Clinical Pearls & Morning Reports
Among young healthy women, specific virulent clones of Escherichia coli account for more than 90% of pyelonephritis cases. In contrast, among men, elderly women, and urologically compromised or institutionalized patients, less virulent E. coli strains, non–E. coli gram-negative bacilli, gram-positive organisms, and candida are more prevalent, although infections with E. coli still predominate. Antimicrobial resistance is a growing problem; the prevalence of resistance to trimethoprim– sulfamethoxazole and fluoroquinolones among E. coli isolates exceeds 10% in most surveys. Read the Clinical Practice Article here.
Q: What are the typical manifestations of acute pyelonephritis?
A: Pyelonephritis typically manifests suddenly with signs and symptoms of both systemic inflammation (e.g., fever, chills, and malaise) and bladder inflammation (e.g., urinary frequency, urgency, and dysuria). However, consensus is lacking regarding diagnostic criteria. Up to 20% of patients do not have bladder symptoms, and some patients do not have fever. Clinical presentations and disease severity vary widely, from mild flank pain with low-grade or no fever to septic shock. Rates of bacteremia vary widely across studies (ranging from <10 to >50%); rates depend on host factors and are higher among patients who are severely ill, those who are immunocompromised, those who have urinary tract obstruction, and those who are 65 years of age or older.
Q: What is the expected clinical course when pyelonephritis is appropriately treated?
A: With appropriate care, clinical manifestations usually decrease progressively, as shown by a reduction in symptoms and downward trends in the fever curve and white-cell count; however, resolution may require up to 5 days. Mild acute kidney injury from inflammation-related hemodynamic shifts is common and resolves quickly with treatment. Advanced renal failure is rare in the absence of coexisting urinary tract obstruction. Recurrent pyelonephritis is relatively uncommon (recurrence rate of <10%) and suggests a possible predisposing condition.
A: In a patient with flank pain or tenderness (with or without fever) plus a urinalysis showing pyuria, bacteriuria, or both (with or without voiding symptoms), pyelonephritis is an appropriate presumptive diagnosis. The cardinal confirmatory test is the urine culture, which typically yields 10,000 or more colony-forming units of a uropathogen per milliliter of urine. Lower counts may be present if the patient had received previous antimicrobial therapy, has extreme urine acidification, or has urinary tract obstruction. Positive blood cultures may assist in establishing a diagnosis in ambiguous cases (e.g., in populations with a high prevalence of asymptomatic bacteriuria or in patients who have received previous antimicrobial therapy), but the presence of bacteremia rarely alters management. Initial imaging to identify obstruction, abscess, or necrotizing infection is reserved for patients with sepsis or septic shock, known or suspected urolithiasis, a urine pH of 7.0 or higher, or a new decrease in the glomerular filtration rate to 40 ml per minute or lower (which is suggestive of obstruction). Effective antimicrobial therapy should be initiated promptly.
A: Practice guidelines from the IDSA and the European Society for Microbiology and Infectious Diseases address only uncomplicated pyelonephritis in women. Candidates for oral treatment are recommended to receive an initial supplemental dose of an aminoglycoside or ceftriaxone if, among local uropathogens, resistance to the selected oral agent (with a fluoroquinolone being the favored agent) exceeds a prevalence of 10%. On the basis of available clinical trial data, recommended treatment durations are 5 days (levofloxacin, 750 mg daily), 7 days (standard or high-dose extended-release ciprofloxacin), 14 days (trimethoprim–sulfamethoxazole), and 10 to 14 days (oral beta-lactams).