Immediate management

1. Resuscitate and treat sepsis
   • Admit to a monitored setting, often ICU if shock, organ dysfunction, altered mentation, or severe metabolic disturbance.
   • Obtain blood cultures and urine culture before antibiotics if this does not delay treatment.
   • IV fluids, vasopressors for persistent hypotension, oxygen/ventilatory support as needed.
   • Correct hyperglycemia, diabetic ketoacidosis, electrolyte disturbances, and acute kidney injury. Start renal replacement therapy if indicated.
2. Urgent CT abdomen/pelvis
   • CT is the preferred investigation because it confirms intrarenal/perinephric gas, defines the extent of disease, finds obstruction or stones, and guides drainage.
   • Distinguish EPN from emphysematous pyelitis, where gas is limited to the collecting system and is usually less severe.
     Campbell-Walsh-Wein Urology, p. 1509.
3. Start empiric IV broad-spectrum antibiotics immediately Cover common Gram-negative uropathogens, especially E. coli and Klebsiella, while considering local resistance and prior cultures.
   • Typical empiric options include an antipseudomonal beta-lactam or a carbapenem in patients with severe illness, previous resistant organisms, or high local ESBL prevalence.
   • Add MRSA or antifungal coverage only when there is a specific risk factor or culture evidence.
   • Modify treatment according to blood, urine, and drainage-fluid culture susceptibility results. Adjust doses for renal function.
   • The course is individualized, often about 2 weeks or longer if there is persistent infection, abscess, or slow clinical response.

Source control: drainage and relief of obstruction

1. Drain the infected system or collection
   • For most true EPN cases, antibiotics alone are not enough. Use percutaneous catheter drainage of renal/perinephric collections where feasible.
   • If there is ureteric obstruction from a stone, stricture, sloughed papilla, etc., perform urgent decompression with either a percutaneous nephrostomy or a ureteric stent, depending on anatomy and clinical stability.
   • Send drainage fluid for culture because it can differ from the urine culture.
   • Repeat imaging is needed if the patient does not improve or to assess resolution and drain position.

When nephrectomy is indicated

1. Urgent or delayed nephrectomy Consider nephrectomy when there is:
   • Persistent septic shock or clinical deterioration despite antibiotics, resuscitation, and adequate drainage
   • Extensive renal destruction or a nonviable kidney
   • Failure of percutaneous drainage/source control
   • Persistent or recurrent infection in a poorly functioning unilateral kidney
   • Anatomic disease not amenable to drainage

CT-based severity and risk stratification

• Class 1: Gas in collecting system only
• Class 2: Gas in renal parenchyma only
• Class 3A: Extension into perinephric space
• Class 3B: Extension into pararenal space
• Class 4: Bilateral EPN or EPN in a solitary kidney

Practical treatment algorithm

• Suspected EPN -> sepsis bundle, cultures, immediate IV antibiotics, urgent CT, early urology/IR consultation.
• Obstruction or drainable collection -> urgent nephrostomy/stent and percutaneous drainage.
• Improving clinically -> continue culture-directed therapy, manage diabetes/obstruction, repeat imaging as appropriate.
• No improvement within roughly 48-72 hours, worsening shock, or uncontrolled source -> reassess drain adequacy and consider nephrectomy.