eMedicine Specialties > Urology > Infections and Related Inflammatory Conditions

Xanthogranulomatous Pyelonephritis

Author: Joe D Mobley III, MD, MPH, Resident Physician, Department of Surgery, Division of Urology, University of Tennessee Graduate School of Medicine/University of Tennessee Medical Center
Coauthor(s): Scott Rutchik, MD, Assistant Professor, Department of Surgery, Division of Urology, University of Connecticut School of Medicine
Contributor Information and Disclosures

Updated: Jun 11, 2008

Introduction

Xanthogranulomatous pyelonephritis (XGP) is a rare, serious, debilitating illness characterized by an infectious renal phlegmon. This disease process ultimately results in focal or diffuse renal destruction and is characterized pathologically by lipid-laden foamy macrophages. XGP shares many characteristics with true renal neoplasms in terms of its radiographic appearance and ability to involve adjacent structures or organs. Most cases of XGP are unilateral and are often associated with urinary tract obstruction, infection, nephrolithiasis, diabetes, and/or immunocompromise. The treatment of XGP is almost universally extirpative and can pose a formidable challenge to the surgeon.

History of the Procedure

Schlagenhaufer first described XGP in 1916. The first pediatric case was not described until 1963. Historically, open extirpative therapy has been the hallmark of management, although an increasing number of reports have recently described successful laparoscopic intervention. 

Problem

XGP is defined as a chronic inflammatory disorder of the kidney characterized by a destructive mass that invades the renal parenchyma. The condition is most commonly associated with Proteus or Escherichia coli infection. Pseudomonas species have also been implicated. The kidney is usually nonfunctional. Most cases of XGP involve a diffuse process; however, up to 20% are focal. 

Although most cases of XGP are unilateral, bilateral disease has been reported. Bilateral nephrectomy and long-term dialysis is a treatment option. Although Perez et al described successful treatment with partial nephrectomies in one patient,¹ bilateral XGP is usually fatal.

Frequency

XGP occurs in approximately 1% of all renal infections. Although XGP is rare in the pediatric population, it is found in approximately 16% of pediatric nephrectomy specimens. XGP is 4 times more common in women than in men and is usually noted in the fifth and sixth decades of life. XGP affects both kidneys with equal frequency.

Etiology

The exact etiology of XGP is unknown, but it is generally accepted that the disease process requires long-term renal obstruction and infection. Stones (frequently of staghorn proportions) develop in 80% of patients with XGP but are not required to make the diagnosis. XGP is often observed in patients with diabetes and/or immunocompromise. Abnormal lipid metabolism has also been hypothesized as an etiologic factor in individuals with XGP.

Pathophysiology

XGP displays neoplasmlike properties capable of local tissue invasion and destruction and has been referred to as a pseudotumor. Adjacent organs, including the spleen, pancreas, or duodenum, may be involved. 

The gross appearance of XGP is a mass of yellow tissue with regional necrosis and hemorrhage, superficially resembling renal cell carcinoma. The pathognomonic microscopic feature is the lipid-laden foamy macrophage accompanied by both chronic- and acute-phase inflammatory cells. Focal abscesses may be observed.

Presentation

Patients with XGP often appear chronically ill. Symptoms include anorexia, fever, chills, weight loss, and flank pain. The pain of XGP is not colicky in nature; it is usually dull and persistent. Urine typically contains both leukocytes and bacteria. The pH is often basic because Proteus mirabilis is a urease-producing organism. The erythrocyte sedimentation rate is frequently elevated.

XGP is notorious for fistulization. Pyelocutaneous and ureterocutaneous fistulae have been well-described. Other organs are occasionally involved in this process, including surrounding viscera with resulting pyeloenteric fistulae.

In children, XGP is more common in boys and usually affects those younger than 8 years. Obstruction associated with XGP in the pediatric population is more due to congenital factors than obstructive calculi.

Renal cell carcinoma may be indistinguishable from XGP radiographically and clinically. A case of XGP involving thrombus of the renal vein has been reported.² XGP and renal cell carcinoma have even been observed in the same specimen. Shah et al have reported a mistaken diagnosis of renal XGP that was subsequently proven to be renal tuberculosis.³ XGP must be diagnosed based on histology rather than based solely on radiographic imaging studies.

Illustrating the varied presentation of XGP, a recent case report by Hitti et al describes XGP located in a renal allograft.⁴ Another recent report describes a case of XGP associated with psoas abscess in a young pregnant woman in her third trimester.⁵

Indications

Xanthogranulomatous pyelonephritis (XGP) is a surgically managed disease requiring either nephrectomy or, in rare circumstances, partial nephrectomy. Extirpation is necessary because the disease occurs or results in an infected, nonfunctioning kidney.

Relevant Anatomy

The kidneys are paired organs in the retroperitoneum. They are covered in a thin, fibrous capsule that is in turn covered by Gerota fascia. On the right, the liver and adrenal gland abut the superior pole of the kidney. The second part of the duodenum is medial to the right kidney and may be reflected medially to gain exposure to the inferior vena cava (Kocher maneuver). On the left, the superior pole of the kidney is attached to the spleen superolaterally (splenorenal ligament) and is very near to or in direct contact with the tail of the pancreas medially.

The colon is anterior to the kidneys and is easily reflected anteriorly and medially when transabdominal exposure is required. The renal hilar structure from anterior to posterior includes the vein, artery, and collecting system. The left renal vein has 3 draining tributaries, ie, the adrenal, gonadal, and posterior lumbar veins.

Contraindications

Contraindications to surgical therapy of xanthogranulomatous pyelonephritis (XGP) are those consistent with all major operations and intolerance to anesthesia, uncorrected coagulopathy, and severe connective-tissue disorders. 

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