Xanthogranulomatous pyelonephritis: MRI findings in the diffuse and the focal type

Atypical Clinical Presentation of Xanthogranulomatous Pyelonephritis in a Female Child: A Case Report

Xanthogranulomatous pyelonephritis (XGPN) is an uncommon chronic obstructive renal suppuration disease. Histopathologically, XGPN manifests as lipid-laden macrophage infiltration in renal microstructure and inflammation of an engorged non-functional kidney. Nephrectomy is the standard therapeutic treatment, and the overall prognosis is good. Here, we report a case of XGPN presented as flank pain in an otherwise healthy child.

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

Xanthogranulomatous Pyelonephritis (XGP) is a rare, chronic granulomatous inflammatory condition thought to arise secondary to a combination of obstruction, recurrent bacterial infection and an incomplete immune response resulting in focal or diffuse renal destruction. This destruction may be profound with the potential to infiltrate surrounding tissues and viscera. The imaging features of XGP can be ambiguous, mimicking malignancy, tuberculosis (TB) and malakoplakia earning the title of "the great imitator". Computed tomography (CT) is the mainstay of XGP diagnosis and staging, accurately quantifying the stone burden and staging the renal destruction, including the extent of extra-renal spread. Although some cases in children have been successfully treated with antibiotics alone, nephrectomy remains the most common treatment for XGP in adults. The specific management strategy needs to be tailored to individual patients given the potential constellation of renal and extrarenal abnormalities. Although XGP has classically required open nephrectomy, laparoscopic nephrectomy has an increasing role to play arising from the advancement in laparoscopic skills, technique and instruments. Nephron-sparing partial nephrectomy may be considered in the focal form. Interventional radiology techniques most often play a supportive role, eg, in the initial drainage of associated abscesses, but have rarely achieved renal salvage. This narrative review seeks to synthesise the existing literature and summarise the radiological approach and interventional radiology management situated in a clinical context.

Xanthogranulomatous pyelonephritis presenting as a cystic mass: a rare case report

Xanthogranulomatous pyelonephritis may, rarely, occur as a renal cystic mass. We report a case report of a 50-year-old with a history of medically treated renal lithiasis, who consults for left low back pain. Imaging findings concluded to a Bosniak type-3 hemorrhagic cystic mass of the left kidney. The diagnosis of xanthogranumolatous pyelonephritis on its focal form was made histologically. The diagnosis of xanthogranulomatous pyelonephritis is often difficult even with surgical findings and frequently a histological surprise. This points out the importance of identifying it in pre-operative staging; the diagnosis may be suggested by the association of chronic pyelonephritis, renal stones and hypovascular renal tumor syndrome without specificity at sonography and CT.

A Case of Xanthogranulomatous Pyelonephritis with Nephropleural Fistula Formation: Role of MRI in Diagnosis and Treatment

Xanthogranulomatous pyelonephritis (XGP) is a rare type of chronic bacterial nephritis, which rarely involves the invasion of adjacent organs or the formation of fistulas due to tissue-destructive granulomatous reactions. Although the invasions of various adjacent organs have been reported in several cases of XGP, MRI data on their features are limited. MRI has a better soft-tissue resolution than CT. Thus, it can identify the extent of extrarenal involvement in advanced XGP, and the findings can be used in treatment planning. Herein, we report a rare case of XGP with nephropleural fistula formation diagnosed using CT and MRI.

Complicated pyelonephritis associated with chronic renal stone disease

Purpose

This article reviews imaging manifestations of complicated pyelonephritis associated with chronic renal stones disease, in particular xanthogranulomatous pyelonephritis (XGP) and emphysematous pyelonephritis (EPN), as potential mimics of other renal diseases and malignances and provides helpful tips and differentiating features that may alert the radiologist to suspect a diagnosis of infection.

Materials and methods

A retrospective review of the records from 6 adult patients (5 females and 1 male, mean age 72,3 years) with diagnosis of XGP associated with chronic nephrolithiasis and 7 adult patients (6 females and 1 male, mean age 59,3 years) with diagnosis of EPN associated with chronic nephrolithiasis from January 2010 to January 2020 was carried out. Computed tomography urography (CTU) with at least an unenhanced scan, and the parenchymal and excretory phases after contrast medium administration performed at our Teaching Hospital were included. When available images related to conventional radiography, ultrasound (US) and magnetic resonance imaging of the same patients, the comparison with CTU images was carried out.

