Pyelonephritis is a topic covered in the 5-Minute Clinical Consult.

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  • A syndrome caused by infection of the renal parenchyma and/or renal pelvis, often producing localized flank/back pain combined with systemic symptoms, such as fever, chills, and nausea; wide spectrum from mild illness to septic shock
  • Chronic pyelonephritis is the result of progressive inflammation of the renal interstitium and tubules, due to recurrent infection, vesicoureteral reflux, or both.
  • Pyelonephritis is considered uncomplicated if the infection is caused by a typical pathogen in an immunocompetent patient with normal urinary tract anatomy and renal function.
  • System(s) affected: renal; urologic
  • Synonym: acute upper urinary tract infection (UTI)
Geriatric Considerations
  • May present as altered mental status; absence of fever is common in this age group.
  • Elderly patients with diabetes and pyelonephritis are at higher risk of bacteremia, longer hospitalization, and mortality.
  • The high prevalence of asymptomatic bacteriuria in the elderly makes the use of urine dipstick less reliable for diagnosing UTI in this population (1)[A].
Pregnancy Considerations
  • Most common medical complication requiring hospitalization
  • Affects 1–2% of all pregnancies. Morbidity does not differ between trimesters.
  • Urine culture for test of cure 1 to 2 weeks after therapy
Pediatric Considerations
  • UTI is present in ~5% of patients age 2 months to 2 years with fever and no apparent source on history and physical exam.
  • Treatment (PO or IV; inpatient or outpatient) should be based on the clinical situation and patient toxicity.


Community-acquired acute pyelonephritis: 28/10,000/year

Adult cases: 250,000/year, with 200,000 hospitalizations

Etiology and Pathophysiology

  • Escherichia coli (>80%)
  • Other gram-negative pathogens: Proteus, Klebsiella, Serratia, Clostridium, Pseudomonas, and Enterobacter
  • Enterococcus
  • Staphylococcus: Staphylococcus epidermidis, Staphylococcus saprophyticus (number 2 cause in young women), and Staphylococcus aureus
  • Candida

Risk Factors

  • Underlying urinary tract abnormalities
  • Indwelling catheter/recent urinary tract instrumentation
  • Nephrolithiasis
  • Immunocompromised, including diabetes
  • Elderly, institutionalized patients (particularly women)
  • Prostatic enlargement
  • Childhood UTI
  • Acute pyelonephritis within the prior year
  • Frequent recent sexual intercourse; spermicide use; new sex partner within the prior year
  • Stress incontinence in the previous 30 days
  • Pregnancy
  • Hospital-acquired infection
  • Symptoms >7 days at time of presentation

Commonly Associated Conditions

  • Indwelling catheters
  • Renal calculi
  • Benign prostatic hyperplasia

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