Continuing Education Activity

Xanthogranulomatous pyelonephritis is a rare, aggressive variant of pyelonephritis, typically caused by chronic infection and nephrolithiasis. It is believed to occur due to obstructive uropathy that leads to an ongoing cycle of infection and inflammation, ultimately resulting in fibrosis. This condition is characterized by the invasion of renal parenchyma by lipid-laden macrophages, known as xanthoma cells), which causes a characteristic yellowish appearance. Diagnosis can be challenging, often being mistaken for renal cell carcinoma, or, less commonly, malakoplakia. A computed tomography scan and histology of the lesion help to confirm the diagnosis. As it can involve adjacent structures or organs, early diagnosis is essential. As xanthogranulomatous pyelonephritis is often diagnosed after loss of renal function in the affected kidney, accompanied by extensive inflammation and fibrosis, a nephrectomy, either laparoscopic or open, is often required. This activity describes the evaluation and management of xanthogranulomatous pyelonephritis, highlighting the role of the interprofessional team in patient care.

Objectives:

• Identify the most common etiologies of xanthogranulomatous pyelonephritis and the contributing role of nephrolithiasis.

• Determine the diagnostic approach to xanthogranulomatous pyelonephritis using radiology imaging findings along with indications for renal biopsy and microscopic evaluation.

• Select appropriate treatment options for a patient diagnosed with xanthogranulomatous pyelonephritis based on individual patient characteristics, current renal function, and laboratory and diagnostic testing results.

• Collaborate and communicate effectively among the interprofessional team, including urologists, nephrologists, infectious disease specialists, pediatricians, and primary care providers, to enhance the delivery of care and decrease morbidity in patients with xanthogranulomatous pyelonephritis.

Introduction

Xanthogranulomatous pyelonephritis is a rare but aggressive variant of chronic pyelonephritis, resulting in a nonfunctioning kidney. This variant is most often associated with chronic obstruction and renal calculi with ongoing or chronic infection.[1] 

The condition has been known as the great imitator due to its presentations similar to more common conditions and is sometimes called a pseudotumor, as the affected kidney is enlarged and resembles a tumor in its ability to cause local invasion and tissue destruction.[2]

The disease is characterized by the destruction and replacement of renal or perirenal tissue with granulomatous tissue containing lipid-laden macrophages. Xantho is derived from the Greek word xanthós ("yellow") and is used due to the infiltration of yellow lipid-laden macrophages observed in the histological sections. Xanthogranulomatous pyelonephritis was first described by Schlagenhaufer in 1916 and later named xanthogranuloma by Osterlin in 1944.[3][4][5][6]

Xanthogranulomatous pyelonephritis is often confused with a true neoplasm, most commonly renal cell carcinoma, due to its similar clinical and radiographic characteristics and ability to involve adjacent structures or organs. Therefore, early identification and treatment are paramount to decrease the associated morbidity and mortality rates. Although antibiotics can be given for acute infection, the usual treatment for xanthogranulomatous pyelonephritis is a partial or total radical nephrectomy.[7]

Etiology

The precise etiology of xanthogranulomatous pyelonephritis remains unknown, although most cases result from chronic urinary obstruction and urinary tract infection. The organisms most commonly associated with xanthogranulomatous pyelonephritis are Escherichia coli and Proteus mirabilis, followed by Pseudomonas, Enterococcus faecalis, and Klebsiella.[8]

The primary cause of urinary obstruction in xanthogranulomatous pyelonephritis is nephrolithiasis, specifically a staghorn calculus that is present in almost 80% of patients. This calculus serves as a site of infection that progressively destroys the renal parenchyma. However, in children, congenital ureteropelvic junction abnormalities may result in chronic urinary obstruction and predispose to the development of xanthogranulomatous pyelonephritis, as calculi are less common in children.[9][10][11] Other abnormalities predisposing the urinary tract to obstruction, such as ureteropelvic duplication, ureteropelvic junction syndrome, vesicoureteral reflux, and bladder cancer, are also associated with xanthogranulomatous pyelonephritis. These structural abnormalities, along with obstructive nephrolithiasis and recurrent urinary tract infections, are considered major risk factors for xanthogranulomatous pyelonephritis. Additional associated renal conditions include chronic interstitial nephritis, renal cell carcinoma, transitional cell carcinoma, and squamous cell carcinoma.[12]