Conclusion

A possible diagnosis of XGP or EPN must always be taken into account when a pyelonephritis is associated with untreated kidney stones, especially whenever clinical presentation is atypical, current therapy is not effective and imaging shows features of dubious interpretation. Due to their rarity and atypical presentation, a multidisciplinary approach is required and an expert radiologist represents a key figure in the multidisciplinary team as he can help to differentiate between benign and malignant lesions and thus avoid unnecessary radical surgical procedures.

Focal Xanthogranulomatous Pyelonephritis Associated with Xanthogranulomatous Cholecystitis: A Case Report

Xanthogranulomatous inflammation is a rare inflammatory reaction, characterized by lipid-laden macrophages, known as xanthomas, in histopathologic examination. Aggressive xanthogranulomatous inflammation often manifests as local infiltration but does not affect distant organs unless combined with rare systemic diseases. We report a case of focal xanthogranulomatous pyelonephritis (XGP) associated with severe xanthogranulomatous cholecystitis. Focal XGP was suspected in radiologic examination that showed a cystic lesion with an infiltrative margin, which were surgically resected and confirmed in pathologic examination. To our knowledge, this is the first report of focal xanthogranulomatous pyelonephritis associated with xanthogranulomatous cholecystitis. Moreover, we found peripheral hypointensity around the cystic lesion in the T2-weighted image, probably reflecting hemorrhage and fibrosis of the xanthogranulomatous inflammation.

Bear Paw Sign: Xanthogranulomatous Pyelonephritis

Xanthogranulomatous pyelonephritis is a rare form of chronic pyelonephritis in which the involved areas of the kidneys are destroyed and replaced by foam cells. It usually occurs in immunocompromised middle-aged females with ureteral obstruction or chronic urinary tract infection induced by the formation of renal stones. We herein report the case of a 44-year-old woman, with a history of left kidney staghorn calculi and recurrent urinary tract infections. Abdominal computed tomography showed the 'bear paw' sign, typical appearance of XGP and patient underwent a nephrectomy with uneventful post-operative course.

Magnetic resonance imaging (MRI) of the renal sinus

This article presents methods to improve MR imaging approach of disorders of the renal sinus which are relatively uncommon and can be technically challenging. Multi-planar Single-shot T2-weighted (T2W) Fast Spin-Echo sequences are recommended to optimally assess anatomic relations of disease. Multi-planar 3D-T1W Gradient Recalled Echo imaging before and after Gadolinium administration depicts the presence and type of enhancement and relation to arterial, venous, and collecting system structures. To improve urographic phase MRI, concentrated Gadolinium in the collecting systems should be diluted. Diffusion-Weighted Imaging (DWI) should be performed before Gadolinium administration to minimize T2* effects. Renal sinus cysts are common but can occasionally be confused for dilated collecting system or calyceal diverticula, with the latter communicating with the collecting system and filling on urographic phase imaging. Vascular lesions (e.g., aneurysm, fistulas) may mimic cystic (or solid) lesions on non-enhanced MRI but can be suspected by noting similar signal intensity to the blood pool and diagnosis can be confirmed with MR angiogram/venogram. Multilocular cystic nephroma commonly extends to the renal sinus, however, to date are indistinguishable from cystic renal cell carcinoma (RCC). Solid hilar tumors are most commonly RCC and urothelial cell carcinoma (UCC). Hilar RCC are heterogeneous, hypervascular with epicenter in the renal cortex compared to UCC which are centered in the collecting system, homogeneously hypovascular, and show profound restricted diffusion. Diagnosis of renal sinus invasion in RCC is critically important as it is the most common imaging cause of pre-operative under-staging of disease. Fat is a normal component of the renal sinus; however, amount of sinus fat correlates with cardiovascular disease and is also seen in lipomatosis. Fat-containing hilar lesions include lipomas, angiomyolipomas, and less commonly other tumors which engulf sinus fat. Mesenchymal hilar tumors are rare. MR imaging diagnosis is generally not possible, although anatomic relations should be described to guide diagnosis by percutaneous biopsy or surgery.

