Title : XanthoGranulomatous (XGP) Pyelonephritis mimicking locally advanced renal cell carcinoma
Abstract:
Introduction: Xanthogranulomatous pyelonephritis (XGP) is an uncommon inflammatory renal condition associated with urinary obstruction, infection and calculi. Focal XGP may resemble renal cell carcinoma (RCC), particularly when typical radiological features are absent. We report a case in which XGP presented as an enhancing renal mass with renal vein thrombosis and paracaval lymphadenopathy.
Case Presentation: A 75 year-old patient presented with right flank pain, fever and vomiting. Investigations demonstrated leukocytosis, renal impairment and right hydronephrosis secondary to an upper ureteric calculus. The collecting system was initially decompressed by percutaneous nephrostomy, followed by percutaneous nephrolithotomy. After improvement in renal function, contrast-enhanced CT demonstrated a 49 × 35 × 43 mm right renal mass. The lesion enhanced from 33 HU to 118 HU and contained non-enhancing areas. Renal vein thrombosis and multiple paracaval lymph nodes were also present. The imaging findings were considered suspicious for RCC, with a radiological stage of T3aN2M0. The patient underwent laparoscopic radical nephrectomy. Histopathology demonstrated renal parenchyma extensively infiltrated by foamy macrophages and inflammatory cells, consistent with XGP. No malignancy was identified. Postoperative recovery was uncomplicated.
Discussion: The combination of a strongly enhancing renal mass, renal vein thrombosis and regional lymphadenopathy favoured RCC on preoperative imaging. However, the preceding obstructing calculus, hydronephrosis and infection were also compatible with XGP. This case demonstrates the difficulty of distinguishing focal XGP from renal malignancy when the usual CT appearance is absent. The distinction has practical implications. When imaging cannot exclude malignancy, nephrectomy may be required both for definitive treatment and diagnosis. Histopathological examination remains decisive in such cases.
Conclusion: Focal XGP can closely resemble locally advanced RCC. In a renal mass occurring alongside calculi, obstruction or infection, XGP should remain in the differential diagnosis even when CT demonstrates marked enhancement, venous thrombosis or regional lymphadenopathy. Keywords: xanthogranulomatous pyelonephritis; renal cell carcinoma; renal mass; renal vein thrombosis; nephrectomy.
