Obstructive Pyelonephritis
When a kidney stone causes infection and fever, this condition is called obstructive pyelonephritis, and it represents a urologic emergency that can rapidly progress to sepsis and death 1.
Clinical Terminology and Context
The term "obstructive pyelonephritis" specifically describes the scenario where a kidney stone blocks urinary flow and causes acute infection of the kidney and renal pelvis. This is distinct from:
- Infection stones (struvite stones) - stones that form because of urease-producing bacterial infections
- Secondarily infected stones - metabolic stones that passively trap bacteria from coexisting UTIs 1, 2
Why This Is an Emergency
Obstructive pyelonephritis is fundamentally different from uncomplicated acute pyelonephritis because the obstruction prevents adequate drainage and antibiotic penetration. This creates a closed-space infection under pressure that can lead to:
- Rapid progression to sepsis
- Systemic inflammatory response syndrome (SIRS) 3
- Acute kidney injury 3
- Death if not promptly treated 1, 4
The mortality rate is approximately 3% even with modern treatment, with half of deaths occurring from acute septic complications 4.
Epidemiology
Population-based data from Sweden shows an incidence of 11.8 cases per 100,000 inhabitants annually, predominantly affecting elderly patients (median age 68 years) with a slight female predominance (56%). Notably, 16% of patients require ICU admission 4.
Critical Management Principle
The mainstay of emergency treatment is prompt drainage of the obstructed collecting system - antibiotics alone are insufficient when obstruction is present 5, 6. Definitive stone treatment is delayed until the acute infection has cleared 6.