Infectious and Inflammatory Diseases of the Urinary Tract: Role of MR Imaging

Urinary tract infection (UTI) is among the most common of bacterial infections. Imaging studies are only required in cases of complicated UTIs. Ultrasound remains the first-line imaging method; however, CT is the gold standard for evaluation of UTIs. MR imaging's improved contrast resolution and absence of ionizing radiation may recommend its use for assessment of lower UTIs. Furthermore, MR imaging performs with diagnostic accuracy at least similar to CT in complicated UTIs, except for the identification of calculi and emphysematous pyelonephritis. In this article, the role of MR imaging for the evaluation of infectious and inflammatory disease processes of the urinary tract is reviewed.

Xantogranulomatous pyeloneprhritis in children

Abstract

Xanthogranulomatous pyelonephritis (XPN) is an unusual and severe form of chronic inflammatory lesion of the kidney, characterised by the destruction of the renal parenchyma and the presence of multinucleated giant cells and lipid-laden macrophages, inflammatory infiltration and intensive renal fibrosis. There are a few cases in the literature which describe the disease in children. The pathomechanism of XPN is poorly understood. Renal obstruction with concomitant urinary tract infection is the most commonly associated pathological finding. The process is typically unilateral and may be focal or diffuse. In both cases, the perirenal infiltration is possible and can be mistaken for common renal neoplasm or inflammatory process. The symptoms are non-specific. Diagnostic imaging techniques with clinical suspicion have enabled XPN to be diagnosed and differentiated from malignancy with a high degree of confidence. Computed tomography (CT) is the mainstay of diagnostic imaging. The definitive diagnosis of XPN is based on pathological assessment after nephrectomy. We review and illustrate the clinical, radiological, surgical and pathological characteristics of XPN in children. All cases shown are surgically and histopathologically proven.

Teaching Points

• XPN can present different clinical manifestations.

• CT is the mainstay of diagnostic imaging in XPN.

• Focal type of XPN should be included in the differential diagnosis of children with a renal mass.

• There are no clear guidelines on the management of XPN.

• Conservative and surgical treatments should be considered for each individual case.

• Histopathological examination confirms the diagnosis and excludes other benign and malign diseases.

Spectrum of Xanthogranulomatous Processes in the Abdomen and Pelvis: A Pictorial Review of Infectious, Inflammatory, and Proliferative Responses

OBJECTIVE

Xanthogranulomatous (XG) processes are rare inflammatory conditions with the characteristic pathologic feature of lipid-laden macrophages or histiocyte cells. Imaging findings are nonspecific and can simulate aggressive neoplastic processes. XG processes can be caused by infection, inflammation, histolytic process, or an inherited lysosomal disorder. XG infectious processes are mainly seen in cholecystitis and pyelonephritis, but several other organs can also be involved. Histiocytic processes can be divided into Langerhans and non-Langerhans cell histiocytosis. The non-Langerhans cell histiocytosis entities include Erdheim-Chester disease, Rosai-Dorfman disease, juvenile xanthogranuloma, and hemophagocytic lymphohistiocytosis. The inherited lysosomal disorders resulting in XG processes include Nieman-Pick, Gaucher, and other lysosomal storage disorders.

CONCLUSION

Radiologists need to be able to recognize features of xanthogranulomatous processes to help facilitate patient management.

Case report: Xanthogranulomutous pyelonephritis presenting as "Wilms' tumor"

Background

Xanthogranulomatous pyelonephritis (XGP) is a rare renal tumor that arises as a complication of chronic obstructive pyelonephritis of uncertain etiology. It is primarily an adult tumor seen occasionally in children associated with urinary tract obstruction due to congenital urological anomalies, nephrolithiasis, and recurrent urinary tract infections. Radiologically, it may show neoplastic features such as those seen in common pediatric renal malignancies like wilms’ tumor and renal cell carcinoma. This overlap in radiological manifestation frequently leads to misdiagnosis and delay in appropriate intervention. We report a case of a 3 years old boy who presented with history of recurrent urinary tract infections and a left renal mass initially thought to be Wilms’ tumor.