Risk factors associated with xanthogranulomatous pyelonephritis include the following:

• Abnormal lipid metabolism
• Brachydactyly mental retardation syndrome in children
• Diabetes mellitus
• Hepatitis C
• Hypertension
• Immunocompromised state
• Metabolic syndrome
• Nephrolithiasis
• Recurrent urinary tract infections
• Renal transplantation
• Rheumatoid arthritis
• Ureteropelvic junction obstruction 
• Vesicoureteral reflux [12][13]

Epidemiology

The incidence of xanthogranulomatous pyelonephritis varies from 0.6% to 1% of all renal infections. The disease can occur in all age groups but is more common in women compared to men, typically between ages 45 and 55.[12][14][15] No specific race predilection is present. In most patients, only one kidney is affected, but bilateral involvement can occur rarely. Both sides are affected with equal frequency. 

Xanthogranulomatous pyelonephritis is extremely rare in children but still accounts for 16% of all nephrectomies in the pediatric age group. Children younger than 8 years are affected more often compared to older children.

The overall annual incidence of xanthogranulomatous pyelonephritis has been reported as 1.4 cases per 100,000 population, and up to 4% of patients with chronic pyelonephritis have xanthogranulomatous pyelonephritis.[12][16]

Pathophysiology

The exact pathophysiology of xanthogranulomatous pyelonephritis is unclear. The mechanism involved in its pathogenesis includes nephrolithiasis, which leads to chronic obstruction and infection. About 80% of patients have a staghorn stone, which is not an absolute requirement for diagnosis.

Xanthogranulomatous pyelonephritis is a chronic inflammatory disorder of the kidney that may occur due to a defect in the degradation of bacteria by macrophages or another inadequate host response to chronic infection complicated by obstruction.[17] This process creates a repeating cycle of obstructive uropathy complicated by recurrent infections and worsening inflammation, ultimately resulting in xanthogranulomatous pyelonephritis. More recent research suggests that vimentin may be a key mediator in the fibrotic progression of xanthogranulomatous pyelonephritis.[12]

The disease is characterized by the destruction and replacement of renal or perirenal tissue with granulomatous tissue containing abundant lipid-laden macrophages. These macrophages accumulate when the concentration of intracellular lipids in the macrophage cytoplasm exceeds the cell's ability to maintain homeostasis. Critical immune functions of the affected macrophages are reduced.[18] 

If left untreated, xanthogranulomatous pyelonephritis starts from the renal pelvis and calyces, spreads to the renal parenchyma, and finally to the retroperitoneum and adjacent organs. Common manifestations include the formation of fistulas, deep sinuses, and small abscesses.[19] Adjacent organs such as the liver, spleen, duodenum, pancreas, and great vessels can be involved in severe forms of xanthogranulomatous pyelonephritis.[20]

Histopathology

The microscopic examination of a xanthogranulomatous pyelonephritis lesion shows 3 distinct zones centered around a calyx, with the following findings in each zone.

• Inner zone: Histiocytes, leukocytes, lymphocytes, plasma cells, and macrophages, accompanied by necrosis.

• Middle zone: Granulation tissue surrounded by hemorrhage. The pathognomonic characteristic is the presence of lipid-laden foamy macrophages (xanthoma cells), which give a yellowish color to the affected tissue.

• Outer zone: Giant cells, cholesterol clefts, and fibrous tissues.[21]

Classic findings include the replacement of parenchymal renal tissue with foamy, lipid-laden macrophages (xanthoma cells). Cytoplasm stains positive for vimentin, lysosome, and CD68. A distinguishing characteristic of renal cell carcinoma is that clear cell and papillary cell renal cell carcinoma stain positive for epithelial membrane antigen and CD10.[12]

Xanthogranulomatous pyelonephritis should also be distinguished from malakoplakia, which can have a similar appearance.[12] Malakoplakia is a benign chronic inflammatory process characterized by the presence of Michaelis-Guttman bodies, which are round or oval, basophilic inclusions in the cytoplasm of histiocytes. These bodies stain positively with periodic acid-Schiff stain and are unique to malakoplakia. See the companion StatPearls' reference, "Malakoplakia," for further information.

