XGP is an uncommon chronic inflammation of renal parenchyma, firstly described in 1916 [8]. XGP occurs approximately 1% of pyelonephritis in adults and 16% of pediatric nephrectomy specimens [9, 10]. Recently, Stoica I and colleagues retrospectively reviewed XGP cases from 1963 to 2016. Sixty-three patients (95.5%) underwent nephrectomy and 3 patients (4.5%) underwent partial nephrectomy [4]. XGP is frequently unilateral and bilateral cases of XGP are extremely rare. Shah K and colleagues reported one bilateral XGP child case managed non-surgically [11]. Hyla-Klekot L and colleagues reported one bilateral XGP patient managed by intensive therapy and partial nephrectomy [12].
The exact etiology of XGP is unclear and most of common associated factors are long term urinary tract obstruction or infection. Renal calculi, frequently staghorn stones, may be seen in up to 100% of the published cases [6]. Altered immune response and intrinsic disturbance of leukocyte function are other possible factors [1, 5, 10].
CT scan is priority for preoperative evaluation of XGP. Based on CT findings, XGP can be divided into diffuse type (92%) or focal type (8%) [13, 14]. Typical CT features of diffuse XGP patients are destruction of renal parenchyma and replacement by multiple, low-attenuation lesions with strong enhancement, described as “bear paw sign”. Depending on the extension of inflammation, XGP can be classified as three stages: nephric XGP (stage I), perinephric XGP (stage II) and paranephric XGP (stage III). In focal XGP patients, CT frequently reveal a well-defined localized intra renal lesion with hypo-attenuation [15].
The management of XGP is different for diffuse versus focal. Nephrectomy is the standard treatment approach for diffuse XGP patients, while medical therapy with antibiotics or nephron sparring surgery is priority for focal XGP patients. In the study of Korkes F et al., all 41 cases of XGP underwent nephrectomy [6]. In the study of Çaliskan S et al., one patient underwent partial nephrectomy and 12 patients were performed nephrectomy in all 13 cases of XGP [5].
In the study of Korkes F et al, 41 cases of XGP were retrospectively reviewed and all patients were symptomatic [6]. In the study of Chlif et al., 12 pseudotumoural XGP cases were reviewed [13]. An obstructive renal stone was shown in nine patients and one patient presented with loin pain. Blood investigations showed higher C-reactive protein in one patient and gram-negative organisms in four patients. In our study, the present case did not have any abnormal clinical symptoms and/or signs. Routine laboratory tests were normal. CT and IVP revealed renal cancer rather than XGP. Atypical clinical and radiologic characteristics make the preoperatively correct diagnosis difficult. In order to avoid misdiagnosis and mistreatment, preoperative renal mass biopsy is priority, although the inevitable false negative results were objectively existed [16]. Fitouri Z reported a XGP case which was confirmed by percutaneous renal lesion biopsy. The patient was successfully treated with 8 weeks’ antibiotic therapy [17]. Ho CI et al. also reported a XGP patient diagnosed by renal mass biopsy, who recovered by antibiotic therapy for 2 months [18]. Renal tumor biopsy can be used for treatment decision making, especially when a mass is suspected to be infectious, hematologic or metastatic [19, 20]. However, the indications of preoperative needle biopsy are still unclear and vary among centers.
In summary, we reported a case of focal XGP without typical clinical and radiological characteristics, which can mimic infiltrative renal cancer. In special cases, preoperative renal mass biopsy could be performed to avoid misdiagnosis and mistreatment.