Case presentation

We present a case of a 3 years old boy admitted to the Pediatric oncology unit at Muhimbli National Hospital in Dar es Salaam, Tanzania with one year history of recurrent fever and urinary tract infection signs and symptoms refractory to antibiotic therapy. He was eventually found to have a left kidney mass detected at the District hospital by abdominal ultrasound performed to evaluate a flank mass that was felt by his mother. He was then referred to our unit for a suspicion of Wilms’ tumor which finally turned out  to be a left kidney Xanthogranulomatous pyelonephritis.

He underwent a successful left nephrectomy and was discharged from hospital in a stable clinical condition and remains asymptomatic at the time of submission of this case report.

Conclusion

This case report underscores the need for clinicians attending a febrile child with a renal mass that can be confused with common pediatric renal malignancies such as Wilms’ tumor to broaden their differential diagnosis. The case also underlines the significance of individualized patient evaluation because this patient would have otherwise received preoperative chemotherapy under the International Society of Pediatric Oncology (SIOP) guidelines if the diagnosis of Wilms tumor was not ruled out.

Sarcoidosis manifesting as a pseudotumorous renal mass

A 53 year-old African American woman with a three-year history of pulmonary sarcoidosis had a follow-up computed tomographic scan to evaluate the status of her disease and response to treatment. On the scan, an abnormal, hypodense mass on the left renal superior pole, which was not present on previous scans, was incidentally discovered. The initial concern was of carcinoma, despite her lack of any urinary symptoms. She underwent further evaluation with magnetic resonance, and the enhancement pattern and the shape of the mass were more suggestive of lymphoma or infarction than a carcinoma. A review of literature revealed sparse case reports demonstrating sarcoidosis presenting as infiltrative granulomatous masses resembling tumors with nonspecific imaging qualities. This diagnosis was entertained and then proven by biopsy. Pseudotumorous renal sarcoid should be in the differential of renal masses, especially in patients with a history of sarcoidosis, as it alters clinical management.

Xanthogranulomatous prostatitis: a rare entity resembling prostate adenocarcinoma with magnetic resonance image picture

Granulomatous prostatitis, characterized by chronic granulomatous inflammation in the prostate, is rare. Xanthogranulomatous prostatitis is an even rarer granulomatous inflammation. We present a 74-year-old man who presented with lower urinary tract symptoms and elevated prostate specific antigen. A transrectal ultrasonography-guided prostate biopsy was performed, and pathological results showed foamy macrophage and inflammatory cell infiltrates, which were a distinctive feature of xanthogranulomatous prostatitis. We also present the characteristics of magnetic resonance imaging in xanthogranulomatous prostatitis which has never been previously described.

Fever of unknown origin (FUO) and a renal mass: renal cell carcinoma, renal tuberculosis, renal malakoplakia, or xanthogranulomatous pyelonephritis?

Often patients with fevers of unknown origin (FUOs) present with loss of appetite, weight loss, and night sweats, without localizing signs. Some are found to have a renal mass during diagnostic evaluation. In patients with FUOs and a renal mass, the differential diagnosis includes renal tuberculosis, renal cell carcinoma (hypernephroma), renal malakoplakia, and xanthogranulomatous pyelonephritis. A 68-year-old woman presented with an FUO during her diagnostic workup. She manifested an irregularly enlarged kidney on abdominal computed tomography (CT) scan, as well as a highly elevated erythrocyte sedimentation rate of more than 100 mm/hour, an elevated serum ferritin level, and chronic thrombocytosis, which favored a diagnosis of renal cell carcinoma. Renal malakoplakia and renal tuberculosis comprised further differential diagnostic considerations. Microscopic hematuria may be present with any of the disorders in the differential diagnosis, but was absent in this case. An abdominal CT scan was suggestive of xanthogranulomatous pyelonephritis. Because of concerns regarding renal cell carcinoma, the patient received a nephrectomy. The pathologic diagnosis was of xanthogranulomatous pyelonephritis, without renal cell carcinoma.

Assessment and characterisation of common renal masses with CT and MRI

Objective

Owing to the widespread use of abdominal imaging studies the detection rate of solid renal masses has increased, and an accurate characterisation of imaging features of renal masses has become more essential for case management.