The gross pathology of the mass appears yellowish and enlarged with areas of necrosis and hemorrhage. An obstructive kidney stone is often associated.[15]

History and Physical

The typical history of a patient with xanthogranulomatous pyelonephritis is that of a middle-aged female who presents with recurrent urinary tract infections, most commonly caused by bacteria such as Escherichia coli or P mirabilis.[22]

In children, presenting complaints may include fever, flank or abdominal pain, and growth retardation. About 50% of cases demonstrate a palpable abdominal mass.

The presentation is similar to renal tuberculosis. Hence, any travel history to an endemic region and risk factors should be evaluated.

Common symptoms in adult patients with xanthogranulomatous pyelonephritis include:

• Flank pain, malaise, and fever are the most common presenting complaints in patients with xanthogranulomatous pyelonephritis. The nature of the flank pain is described as dull and persistent, which is not at all similar to renal colic.
• Urinary symptoms include dysuria, hematuria, and increased urinary frequency.
• Anorexia, chills, malaise, and weight loss have also been reported.[15][23][24][23]

In children, xanthogranulomatous pyelonephritis may appear with two different presentations.

• The more common form involves the entire kidney and affects both sexes equally.
• The less common form includes a localized renal area and primarily affects females.         

Physical findings may include the following:

• Conjunctival pallor due to anemia
• Costovertebral angle tenderness on palpation
• Fever
• Palpable renal mass [12]

In advanced cases of xanthogranulomatous pyelonephritis, extrarenal manifestations can be symptomatic, including the following:

• Cutaneous drainage of a fistula, which is often misdiagnosed as a superficial abscess (not uncommon and associated with delayed diagnosis)
• Hepatomegaly or a perihepatic abscess associated with abdominal pain, nausea, fevers, weakness, or cough
• Splenic involvement causing abdominal pain, fevers, and chills
• Gluteal or psoas abscess causing abdominal pain, fevers, or swelling [12]

Evaluation

Diagnosing a patient with xanthogranulomatous pyelonephritis necessitates a thorough evaluation, including a detailed history, physical examination, comprehensive laboratory work, and imaging studies. However, despite these measures, it is estimated that an accurate diagnosis is achieved preoperatively in only 40% of cases.[25]

The detailed laboratory and radiographic findings are reviewed below.

Laboratory Examination

Laboratory examination includes a complete blood count with a differential that may show anemia and leukocytosis in a patient with xanthogranulomatous pyelonephritis. Erythrocyte sedimentation rate and C-reactive protein are often elevated. Other laboratory signs of infection or sepsis may also be elevated, such as lactic acid, procalcitonin, and neutrophil/lymphocyte ratio.[26][27] 

In a study, patients with xanthogranulomatous pyelonephritis demonstrated abnormal laboratories, including anemia (63%), elevated serum white blood cells (41%), increased erythrocyte sedimentation rate (94%), and pyuria (57%).[14]

Renal function tests may show elevated levels of blood urea nitrogen and creatinine. Treatment options such as nephrectomy may not improve these chemistries.

Liver function tests are often abnormal in about 50% of patients with xanthogranulomatous pyelonephritis due to mild biliary retention.

Urine Examination

Urine examination may show signs of a urinary tract infection, including pyuria, bacteriuria, and hematuria. Proteinuria is common, and urine pH levels may be elevated. Urine cultures frequently show the growth of organisms such as E coli and P mirabilis, but Pseudomonas, E faecalis, Klebsiella, and other bacteria may also be found, or the culture may be negative.[12] The identification of xanthoma cells on urine cytology is specific but not sensitive, being present in only about 30% of cases.[28]

In cases where a percutaneous nephrostomy is performed, a separate urine culture should be prepared on urine obtained from the procedure. Appropriate antibiotics should be administered.

Radiographic Imaging

The classic radiology triad for xanthogranulomatous pyelonephritis includes a unilateral enlarged kidney, a renal pelvis stone, and a nonfunctional or poorly functioning kidney.[29][30][31][32] The contralateral kidney to the xanthogranulomatous pyelonephritis infection may also be enlarged due to hyperfiltration.[12]

X-ray: X-ray of the abdomen, including the kidney, ureter, and bladder, may indicate the presence of calculi, especially staghorn calculi.

