Description
Emphysematous pyelonephritis (EPN) is a critical and life-threatening necrotizing infection affecting the renal parenchyma and surrounding structures. This pathological condition is characterized by the production of gas within the renal parenchyma, renal collecting system, or the perirenal tissue. On the other hand, Emphysematous pyelitis is a less severe form, with gas formation confined only within the renal collecting system.
Pathophysiology
EPN typically occurs due to a single or mixed organism infection. The key causative organisms are:
- Escherichia coli: Predominantly present in approximately 69% of cases.
- Klebsiella pneumoniae: Identified in about 29% of cases.
Less commonly encountered organisms include:
- Proteus mirabilis
- Pseudomonas species
- Enterobacter species
- Candida species
- Fungi such as Mucormycosis
The production of gas occurs due to the fermentation of glucose in the infected tissues, a process facilitated by these microorganisms.
Epidemiology
EPN is strongly associated with:
- Uncontrolled diabetes mellitus, which is a major risk factor seen in about 95% of the patients.
- Immunocompromised states due to conditions such as renal transplantation, HIV infection, long-term steroid use, among others.
- Urinary tract obstruction such as stones, tumors, or congenital anomalies.
- The condition is more prevalent in females, probably due to higher urinary tract infection rates.
Clinical Features
Patients typically present acutely with:
- High-grade fever, chills, and flank pain which may be unilateral or bilateral.
- Metabolic disturbances such as hyperglycemia and acidosis, a common feature in diabetic patients.
- Altered mental status or confusion due to sepsis.
- Serious complications include the progression to septic shock, multiple organ dysfunction syndrome (MODS), and even death if not treated promptly.
Pathological Features
Macroscopic
- Multiple abscess formations may be seen within the renal parenchyma.
- Areas of infarction, both micro and macro, are visible due to the thrombosis of the small and large vessels supplying the kidney.
- Gas-filled cavities within the renal tissues are a pathognomonic feature.
- Surrounding the necrotic tissue, acute and chronic inflammatory cells can be found, indicating an ongoing infectious process.
Radiological Features
The recommended imaging modality is non-contrast computed tomography (CT).
Plain Radiography
- Can identify gas in renal parenchyma and/or perinephric space, though it’s less sensitive than CT.
CT
- More sensitive in demonstrating intraparenchymal, intracalyceal, and intrapelvic renal gas.
- Emphysematous pyelitis is identified when gas is found exclusively within the renal collecting system.
Differential Diagnoses
Emphysematous pyelitis should be distinguished from emphysematous pyelonephritis. Other conditions to consider include other causes of renal gas formation such as emphysematous cystitis and renal/perirenal abscess.
Management
Management involves multiple approaches, including:
- Aggressive fluid and electrolyte resuscitation to correct any derangements.
- Empirical broad-spectrum antibiotic therapy, which can be adjusted based on culture results.
- Percutaneous drainage of abscesses and gas cavities.
- In severe, unresponsive cases or in patients with a non-functioning kidney, nephrectomy might be required.
- Optimal glycemic control in diabetic patients is crucial to prevent recurrence.