Description

• Acute pyelonephritis is a syndrome caused by an infection of the renal parenchyma and renal pelvis, often producing localized flank/back pain combined with systemic symptoms, such as fever, chills, and nausea. It has a wide spectrum of presentation, from mild illness to septic shock.
• Chronic pyelonephritis is the result of progressive inflammation of the renal interstitium and tubules, presumed to be caused by recurrent infection, vesicoureteral reflux, or both.
• Uncomplicated vs. complicated: Presentation is considered uncomplicated if the infection is caused by a typical pathogen in an immunocompetent patient who has normal urinary tract anatomy and renal function.
• System(s) affected: Renal; Urologic
• Synonym: Acute upper urinary tract infection (UTI)

• May present only as confusion; absence of fever is common in this age group.
• Elderly patients with diabetes and pyelonephritis are at higher risk of bacteremia, long hospitalization, and mortality.

• Most common medical complication requiring hospitalization
• Affects 1–2% of all pregnancies. Morbidity does not differ between trimesters.
• Urine culture follow-up 1–2 weeks after therapy

• UTI is present in ~5% of patients age 2 months to 2 years with fever and no source evident from history and physical exam.
• Route for antibiotics and location of care should be based on the clinical situation.

Epidemiology

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

Prevalence
Adult cases: 250,000/year, with 100,000 hospitalizations

Risk Factors

• Underlying urinary tract abnormalities
• Indwelling catheter/recent urinary tract instrumentation
• Nephrolithiasis
• Immunocompromise, including diabetes
• Elderly, institutionalized women
• Prostatic enlargement
• Childhood UTI
• Acute pyelonephritis within the prior year
• Frequency of recent sexual intercourse/spermicide use
• Stress incontinence
• Pregnancy
• Hospital-acquired infection
• Symptoms >7 days at presentation

Etiology

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

Commonly Associated Conditions

• Indwelling catheters
• Renal calculi
• Benign prostatic hyperplasia