance in incidence (more common in summer).[7] Worldwide prevalence and incidence are unknown.[8]

Complicated acute pyelonephritis tends to occur in men, older people, pregnant women, and those with underlying anatomic issues (e.g., causing obstruction) or significant comorbidities (e.g., immunosuppression, diabetes). Other complicating factors include catheterization, incorrect antibiotic selection and usage, and multidrug-resistant organisms.[9][10][11]​​​​​ Contemporary observation indicates that slightly more than 20% of renal transplant patients suffer from acute pyelonephritis.[12] 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 1% and 2%.​[10][13]​​​​ ​In pregnancy, untreated pyelonephritis can lead to severe maternal and obstetric complications, including preterm labor and delivery, sepsis, septic shock, and acute respiratory distress syndrome.[10]

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