Renal ultrasonography: Ultrasonography of the kidneys may reveal hydronephrosis, kidney enlargement, nephrolithiasis, a loss of normal renal architecture, parenchymal thinning, and hypoechoic masses.[29][33] These hypoechoic areas are typically smaller than 20 mm in size and represent small abscesses or xanthogranulomas.[33]

The gall bladder may appear inflamed with increased vascularity and wall thickening. Dilation of the hepatic ducts may also be observed.[33] 

Overall, ultrasound is substantially less sensitive and specific compared to computed tomography (CT) for diagnosing renal masses and generally cannot reliably differentiate xanthogranulomatous pyelonephritis from similar renal inflammatory and neoplastic disorders.[12][34]

Computed tomography scan: A CT scan is the most useful imaging modality for diagnosing xanthogranulomatous pyelonephritis. A noncontrast CT demonstrates any calculi involved, expected in about 80% of patients with xanthogranulomatous pyelonephritis. This technique can also identify renal stones within the collecting system, particularly inside renal masses or pseudotumors.[29][35]

A CT scan with contrast may show replacement of normal renal tissue by multiple hypoechoic areas (15-18 Hounsfield units) representing portions of the dilated collecting system surrounded by an enhancing rim of contrast that causes a multiloculated appearance, known as the bear paw sign.[29][36][30] The bear paw sign is an axial image of the affected kidney showing a dilated renal pelvis and calyces resembling a bear's paw.[29][36][30] Necrotic xanthomatous material often lines the dilated calyces and may extend into the renal parenchyma.[29] 

Thinning of the renal parenchyma and perinephric fat enhancement may be found. Contrast excretion may be poor in the affected kidney due to reduced renal function.[12] A CT scan can also determine the presence and extent of local invasion of the lesion and can be used to stage the disease.

Magnetic resonance imaging: Magnetic resonance imaging (MRI) can be performed in patients allergic to contrast but offers no other advantage over CT scanning.[29][37][38] Young children may find MRI challenging due to the lengthy procedure duration without sedation.

Renal scintigraphy: Renal scintigraphy, or nuclear medicine scans, can be used to determine the relative renal function of each kidney.[39] In about 80% of cases, little or no renal function remains in the affected kidney, simplifying the decision to proceed with a radical nephrectomy once the patient is sufficiently healthy for surgery.[12][40] 

Intravenous urography: Intravenous urography may show a poorly functioning or nonfunctional kidney, although it is not commonly utilized.[41][42]

Positron emission tomography scans: Positron emission tomography (PET) scans do not help differentiate xanthogranulomatous pyelonephritis from clinically similar inflammatory renal conditions or neoplasms.[40] If doubt remains after appropriate imaging, a biopsy may be needed for a definitive diagnosis, especially if it affects treatment.

Renal Biopsy 

Renal biopsy is often required if radiologic studies are not definitive. The pathognomonic finding is lipid-laden foamy macrophages, which can be challenging to differentiate from clear cell carcinoma of the kidney. In cases where differentiation between xanthogranulomatous pyelonephritis and renal cell carcinoma is challenging, patients with xanthogranulomatous pyelonephritis have positive periodic acid-Schiff staining and test positive for CD68, lysozyme, and vimentin.[12][14][16][43][44] On the other hand, renal cell carcinoma tests positive for CD10 and epithelial membrane antigen.[16][44] 

The preoperative diagnosis of xanthogranulomatous pyelonephritis can be challenging due to the similarity of findings compared to renal cell carcinoma. Although a CT scan can help differentiate these two conditions and determine the extent of the disease, only a pathological microscopic examination can definitively confirm the diagnosis in some problematic cases. Arguably, if the treatment is the same (radical nephrectomy), a biopsy to differentiate the two diagnoses preoperatively may not be necessary.

Treatment / Management

Individuals with an acute clinical presentation and preoperative diagnosis of focal or segmental xanthogranulomatous pyelonephritis should be treated initially with antibiotics and percutaneous drainage. Urine cultures and cultures of drained material should be performed to allow tailoring of antibiotics. Initially, broad-spectrum antibiotics are used, with third-generation cephalosporins and extended-spectrum penicillins being the most common choices. Consultation with an infectious disease specialist may be advisable.[12] Once the patient shows clinical improvement, the possibility of partial or total nephrectomy is considered.[45] If there is no clinical improvement in the patient's condition despite appropriate initial therapy, surgery should be performed.

