Xanthogranulomatous Pyelonephritis: A Narrative Review with Current Perspectives on Diagnostic Imaging and Management, Including Interventional Radiology Techniques

Imaging and Clinical Findings of Xanthogranulomatous Inflammatory Disease of Various Abdominal and Pelvic Organs: A Pictorial Essay

Xanthogranulomatous (XG) inflammatory disease is a rare benign disease involving various organs, including the gallbladder, bile duct, pancreas, spleen, stomach, small bowel, colon, appendix, kidney, adrenal gland, urachus, urinary bladder, retroperitoneum, and female genital organs. The imaging features of XG inflammatory disease are nonspecific, usually presenting as a heterogeneous solid or cystic mass. The disease may also extend to adjacent structures. Due to its aggressive nature, it is occasionally misdiagnosed as a malignant neoplasm. Herein, we review the radiological features and clinical manifestations of XG inflammatory diseases in various organs of the abdomen and pelvis.

Tumefactive Nonneoplastic Proliferative Pseudotumors of the Kidneys and Urinary Tract: CT and MRI Findings with Histopathologic Correlation

A diverse spectrum of pathologically distinct, nonneoplastic, proliferative conditions of the kidneys and urinary tract demonstrate a expansile growth pattern similar to that of neoplasms. The renal pseudotumors include myriad causes of infections as well as rare noninfectious causes such as sarcoidosis, amyloidosis, and immunoglobulin G4-related disease (IgG4-RD). Rare entities such as cystitis cystica, endometriosis, nephrogenic adenoma, and pseudosarcomatous myofibroblastic proliferation and distinct types of prostatitis comprise tumefactive nontumorous disorders that affect specific segments of the urinary tract. The pseudotumors of the kidneys and urinary tract demonstrate characteristic histopathologic and epidemiologic features, as well as protean clinical manifestations, natural history, and imaging findings. Many patients present with genitourinary tract-specific symptoms or systemic disease. Some cases may be incidentally discovered at imaging. Some entities such as perinephric myxoid pseudotumors, IgG4-RD, fibroepithelial polyp, and nephrogenic adenoma display specific anatomic localization and disease distribution. Imaging features of multisystem disorders such as tuberculosis, sarcoidosis, and IgG4-RD provide supportive evidence that may allow precise diagnosis. Fungal pyelonephritis, xanthogranulomatous pyelonephritis, IgG4-RD, actinomycosis, and endometriosis show markedly low signal intensity on T2-weighted MR images. Although some pseudotumors exhibit characteristic imaging findings that permit correct diagnosis, laboratory correlation and histopathologic confirmation are required for definitive characterization in most cases. A high index of suspicion is a prerequisite for diagnosis. Accurate diagnosis is critical for instituting optimal management while preventing use of inappropriate therapies or interventions. Surveillance CT and MRI are frequently used for monitoring the response of pseudotumors to therapy. ©RSNA, 2023 Quiz questions for this article are available in the supplemental material.

A pictorial review of genitourinary infections and inflammations

Various infectious and inflammatory diseases affect the genitourinary system. This paper provides a review of multiple common and uncommon infectious and inflammatory conditions affecting the genitourinary system and some associated complications. These include acute infectious cystitis, emphysematous cystitis, acute pyelonephritis, emphysematous pyelonephritis, renal and perinephric abscesses, pyonephrosis, xanthogranulomatous pyelonephritis, epididymo-orchitis, vasitis, prostatitis, pelvic inflammatory disease, renal hydatid infection, renal tuberculosis, actinomycosis, Erdheim-Chester Disease, IgG4-Related Kidney Disease, urethritis and urethral strictures, ureteritis cystica, and genitourinary fistulas. Radiologists should be aware of these diseases' complications and management. Uncommon conditions must be considered when evaluating the genitourinary system.

[Abdominal wall skin nodules revealing xanthogranulomatous pylonephritis]

INTRODUCTION

Xanthogranulomatous pyelonephritis is a chronic pyelonephritis characterized by an inflammatory granulomatous reaction that destroys the renal parenchyma. It is an uncommon entity. Diffuse inflammation has the potential to spread to nearby organs, especially the skin.

