Demetrius H. Bagley, MD, FACS
Kelly A. Healy, MD
BASICS
DESCRIPTION
• Xanthogranulomatous pyelonephritis (XGP) is an uncommon chronic destructive granulomatous process of renal parenchyma in association with long-term urinary tract obstruction and infection
• Associated obstruction, stones
• Diffuse renal destruction with nonfunctioning kidney
• Local mass formation sometimes confused with malignancy
EPIDEMIOLOGY
Incidence
• Rare, occurring in 0.5–1.4% of patients with renal inflammatory disorders (1, 2)
• Female to male (3:1)
• Peak incidence in 5th–7th decade
• Reported in children as young as 6 mo
• Left = right
Prevalence
N/A
RISK FACTORS
• Diabetes
• History of stones
• History of UTIs
Genetics
N/A
PATHOPHYSIOLOGY
• Stones
• Obstruction
• Infection
• Proteus mirabilis is most common organism with Escherichia coli secondary.
ASSOCIATED CONDITIONS
• Diabetes (3)
• Renal calculi, including staghorn (35%)
• Immunosuppression
GENERAL PREVENTION
Adequate treatment and follow-up of known UTIs
DIAGNOSIS
HISTORY
• Nonspecific signs
• Fever, chills, flank pain, fatigue, anorexia
• Persistent bacteriuria even after antibiotic therapy
• ∼1/3 of XGP patients have a history of stones
• 100% found to have stones at treatment
• Diabetes common
PHYSICAL EXAM
• Fever
• Flank tenderness
• Palpable flank mass
• Rarely elevated BP
• Weight loss
• Less commonly hematuria
DIAGNOSTIC TESTS & INTERPRETATION
Lab
• Anemia 71%
• Leukocytosis 62%
• Pyuria 81%
• Urine culture: Proteus and E. coli are most common
– Mixed urine cultures occur in 10% of XGP patients
• Liver enzymes abnormal in as many as ½ of XGP patients
Imaging
• CT is the 1st-choice imaging study (4,5)
– Demonstrates stones and hydronephrosis
– Seen multiple renal calculi or staghorn calculi
– Shows enlarged kidney with mass, usually diffused
– Renal parenchyma replaced with multiple fluid-filled cavities and extension of inflammatory mass to perinephric spaces
• IV urogram shows nonvisualization in 30–80% of patients
– Stone visible in 30–80%
– Cannot distinguish renal mass from neoplasm
• Renal ultrasound demonstrates enlargement of the kidney
– Hydronephrosis
– Echogenic focus of the calculus
– Multiple anechoic areas of parenchyma
• MRI provides little additional information
• Functional renal scans can evaluate differential renal function and may confirm nonfunction of the involved kidney
ALERT
XGP may not be distinguished clinically or radiographically from renal cell carcinoma.
Diagnostic Procedures/Surgery
Diagnosis is made on the basis of clinical suspicion and radiographic imaging studies
Pathologic Findings
• Diffuse involvement of the entire kidney occurs in 80+% of cases
• Segmental involvement is much less common
• XGP commonly extends beyond the kidney and mass
– Fistulae, pyelocutaneous and ureterocutaneous have been noted
• Gross findings:
– Massively enlarged kidney
– Hydronephrosis
– Obstructing stones
– Pus-filled calyces and parenchymal abscesses
– Yellow nodules surrounding the calyces
• Microscopic findings:
– Thin cortex with extension of inflammatory response beyond kidney
– Lipid-laden macrophages (xanthoma cells) mixed with lymphocytes, plasma cells, and giant cells form sheets around the calyces and parenchymal abscesses, show grossly as yellow nodules
– Mass may resemble a renal cell carcinoma with hemorrhage, necrosis and yellow appearance in gross sectioning
– Associated rare neoplasms have been reported with XGP
DIFFERENTIAL DIAGNOSIS
• Renal tumor
• Pyelonephrosis
• Renal abscess
• Renal lymphoma
• TB
TREATMENT
GENERAL MEASURES
• Antibiotics, culture specific if possible continued until urine cultures are negative
• Usually managed by nephrectomy
• Partial nephrectomy with rare segmental cases
• Even less, reports of endoscopic treatment with stone removal, drainage continued antibiotics
• In cases of nephrectomy or partial nephrectomy, tissue culture should be used to guide antibiotic therapy
MEDICATION
First Line
• Broad-spectrum antibiotics pending urine culture, such as ampicillin 1 g q8h and an aminoglycoside (ie, gentamicin 5 mg/kg q24h) are usually effective until culture-specific antibiotics can be initiated.