As recurrences are rare, a partial nephrectomy is recommended if it can be safely performed with the removal of all infected tissue and calculi.[45]

Partial nephrectomy nephron-sparing surgeries should be considered when possible, especially in children.[46][47] Such cases are particularly technically challenging due to the extensive inflammation, and most patients with xanthogranulomatous pyelonephritis may not be suitable candidates. Furthermore, in the vast majority of xanthogranulomatous pyelonephritis cases, there is often little salvageable kidney function by the time of diagnosis, leading most patients to ultimately undergo a nephrectomy.[12]

In patients with diffuse or advanced-stage xanthogranulomatous pyelonephritis, the nephrectomy is the preferred treatment. Antibiotics before and after surgery help control the local infection and avoid septic complications, but antimicrobials and drainage alone are rarely sufficient therapy for xanthogranulomatous pyelonephritis. Continuing antibiotic treatment, tailored to the causative organism if possible, is recommended for at least 2 weeks post-nephrectomy.[12]

Percutaneous or internal double J stent drainage may be of limited value in patients with xanthogranulomatous pyelonephritis with nonfunctioning kidneys.

A full bowel preparation is recommended before surgery as these procedures can easily become much more complex and difficult than originally anticipated.

The goal of surgery is to remove any stones and all infected granulomatous tissue to minimize fistula formation and future recurrences. Sinuses or fistulas should be repaired if found.[6]

During kidney removal, the surgical approach should include Gerota's fascia and be equivalent to radical nephrectomy, as an associated neoplasm cannot generally be definitively excluded preoperatively.

Extensive antibiotic fluid irrigation and drain placement are recommended.

Rare cases of bilateral xanthogranulomatous pyelonephritis may need to be treated with bilateral nephrectomy and long-term dialysis, although nephron-sparing procedures may be possible in some cases, particularly in children.[47]

Laparoscopic radical nephrectomy is the procedure of choice in patients with xanthogranulomatous pyelonephritis with nonfunctioning kidneys as it is associated with less blood loss, fewer complications, reduced hospital stays, and better outcomes compared to similar open surgeries.[48][49][50][51] However, laparoscopic nephrectomy is often quite challenging in these cases due to the significant inflammation associated with xanthogranulomatous pyelonephritis.[12][52]

The conversion rate from laparoscopy to open surgery is about 30% but has been reported as high as 50%.[9][52] This conversion rate is expected to decrease as laparoscopic skills and instrumentation improve.

Laparoscopic nephrectomy can be performed in selected patients by surgeons with advanced laparoscopic skills and experience, as these are technically difficult procedures.[9][53][54][55]

The following tips and suggestions have been proposed to assist in laparoscopic radical nephrectomies performed on patients with xanthogranulomatous pyelonephritis.

• A contrast-enhanced CT scan of the abdomen should be conducted before performing surgery to assist with procedure planning.
• The placement of a percutaneous nephrostomy tube helps identify the kidney and renal pelvis. The tube also anchors the kidney in place, facilitating renal dissection.
• The placement of a ureteral catheter, especially if the patient has had prior ureteral surgery, is helpful to identify the ureter.
• Dense adhesions in patients who have had prior urological renal surgery are expected.
• Intraoperative identification of important landmarks is critical. Otherwise, an open approach should be immediately initiated.
• Dissection should be outside of Gerota's fascia.
• The upper pole dissection can be adrenal-sparing if performed through a subcapsular approach.
• The ureter should be double-clipped proximally and distally to avoid possible spillage of contaminated contents.
• If the ureter is preserved until the end of the case, it may be used as a handle.
• Freeing the superoposterior aspect of the kidney should be delayed until after the renal pedicle has been ligated.
• Consideration should be given to clamping and cutting the renal vein before the artery if dissection is challenging.
• Early ligation of the renal pedicle is suggested when possible.
• Specimen removal using a retrieval bag reduces spillage and possible contamination.
• A hand-assisted technique may be a reasonable compromise between a laparoscopic and open surgical approach in some cases.[48][50]

A small study showed that a prolonged course of preoperative antibiotics (>28 days) helped reduce inflammation and facilitate laparoscopic surgery in patients with xanthogranulomatous pyelonephritis.[56]

Having a general surgeon available is recommended as unexpected involvement of the gallbladder, liver, biliary ducts, pancreas, bowel, duodenum, spleen, or intestines may be discovered.

Vascular injury, especially on the right side, can occur easily. Dissecting the right renal hilum can be particularly challenging, especially when severely inflamed. In such cases, consideration should be given to cross-clamping, transecting, and then oversewing the hilum as a single unit or bundle.

