Pathophysiology of Pyelonephritis
Etiology and Microbiology
- Escherichia coli accounts for more than 90% of acute pyelonephritis cases in young healthy women 1, 2
- In men, elderly women, and urologically compromised patients, less-virulent E. coli strains, gram-negative bacilli, gram-positive organisms, and candida are more common 1
Pathogenesis
- This inflammatory response leads to the formation of microabscesses that may coalesce into larger abscesses 3, 1
Risk Factors
- Factors that disrupt normal urinary flow significantly increase risk of pyelonephritis, including vesicoureteral reflux, congenital urinary tract anomalies, altered bladder function, renal calculi, and mechanical obstruction 3, 1, 4
- Additional risk factors include sexual activity, new sexual partner, spermicide exposure, genetic predisposition, and diabetes mellitus 3, 1, 2
Disease Progression
- In uncomplicated cases, the infection remains limited to the renal pelvis and parenchyma 1
- When treatment is delayed or in high-risk patients, microabscesses may coalesce to form acute renal abscesses 3, 1
- Severe cases can progress to sepsis, shock, and death if untreated 3, 1
Complications
- Renal scarring occurs in approximately 15% of patients after first episode 2
- Potential complications include acute kidney injury 1
- Long-term complications from renal scarring may include hypertension and chronic renal failure 2
Clinical Manifestations
- The inflammatory process in pyelonephritis typically manifests as systemic inflammation, flank pain and tenderness, and bladder inflammation symptoms 3, 1, 2
- Up to 20% of patients may lack typical bladder symptoms, making diagnosis challenging 1, 2
- In diabetic patients, up to 50% may not exhibit typical flank tenderness 2