What is xanthogranulomatous pyelonephritis in a middle‑aged to older woman with chronic urinary obstruction (e.g., staghorn calculi), recurrent urinary‑tract infections and diabetes, and how should it be managed?

Xanthogranulomatous Pyelonephritis: Definition and Management

What is Xanthogranulomatous Pyelonephritis?

Xanthogranulomatous pyelonephritis (XGP) is a rare, destructive form of chronic pyelonephritis where renal parenchyma is replaced by lipid-laden foamy macrophages (xanthoma cells), typically occurring in middle-aged women with chronic urinary obstruction from staghorn calculi, recurrent UTIs, and often diabetes. 1, 2

Key Pathophysiologic Features:

• The disease results from chronic obstructive uropathy combined with persistent infection, leading to granulomatous inflammation and complete destruction of functional renal tissue 1, 3
• Most commonly associated with staghorn calculi causing chronic ureteral obstruction 1, 4
• The affected kidney becomes enlarged, non-functioning, and filled with yellow, necrotic tissue that grossly resembles renal cell carcinoma 2, 3
• Can exhibit aggressive local tissue invasion mimicking malignancy, potentially involving adjacent organs (duodenum, pancreas, spleen) and forming fistulae (nephrobronchial, pyelocutaneous, ureterocutaneous) 3, 4, 5

Classic Clinical Profile:

• Middle-aged to older women (typically 40s-50s) 1, 2
• History of recurrent urinary tract infections 1, 4
• Presence of staghorn calculi or chronic urinary obstruction 1, 4
• Diabetes or immunocompromised state 3, 4
• May present with flank pain, fever, weight loss, or remain asymptomatic until late-stage disease 4

Diagnostic Imaging:

• CT shows the pathognomonic "bear paw sign" - dilated calyces filled with pus and debris surrounded by inflammatory tissue 1
• Often indistinguishable from renal cell carcinoma on imaging, requiring histopathologic confirmation 2, 3

Management Algorithm

Definitive Treatment: Nephrectomy

Nephrectomy is the only definitive treatment for XGP and should be performed when the diagnosis is established, as the kidney is non-functioning and serves as a persistent source of infection and morbidity. 6

Surgical Approach Selection:

Open surgical nephrectomy is preferred over laparoscopic approaches when intense perirenal inflammation from XGP is present, as it provides safer dissection planes and better control of inflammatory adhesions. 6

• Open nephrectomy is the safer approach due to the intense perirenal inflammation characteristic of XGP 6
• Laparoscopic nephrectomy may be considered in early, localized disease without extensive inflammation 6
• The combination of stones, obstruction, and recurrent infection in XGP creates a poorly functioning kidney that is a source of persistent morbidity including recurrent UTI, pyelonephritis, and sepsis 6

Pre-Nephrectomy Management:

Initial stabilization with intravenous antibiotics and percutaneous nephrostomy drainage is indicated for patients presenting with sepsis or acute infection before proceeding to definitive nephrectomy. 6, 5

• Start broad-spectrum IV antibiotics targeting common uropathogens (extended-spectrum cephalosporins or fluoroquinolones) 7
• Obtain blood and urine cultures before initiating antibiotics 7
• Place percutaneous nephrostomy for urgent drainage if patient is septic or hemodynamically unstable 6
• PCN provides both urinary decompression and bacteriological information to guide antibiotic therapy 6

Timing of Nephrectomy:

Proceed to nephrectomy after medical stabilization and resolution of acute sepsis, typically following a course of targeted antimicrobial therapy based on culture results. 5

• Delay nephrectomy until acute infection is controlled to reduce surgical morbidity 5
• In cases with fistula formation or extrarenal complications, interval nephrectomy with fistula repair is performed after prolonged medical management 5

Critical Decision Point - When Nephrectomy is Indicated:

Nephrectomy should be performed when the involved kidney has negligible function (as is typical in XGP), particularly when the contralateral kidney demonstrates normal function, to prevent further patient morbidity from recurrent infection and sepsis. 6

Common Pitfalls and Caveats

Diagnostic Pitfalls:

• Do not mistake XGP for renal cell carcinoma - both can present as enlarging renal masses with local invasion; histopathologic examination is required for definitive diagnosis 2, 3
• Do not attribute symptoms solely to nephrolithiasis or simple UTI - localized flank pain and dysuria may delay recognition of XGP until late-stage disease with complications 4
• Consider XGP in any patient with staghorn calculi and recurrent UTIs who develops a non-functioning kidney 1, 4

Management Pitfalls:

• Do not attempt nephron-sparing procedures - XGP requires complete nephrectomy as the entire kidney is typically destroyed and non-functioning 4
• Do not delay nephrectomy indefinitely - while initial medical stabilization is appropriate, definitive surgery should not be postponed excessively as this can lead to fulminant complications including fistula formation and more technically difficult surgery 4, 5
• Do not choose laparoscopic approach when intense perirenal inflammation is evident - open surgery provides safer access in this setting 6

Special Considerations:

• Screen for extrarenal complications before surgery - look for fistulae (nephrobronchial, pyelocutaneous) and adjacent organ involvement that may require additional surgical planning 3, 5
• Ensure contralateral kidney function is adequate before proceeding with nephrectomy - this is typically performed only when the opposite kidney is normal 6