In a large systemic review of over 1000 cases of xanthogranulomatous pyelonephritis, the following findings were found.

• Fistulas were present in 8% of patients.
• The correct preoperative diagnosis was identified only 45% of the time.
• Preoperative urine cultures were positive in only 59% of cases.
• Preoperative drainage and decompression were performed only 56% of the time.
• Laparoscopic nephrectomy was performed in just 34% of patients.
• A partial nephrectomy was performed in only 2% of cases.[49]

Differential Diagnosis

The differential diagnoses of xanthogranulomatous pyelonephritis include:

• Clear cell renal cell carcinoma
• Complex renal cyst
• Leiomyosarcoma
• Lymphoma
• Malakoplakia
• Megalocytic interstitial nephritis
• Oncocytoma
• Papillary renal cell carcinoma
• Renal abscess
• Renal angiomyolipoma
• Renal oncocytoma
• Renal neoplasm
• Renal tuberculosis
• Sarcomatoid renal cell carcinoma
• Squamous cell carcinoma of the kidney
• Wilms tumor [12][14][16][57][58][59][60][61][62]

The clinical presentation and radiographic appearance of xanthogranulomatous pyelonephritis and renal cell carcinoma are similar. However, fever and raised inflammatory markers, such as C-reactive protein and erythrocyte sedimentation rate, are most commonly associated with xanthogranulomatous pyelonephritis.

The presence of the bear paw sign is a pathognomonic feature of xanthogranulomatous pyelonephritis. In questionable or unclear cases, histological examination can confirm the diagnosis of xanthogranulomatous pyelonephritis.

Staging

Classification of Xanthogranulomatous Pyelonephritis

Xanthogranulomatous pyelonephritis is classified into focal, segmental, and diffuse forms, with the diffuse form being the most common. The diffuse form is further categorized into 3 stages according to the extent of involvement in the nearby tissues.[63]

• Focal: Involvement is localized within the cortex of the kidney, observed in about 20% of cases.
• Segmental: Involvement is limited to a regional or segmental area of the kidney.
• Diffuse: The most common presentation, characterized by widespread and diffuse renal involvement.
  • Stage 1 (Nephric): The disease is limited to the kidney. 
  • Stage 2 (Perinephric): The disease involves the renal pelvis or the perinephric fat within Gerota's fascia.
  • Stage 3 (Paranephric): The disease involves a wider area, including adjacent organs or the retroperitoneum.[46][63][64]

Prognosis

If promptly treated, the overall prognosis of xanthogranulomatous pyelonephritis is significantly improved. Unilateral cases have a much better prognosis compared to bilateral cases, which are often fatal.

Laparoscopic radical nephrectomy is the treatment of choice without any significant incidence of recurrence, but nephron-sparing surgeries may also be performed when possible. A meta-analysis reported improved outcomes with minimally invasive approaches.[51] However, due to the technical difficulties of surgical removal, the mortality rate may be as high as 7% to 10%.[15] 

A transperitoneal approach may be associated with more blood loss compared to a retroperitoneal approach, and positive urine cultures may be a poor prognostic indicator.[15]

Complications

A large multicenter study found that major complications were increased in patients with xanthogranulomatous pyelonephritis who have a quick Sepsis-related Organ Failure Assessment (qSOFA) score of 2 or higher, preoperative evidence of renal failure, perinephric extension of the disease, positive urine cultures, or enlargement of the involved kidney.[15][65]

The estimated complication rate for xanthogranulomatous pyelonephritis is about 30% to 40%.[25] The most common complications include sepsis, wall abscess, psoas abscess, and hemorrhage.[15]

Many complications of xanthogranulomatous pyelonephritis are due to the involvement of adjacent organs and may include the following:

• Cutaneous fistula formation
• Iatrogenic injury
• Infection (abscess, wound, or urinary tract)
• Nephrocolonic or pyeloduodenal fistula
• Nephrocutaneous fistula
• Perinephric abscess
• Postoperative abscess
• Psoas abscess
• Renal failure
• Secondary amyloidosis and nephrotic syndrome
• Sepsis
• Vascular injury [6][66][67]

Postoperative and Rehabilitation Care

Annual imaging of the contralateral kidney is recommended, along with aggressive treatment of urinary tract infections. 

Lower urinary tract abnormalities and voiding dysfunctions should be eliminated, if possible.

