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Acute pyelonephritis

Definition
Acute pyelonephritis is a disease resulting from acute infection of the renal pelvis and kidney.
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Pathophysiology
Acute pyelonephritis is caused by uropathogenic bacteria, including E. coli (80%), K. pneumoniae (6.2%), Enterococcus (5.3%), Streptococcus agalactiae (2.8%), P. mirabilis (2%), S. saprophyticus (1.4%), K. oxytoca (0.9%) and P. aeruginosa (0.8%).
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Epidemiology
In the US, the estimated incidence of acute pyelonephritis requiring hospitalization is 117 cases per 100,000 person-years among females, and 24 cases per 100,000 person-years among males.
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Disease course
In patients with acute pyelonephritis, bacterial colonization and toxin production in the renal parenchyma leads to an inflammatory response and immune cell recruitment. Host-bacteria interaction leads to local tissue alterations (coagulation, epithelial breakdown, vascular leakage, and tissue destruction). Progression of infection may be associated with renal abscess, bacteremia, septic shock, and death.
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Prognosis and risk of recurrence
In patients with associated sepsis, mortality approaches 10-20%.
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Key sources
The following summarized guidelines for the evaluation and management of acute pyelonephritis are prepared by our editorial team based on guidelines from the European Association of Urology (EAU 2023), the American College of Obstetricians and Gynecologists (ACOG 2023), the American College of Physicians (ACP 2021), the Spanish Society of Clinical Microbiology and Infectious Diseases (SEIMC 2017), the Infectious Diseases Society of America (IDSA 2016), the Infectious Diseases Society of America (IDSA/ESCMID 2011), and the American Academy of Family Physicians (AAFP 2011).
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Guidelines

1.Screening and diagnosis

Diagnostic criteria: diagnose acute pyelonephritis in women with compatible symptoms in whom urine cultures demonstrate ≥ 10⁴ CFU/mL of a pathogenic organism.
B
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2.Diagnostic investigations

Urine tests
As per EAU 2023 guidelines:
Obtain urinalysis (using the dipstick method), including assessment of WBCs, RBCs, and nitrite, for the diagnosis of acute uncomplicated pyelonephritis.
A
Obtain urine culture and antimicrobial susceptibility testing in patients with pyelonephritis.
A

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  • Blood tests

  • Urodynamic testing

  • Urinary tract imaging

3.Medical management

Setting of care: consider treating women with uncomplicated acute pyelonephritis and mild-to-moderate symptoms (fever < 39 °C, no severe flank pain, no vomiting) as outpatients.
B

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  • Route of administration

  • Empiric antibiotics (community-acquired pyelonephritis)

  • Empiric antibiotics (healthcare-associated pyelonephritis)

  • Definitive therapy

  • Duration of treatment

4.Specific circumstances

Pregnant patients, evaluation: suspect pyelonephritis in pregnant patients with fever (≥ 38.0 °C) and urine tests suggesting UTI, with additional symptoms of upper genitourinary tract infection (such as flank pain or costovertebral angle tenderness) supporting the diagnosis.
E

More topics in this section

  • Pregnant patients (setting of care)

  • Pregnant patients (antibiotic therapy)

  • Patients with urosepsis

  • Patients with complicated pyelonephritis

  • Patients with Candida pyelonephritis