• Negative urine cultures are common, and tissue cultures taken at the time of surgery may be necessary to identify the offending organism.
• Some recommend continuing oral antibiotics for up to 1 wk following nephrectomy.
Second Line
N/A
SURGERY/OTHER PROCEDURES
• Nephrectomy is the most common treatment
– Diffuse inflammatory process
– Nonfunctioning kidney
– Concern for malignancy
– Inflammatory reaction, nephrectomy can be technically difficult
• Partial nephrectomy in rare cases of segmental XGP
• Mechanical and antibiotic bowel prep is performed since XGP may involve any adjacent organs or tissues
– Drains should be placed in renal bed
• Laparoscopic nephrectomy has been shown to be safe without increasing complications but, again difficult (6)
ADDITIONAL TREATMENT
Radiation Therapy
N/A
Additional Therapies
Percutaneous drainage with antibiotics (7)
Complementary & Alternative Therapies
N/A
ONGOING CARE
PROGNOSIS
• Preservation of renal function related to the function of the contralateral kidney
• Recurrence in the contralateral kidney is very rare
• Chance of recurrent stones is high
COMPLICATIONS
• Postoperative respiratory complications
• Wound infection
• An injury to adjacent organs can occur during nephrectomy
• Major vascular injury related to the inflammatory process
• Fistulas or abscesses postoperatively require drainage and antibiotic therapy
• Renal insufficiency related to the function of the contralateral kidney
• Recurrent stone formation
FOLLOW-UP
Patient Monitoring
• Urinalysis and urine culture
• Serum creatinine, CBC, liver enzymes repeated to follow for normalization
• Further radiographic studies depending upon the histopathology of the kidney specimen
Patient Resources
N/A
REFERENCES
1. Kim SW, Yoon BI, Ha US, et al. Xanthogranulomatous pyelonephritis. Clinical experience with 21 cases. J Infect Chemother. 2013;19(6):1221–1224.
2. Korkes F, Favoretto RL, Bróglio M, et al. Xanthogranulomatous pyelonephritis. Clinical experience with 41 cases. Urology. 2008;71:178–180.
3. Dwivedi US, Goyal NK, Saxena V, et al. Xanthogranulomatous pyelonephritis: Our experience with review of published reports. ANZ J Surg. 2006;76:1007–1009.
4. Loffroy R, Guiu B, Watfa J, et al. Xanthogranulomatous pyelonephritis in adults: Clinical and radiological findings in diffuse and focal forms. Clin Radiol. 2007;52:884–890.
5. Zorzos I, Moutzouris V, Korakianitis G, et al. Analysis of 39 cases of xanthogranulomatous pyelonephritis with emphasis on CT findings. Scand J Urol Nephrol. 2003;37:342–347.
6. Shah KJ, Ganpule AP, Kurien A, et al. Laparoscopic vs. open nephrectomy for xanthogranulomatous pyelonephritis: An outcome analysis. Indian J Urol. 2011;27:470–474.
7. Ergun T, Akin A, Lakadamyali H. Stage III xanthogranulomatous pyelonephritis treated with antibiotic therapy and percutaneous drainage. JBR-BTR. 2011;94(4):209–211.
ADDITIONAL READING
Goyal S, Gupta M, Goyal R. Xanthogranulomatous pyelonephritis: A rare entity. N Am J Med Sci. 2011;3(5):249–250.
See Also (Topic, Algorithm, Media)
• Pyelonephritis, Acute, Adult
• Pyelonephritis, Acute, Pediatric
• Pyelonephritis, Xanthogranulomatous Image 
• Renal Mass
• Urinary Tract Infection (UTI), Complicated, Adult
• Urolithiasis, Renal
CODES
ICD9
• 041.6 Proteus (mirabilis) (morganii) infection in conditions classified elsewhere and of unspecified site
• 590.00 Chronic pyelonephritis without lesion of renal medullary necrosis
• 599.60 Urinary obstruction, unspecified
ICD10
• B96.4 Proteus (mirabilis) (morganii) causing dis classd elswhr
• N11.8 Other chronic tubulo-interstitial nephritis
• N13.9 Obstructive and reflux uropathy, unspecified
CLINICAL/SURGICAL PEARLS
• Be suspicious in patients with fever, flank pain, and weight loss.
• Persistent UTI with adequate treatment is a warning.
• CT scan for diagnosis and extent of disease.
• XGP is primarily a surgically managed disease usually by nephrectomy with antibiotics critical to the management of this condition.
• Usually unilateral and frequently confused clinically and radiographically with renal cell carcinoma.