OBSERVATION

A 73-year-old patient presented with a three-year history of painful and fistulized nodules on the abdominal wall. The results of abdominal computed tomography and magnetic resonance imaging revealed xanthogranulomatous pyelonephritis with extension to the skin, colon, and psoas muscle. The skin lesions were improved by a double antibiotic therapy. The patient was advised to have a radical left nephrectomy, but he refused surgery and was then lost to follow-up.

CONCLUSION

We report an uncommon case of xanthogranulomatous pyelonephritis revealed by cutaneous nodules of the abdominal wall, with an extension toward the skin, the colon and the psoas muscle.

MDCT Diagnosis and Staging of Xanthogranulomatous Pyelonephritis

Background: Benign nephrectomy to treat patients with renal inflammatory disease in cases of severe urinary infection represents a diagnostic and management challenge because of significant inflammatory, fibrotic, and infectious components. Among renal inflammatory diseases, fistulization and invasiveness to adjacent structures are some of the hallmarks of xanthogranulomatous pyelonephritis (XGP). The aims of this study were as follows 1. to retrospectively determine key demographic and clinical features of XGP among benign nephrectomies; 2. to assess the CT preoperative diagnostic accuracy; and 3. to define the imaging characteristics of the CT stage. Material and Methods: A retrospective review of clinical, laboratory, and radiological features and operative methods of patients who underwent benign nephrectomy with histologically proven XGP was performed. Results: XPG was diagnosed in 18 patients over a 4-year (2018–2022) period. XGP represented 43.90% among benign nephrectomies. The mean age of the patients was 63 years, and the sex prevalence was higher in women (72.22%). Symptoms were vague and not specifically referrable to urinary tract disorders and unilateral (100%), with the left kidney affected in 61.11% of cases. Staghorn calculi and stone disease were the most common underlying cause (72.22%). All patients underwent CT. The preoperative CT imaging accuracy for renal inflammatory disease was 94.44% and indeterminate in 5.56%. A suspected diagnosis of XGP was formulated in 66.67% (12/18; 2 stage II/10 stage III), meanwhile, in 33.33% (6 patients with stage I), a non-specific diagnosis of renal inflammatory disease was formulated. CT was reported according to the Malek and Elder classification and staged in the stage I nephric form (33.33%), stage II perinephric form (11.11%), stage III paranephric form (55.56%). Conclusions: The CT diagnostic accuracy for kidney inflammatory disease was extremely high, whereas the suspected diagnosis of XGP was formulated preoperatively in only 66.67% of high-stage disease, where the hallmarks of invasiveness and fistulization of the pathology increased the diagnostic confidence.

Concurrent Xanthogranulomatous Pyelonephritis and Upper Urinary Tract Transitional Cell Carcinoma

A 37-year-old male with a history of chronic nephrolithiasis presented to the ED with gross hematuria, clot retention, and right flank pain. The patient had radiological findings of perinephric stranding, marked hydronephrosis, and marked thinning of the right renal parenchyma on computed tomography (CT), all suggestive of xanthogranulomatous pyelonephritis (XGP). The specimen following radical nephrectomy revealed urothelial carcinoma (UC) in a background of XGP but with no evidence of spread to regional lymph nodes. Follow-up imaging revealed hypodense lesions in the liver which demonstrated UC on biopsy. This is the first reported case of a young patient presenting with such an advanced stage of UC in the setting of XGP. It illustrates the link between inflammatory processes of the kidney and malignancy of the upper urinary tract.

Magnetic Resonance Imaging Virtual Biopsy of Common Solid Renal Masses-A Pictorial Review

ABSTRACT

The expanded application of radiologic imaging resulted in an increased incidence of renal masses in the recent decade. Clinically, it is difficult to determine the malignant potential of the renal masses, thus resulting in complex management. Image-guided biopsies are the ongoing standard of care to identify molecular variance but are limited by tumor accessibility and heterogeneity. With the evolving importance of individualized cancer therapies, radiomics has displayed promising results in the identification of tumoral mutation status on routine imaging. This article discusses how magnetic resonance imaging features can guide a radiologist toward identifying renal mass characteristics.

