[Xanthogranulonatous pyelonephritis: report of 5 cases]

Xanthogranulomatous pyelonephritis (XGP) is an unusual form of chronic pyelonephritis in which the renal parenchyma is destroyed and replaced by lipid-laden foamy macrophages. It usually affects middle-aged women with a history of recurrent urinary tract infection, diabetes, or kidney stones. The inflammatory process is usually diffuse and can extend beyond the kidney. The rare focal forms may simulate primary renal tumours. The preoperative imaging diagnosis may be difficult. We reported five cases of XGP, The findings of ours were recorded including kidney size, shape, contour, the echogenecity of the renal parenchyma, the internal echoes of the dilate collecting system, the presence of perinephric fluid accumulation and obstruction. One of the 5 cases was a male patient, and the other four were female, with a mean age of 53 years. He affected kidneys of the 5 cases swelled in different degrees, and one of them was found with line-like anechoic fluid. Among the 5 cases, one kidney appeared as diffusely reducing of the parenchyma echogenicity, multiple hypoechoic areas, disappearance of corticomedullary differentiation and multiple hyperecho with shadow. A round cystic anechoic lesion was found in one kidney, with internal punctate echo and peripheral fluid. Ultrasonographic finding of 1 case was extremely hypoechoic lesion on the left kidney, protruding from the outline of the kidney, with the partial renal capsule discontinuous, the less clear boundary, and a little blood flow in it. Ultrasonographic demonstration of 2 cases was mild dilatation of the collecting system with irregular wall thickening and internal hypoechogenicity, and 1 case was solid lesion with less clear boundary to the pelvic wall and a small amount of blood flow signal, the another 1 case was showed floccule without internal blood flow. Three cases were caused by chronic obstruction verified by operation, of which one was staghorn calculi, one was poorly differentiated squamous cell carcinoma in the middle part of the ureter, and one was inflammatory stricture of upper ureteral. Through analysis of the above five cases and review of related literature, we explored diagnoses and management of the patients with XGP. Xanthogranulomatous pyelonephritis (XGP) is a rare chronic variant of pyelonephritis characterized by destruction of the renal parenchyma. Combining ultrasonographic features of XGP with clinical recurrent urinary infection and chronic obstruction, XGP can be included in the differentiation. The diagnosis of XGP suspected by ultrasound can be clarified by CT, MRI, contrast-enhanced ultrasound.