Xanthogranulomatous pyelonephritis is a rare chronic obstructive pyelonephritis characterized by infiltration of the renal parenchyma with lipid laden Macrophages and an enlarged non-functional kidney [4]. It is most commonly associated with superinfections by bacteria such as E.coli, Proteus mirabilis, and occasionally Pseudomonas species [5]. Renal calculi, diabetes mellitus and immunosuppressive conditions are also reported to predispose an individual to this rare renal tumor [6]. The affected kidney is usually non-functional and can be mistaken with common renal neoplasms because it may locally extend to invade adjacent structures such as the psoas muscle, pancreas, spleen and the duodenum.
In most cases, Xanthogranulomatous pyelonephritis involve one kidney but cases of bilateral renal involvement have been published [7, 8]. XGP is predominantly a disease of adults reported to occur in approximately 1 % of pyelonephritis. It is four times more common in females than males with a peak age at fifth and sixth decades of life [9]. XGP in adults affects both kidneys equally but it involves the left kidney more often than the right kidney in children as it was the case for our patient [10]. XGP in children occur more in boys usually from 8 years of age and it is encountered in approximately 16 % of pediatric nephrectomy specimens [11]. Histologically the disease is characterized by renal parenchyma infiltration by lipid laden macrophages and chronic inflammatory cells in line with the histological finding for our patient [12]. The exact mechanism of xanthogranulomatous pyelonephritis (XGP) is unclear, but it is generally agreed that the disease process requires a long-term renal obstruction superimposed with infection by Proteus species, Escherichia coli and Pseudomonas species in a setting of impaired ability of the body to clear the infection. Congenital urinary tract malformations are highly linked with development of XGP in children [13]. Ultrasound and other imaging modalities can be used to suspect XGP, but CT-scan and MRI are thought to be more sensitive and usually show an enlarged nonfunctional kidney with or without invasion to neighbouring structures [14].
On abdominal CT scan, our patient showed foci of calcifications with no calculi but renal calculi (frequently of staghorn proportions) are reported in up to 80 % of cases with XGP.
XGP can manifest with malignant features capable of local tissue invasion and destruction explaining the frequent confusion with renal neoplasm hence it is often referred to as a pseudo tumor [15].
Our case presented with one year history of antibiotic refractory urinary tract symptoms and fever, which is a typical presentation of this condition [16]. The obstruction associated with XGP in the pediatric population is frequently linked to congenital urinary tract malformations than from obstructive calculi but our patient did not have any anomaly or calculi from the imaging performed. Histologically; XGL has a pathognomonic appearance characterized by lipid laden foamy macrophages in a mixture of acute and chronic inflammatory cells [17]. Other laboratory investigations including complete blood count and differential are usually nonspecific but may show leukocytosis and anemia with elevated erythrocyte sedimentation rate.
If XGP is unilateral, serum creatinine and urea are usually normal, except for cases of bilateral extensive disease destroying both kidneys in which case long-term renal replacement therapy is required. Urine analysis reveals leukocytosis, proteins and culture may be positive for bacteria which also helps to ascertain the antibiotic sensitivity pattern [18].
Surgery remains the mainstay for a definitive diagnosis and cure of Xanthogranulomatous pyelonephritis (XGP) requiring extirpation (nephrectomy) as the standard surgical technique but for small tumor, partial nephrectomy can be attempted. In most cases extirpation is necessary because the disease results in an infected, nonfunctioning kidney. Nephron-sparing surgery is an option, especially in cases of bilateral disease with demonstrated significant residual functional renal tissues [19]. Laparoscopic nephrectomy is feasible for some cases of XGP and few cases have been cured by this operative modality and its advantage over radical nephrectomy is being explored. Some pediatric case series of laparascopic resection of XGP have reported promising success with this apporach [20]. The technical difficulty and complications of the procedure raise concern on its wide spread use especially in limited resource settings [21].
Medical therapy with antibitics only has been effective for treatment of XGP in a handful of cases but may be appropriate as a temporary measure for patients requiring workup before nephrectomy and prophylactic antibiotics should be administered before and after surgical intervention. The choice of antibiotic has to be tailored toward the identity and sensitivity of the offending organism. Proteus species and E coli are usually sensitive to several antibiotics, including first-generation cephalosporins which can be started empirically pending sensitivity results [22]. Pseudomonas species has a narrow spectrum of sensitivity and usually require the use of aminoglycosides, third-generation cephalosporins, or fluoroquinolones. For non-septic patients and those evaluated on an outpatient basis, some authors recommend use of oral antibiotics until surgery, at which point intravenous antibiotics should be administered [23]. There is no clear recommendation regarding the duration of antibiotic therapy but data from published case series favor a continuation of oral antibiotics at least for one week post nephrectomy [24, 25]. Our patient underwent left radical nephrectomy and was kept on intravenous Piperacillin-tazobactam for 7 days post nephrectomy and remains asymptomatic at the time of submission of this manuscript.