Xanthogranulomatous pyelonephritis - A diagnostic and therapeutic dilemma

Xanthogranulomatous pyelonephritis (XGP) is a rare variant of chronic pyelonephritis, occurring in the setting of obstructive uropathy and recurrent urinary tract infections (UTIs). It is difficult to diagnose as it can be asymptomatic until late-stage disease. Localized symptoms such as flank pain and dysuria may be attributed to nephrolithiasis or UTIs without prompting need for further workup. Extrarenal manifestations, most notably fistula formation, may present distal to the kidney and not be readily attributed to a renal pathology. The only known definitive therapy is nephrectomy. A delay in diagnosis can lead to fulminant complications or a more technically difficult nephrectomy. We present three cases of XGP, which serve to highlight the possibility of earlier diagnosis and resultant management options, including the potential for nephron-saving strategies. Early clinical and radiologic suspicion through awareness of risk factors may play an important role in preventing disease progression, avoiding late-stage complications, and improving treatment outcomes.

Focal Xanthogranulomatous Pyelonephritis on FDG PET/CT

ABSTRACT

Xanthogranulomatous pyelonephritis is a rare disease that was often accompanied with urinary obstruction. The focal form of xanthogranulomatous pyelonephritis is frequently misdiagnosed as malignancy. Here we present FDG PET/CT findings of a case focal xanthogranulomatous pyelonephritis in a 66-year-old woman with polycystic liver and kidney disease. The image showed a polycystic mass in the inferior pole of right kidney with high FDG uptake in the cystic wall, which was suggestive of a cystic renal carcinoma. Right radical nephrectomy was subsequently performed. The postsurgical pathology revealed xanthogranulomatous pyelonephritis.

Focal xanthogranulomatous inflammation of the kidney cyst without pyelitis: a rare presentation mimicking kidney cancer

Xanthogranulomatous pyelonephritis (XGP) is one of the most common granulomatous diseases of the kidney. XGP is subdivided into diffuse, segmental, and focal subtypes. Preoperative diagnosis of focal XGP on radiological imaging can be challenging, especially without involvement of the renal pelvis. Here, we report the case of a 61 year-old male with focal xanthogranulomatous inflammation of the kidney without pyelitis. The lesion presented as a mural nodule on the left renal cortical cyst, and kidney cancer was suspected on the preoperative image. The patient underwent a successful partial nephrectomy. Pathological examination revealed that the mural nodule displayed xanthogranulomatous inflammation and was clearly distinct from the renal pelvis. Thus, it should be considered that a mural nodule in a renal cortical cyst could be xanthogranulomatous inflammation.

Case report: Localized xanthogranulomatous pyelonephritis in children: A case report and literature review

BACKGROUND

Xanthogranulomatous pyelonephritis (XGPN), which is featured by inflammatory destruction of renal parenchyma and fibrosis of kidney, occurs mainly among adults, sporadically among children and rarely among infants. Recurrent urinary tract infections, kidney stone-induced obstructive nephropathy, malnutrition, abnormal lipid metabolism, hypoimmunity, lymphatic obstruction and congenital urinary abnormalities may all cause XGPN among children. Its primary treatment is radical nephrectomy.

CASE DESCRIPTION

In this study, we describe a rare case of XGPN in a 7-year-old boy infected with Staphylococcus aureus (S. aureus). The child presented with symptoms including recurrent fever, urine culture negative. The postoperative pathology confirmed XGPN. Besides, partial nephrectomy was performed.

CONCLUSION

XGPN, as a special type of chronic pyelonephritis, is a rare pyelonephritis requiring surgical treatment. Early diagnosis and treatment are crucial to reducing its morbidity and mortality. Although radical nephrectomy is the primary therapeutic option for patients with XGPN, partial nephrectomy surgery should be considered for focal XGPN, aiming to preserve residual renal function in children as far as possible.