Postoperatively, patients who develop abscesses, wound infections, or cutaneous fistulas may require CT scans, percutaneous drainage, and intravenous antibiotics. 

Based on a prior history of stones or evidence of calculi in the contralateral kidney, patients at risk of nephrolithiasis should undergo 24-hour urine testing and receive appropriately focused kidney stone prophylactic treatment.[68]

Consultations

Consultations with various specialists are essential for comprehensive care in the management of xanthogranulomatous pyelonephritis. Infectious disease specialists provide expertise in antimicrobial therapy, nephrologists address renal function and electrolyte imbalances, and oncologists assist in differential diagnosis when malignancies are suspected. Pathologists confirm the diagnosis through histological examination, while radiologists aid in imaging studies for diagnosis and surgical planning. Urologists perform surgical interventions such as nephrectomy and drainage procedures, and general surgeons manage complications and intra-abdominal pathologies. This multidisciplinary approach ensures optimal treatment outcomes for patients with xanthogranulomatous pyelonephritis.

Deterrence and Patient Education

The important aspects of post-procedure care and ongoing management for patients with xanthogranulomatous pyelonephritis include:

• Antibiotics should generally be continued for at least 2 weeks post-procedure.[25]
• Annual imaging of the contralateral kidney is recommended.
• In patients with xanthogranulomatous pyelonephritis experiencing recurrent urinary tract infections, further evaluation and elimination of any correctable predisposing conditions, lesions, or obstructions are crucial. 
• Any new urinary tract infection should be aggressively treated with antibiotics.
• Patients diagnosed with nephrolithiasis should undergo 24-hour urine testing to determine appropriate kidney stone prophylactic measures.

Pearls and Other Issues

Amyloidosis and nephrotic syndrome have rarely been associated with xanthogranulomatous pyelonephritis.[69][70]

Squamous cell carcinoma has been reported in cases of xanthogranulomatous pyelonephritis.[71][72][73] These cases, while rare, have a poor prognosis, with less than 10% survival at 5 years.[71][72]

There have been a few reported cases of successfully treating localized or focal xanthogranulomatous pyelonephritis through drainage, antibiotics, and nephrolithotomy.[12][74][75][76][77][78] Such cases suggest that renal calculi are integral to the disease process and that xanthogranulomatous pyelonephritis may be reversible in some cases.[12] 

Enhancing Healthcare Team Outcomes

Xanthogranulomatous pyelonephritis is a rare and aggressive form of chronic pyelonephritis best managed with an interprofessional team approach. Due to its similar signs and symptoms, this condition is often confused with renal cell carcinoma or renal tuberculosis. Early identification and proper management of patients with xanthogranulomatous pyelonephritis are critical in reducing unnecessary morbidity and mortality. Close collaboration and communication among the healthcare professionals involved in patient care improve overall outcomes.

When left untreated, the disease can involve multiple organs. A team consisting of infectious disease specialists, oncologists, radiologists, primary care providers, pediatricians, nephrologists, pharmacists, urologists, and nursing and pharmacy staff should evaluate and treat patients with this dangerous disease.

The diagnosis of xanthogranulomatous pyelonephritis is based on evaluating the patient's clinical history and characteristic CT scan findings, such as the bear paw sign. A biopsy can be performed where histology demonstrates the characteristic lipid-laden foamy macrophages if necessary. If left untreated, xanthogranulomatous pyelonephritis can involve adjacent structures or organs and lead to fistulas. Hence, early diagnosis and treatment are essential for optimal outcomes and may help avoid the requirement of nephrectomy, thereby preserving renal function.

Immediate treatment may include antibiotics and drainage of the renal pelvis, typically percutaneously. Definitive treatment with total or partial nephrectomy typically follows and generally has a good prognosis, although surgical complications are common.

Each healthcare professional must know their responsibilities and contribute their unique expertise to the patient's care plan, fostering a multidisciplinary approach. Effective interprofessional communication is paramount, allowing seamless information exchange and collaborative decision-making among the team members.

Care coordination plays a pivotal role in ensuring that the patient's journey from diagnosis to treatment and follow-up is well-managed, minimizing errors and enhancing patient safety. By embracing these principles of combining skills, strategy, ethics, shared responsibilities, interprofessional communication, and care coordination, healthcare professionals can deliver optimal patient-centered care, ultimately improving outcomes and enhancing team performance in the management of xanthogranulomatous pyelonephritis.