Method and results

MR imaging (MRI) and computed tomography (CT) are frequently used modalities for detection and differentiation of renal masses. This article gives a review of imaging characteristics of benign and malignant renal masses, discussing their appearance in CT and MR imaging. Advanced MR techniques like diffusion-weighted imaging and apparent diffusion coefficient (ADC) mapping, which have shown promising results in the differentiation between benign and malignant renal lesions, will be introduced.

Conclusion

MRI and CT are useful in the characterisation and estimation of the prognosis for renal masses.

Xanthogranulomatous pyelonephritis in children: diagnostic and therapeutic aspects

Xanthogranulomatous pyelonephritis (XGP) is a rare, chronic inflammatory disease of the kidneys. It is characterized by destruction of renal parenchyma and accumulation of lipid-laden foamy macrophages. Diffuse and focal forms are known. The condition is mainly observed in middle-aged women, and it is very rare in childhood. Of 32 nephrectomies carried out in children for various diseases in our hospital over the course of 2 years, there were two cases of diffuse XGP. In both cases, the preoperative diagnosis based on ultrasound findings was highly suggestive of XGP. We present the two cases and define the typical ultrasonographic signs for distinguishing XGP from other renal masses. The diagnostic and therapeutic management is discussed and an overview of the literature is given.

Neurenteric cyst with xanthomatous changes in the prepontine area: unusual radiological findings

Preoperative diagnosis of neurenteric cysts can be difficult because the imaging findings of a neurenteric cyst may be similar to those of an arachnoid cyst. The authors report a case of a neurenteric cyst with xanthomatous changes in the prepontine area. This 4-year-old girl was admitted to their institution with intermittent neck pain and vomiting. Computed tomography showed a hypodense mass in the prepontine area. Magnetic resonance imaging showed a cystic lesion measuring approximately 4 x 3 cm. The brainstem was displaced posteriorly, and the cisterns in both cerebellopontine angles were widened. The signal intensity of the cyst was similar to that of cerebrospinal fluid. Adjacent to the basilar artery there was a solid component of the mass that enhanced after administration of Gd. Intraoperatively, the authors found a cystic mass containing clear fluid with a yellowish solid nodule. On the basis of histopathological findings, the lesion was diagnosed as a neurenteric cyst with xanthomatous changes.

MR imaging of renal masses: correlation with findings at surgery and pathologic analysis

Magnetic resonance (MR) imaging is useful in the characterization of renal masses. The MR imaging manifestations and pathologic diagnoses of 82 renal masses were reviewed and correlated. The MR imaging appearance of clear cell type renal cell carcinoma varies depending on the presence of cystic components, hemorrhage, and necrosis. Papillary renal cell carcinomas appear as well-encapsulated masses with homogeneous low signal intensity on T2-weighted images and homogeneous low-level enhancement after the intravenous administration of contrast material, or as cystic hemorrhagic masses with peripheral enhancing papillary projections. Transitional cell carcinoma may be seen as an irregular, enhancing filling defect in the pelvicaliceal system or ureter. Lymphomatous masses are usually hypointense relative to the renal cortex on T2-weighted images and enhance minimally on delayed gadolinium-enhanced images. Bulk fat is a distinguishing feature of angiomyolipoma. Oncocytoma has a variable and nonspecific appearance at MR imaging. MR imaging findings may allow the characterization of various renal masses and can provide valuable information for their clinical management.

[Imaging features of xanthogranulomatous pyelonephritis]

Pseudotumoral xanthogranulomatous pyelonephritis is a rare chronic renal infection. Preoperative diagnosis is difficult because of its non-specific presentation. The purpose of this retrospective review of 8 cases is to assess the value of different imaging techniques in the evaluation of this pathology. Six males and 2 females, aged 29 to 75 years were included. The right kidney was involved in 5 cases and the left kidney was involved in 3 cases. Involvement was upper polar in 2 cases and lower polar in 6 cases. A kidney stone was present in 3 cases. US showed a heterogeneous hypoechoic lesion in 3 cases, a homogeneous hypoechoic lesion in 3 cases, and isoechoic lesion in 1 case and a cystic lesion in 1 case. CT showed a focal solid lesion with peripheral enhancement in 4 cases and a cystic mass with peripheral enhancement in 3 cases. US features are non-specific. CT shows a non-specific renal mass, the presence of obstruction and demonstrates perirenal involvement. Preoperative MRI, not performed in our patient population, demonstrates specific changes in the perirenal fat that suggests the diagnosis. The diagnosis of pseudotumoral xanthogranulomatous pyelonephritis can be suspected on a constellation of clinical and laboratory findings combined with non-specific features on CT and US and specific MRI features of perirenal fat changes. Percutaneous biopsy may be needed in selected cases to confirm diagnosis.

Ultrasonographic features of focal xanthogranulomatous pyelonephritis

OBJECTIVE

To analyze the ultrasonographic features of focal xanthogranulomatous pyelonephritis.

METHODS

Ultrasonographic features of 15 patients with pathologically proved focal xanthogranulomatous pyelonephritis were retrospectively analyzed by 2 radiologists who reached a consensus, in terms of the location, margin, size, and echo texture of the mass, associated calculi, lymphadenopathy, or local extension, in comparison with computed tomographic and clinical findings.

RESULTS

At ultrasonography, 12 (80%) of 15 masses were well circumscribed. The maximal sizes of the masses ranged from 2.5 to 5.8 (mean, 3.8) cm. Thirteen solid masses (87%) were hyperechoic (n = 7), hypoechoic (n = 4), or isoechoic (n = 4) to the renal cortex, and the preoperative diagnosis was either renal cell carcinoma (n = 11) or Wilms tumor (n = 2). The preoperative diagnosis of the other 2 cystic lesions (13%) was renal abscess. Renal calculi were found in 1 case, but lymphadenopathy or local extension was not depicted. Clinical inflammatory signs were found in 11 of 15 patients.

CONCLUSIONS

There were no specific ultrasonographic features that allow for the distinction between focal xanthogranulomatous pyelonephritis and renal tumors or abscesses. Focal xanthogranulomatous pyelonephritis should be considered when there are clinical signs of infection or inflammation and a focal solid mass is seen on ultrasonography.

Radiologic evaluation of patients with renal infections

Although renal imaging is not indicated routinely in cases of uncomplicated renal infection, CT is a highly sensitive modality to diagnose and guide the management of patients with acute renal infection. CT is particularly useful in identifying complications of renal infection. Intravenous urography and US are limited to screening for urinary obstruction, renal calculi, and underlying anomalies. CT is also of value in establishing the diagnosis in equivocal cases, in evaluating high-risk patients, and in determining the nature and extent of disease. CT urography is increasingly performed as a comprehensive urinary tract imaging study. MRI may be performed when patients have contraindications to iodinated contrast material. Cortical scintigraphy is the preferred imaging study for the evaluation of children with acute pyelonephritis, although power Doppler US can be considered as a possible alternative. Recent limited studies using gadolinium-enhanced MRI have been shown to be valuable in the depiction of changes of acute pyelonephritis.

Pediatric focal xanthogranulomatous pyelonephritis: dynamic contrast-enhanced MRI findings

Xanthogranulomatous pyelonephritis (XPN) is the result of chronic renal infection. It is very rare in childhood and the focal form, which is said to be more common in children, is often misdiagnosed as a renal tumor. We report a case of a focal XPN in a 14-year-old girl. The true preoperative diagnosis may be very hard in children especially in the focal form but it seems to be possible by the help of dynamic contrast-enhanced MRI.

US and CT findings of xanthogranulomatous pyelonephritis

Ultrasonographic and computed tomographic findings of 21 cases of pathologically proven xanthogranulomatous pyelonephritis (XGP) in 20 patients were retrospectively evaluated. Seventeen (81%) were diffuse, and extrarenal extension occurred in 13 cases (62%). The kidney was enlarged diffusely in 12 cases (57%), and focally in 3 (14%). Urinary calculi were present in 16 cases (76%), with staghorn calculi in 4 of these, and hydronephrosis occurred in 17 (81%). In addition to typical features of XGP, the condition may also show variable imaging findings.