Xanthogranulomatous Pyelonephritis--the "Great Imitator" Justifies Its Name

Abstract

A case of focal xanthogranulomatous pyelonephritis (XGP) clearly imitating renal tumour is presented. The authors underline the need to include focal XGP in the preoperative differential diagnosis of a renal mass even in the absence of typical characteristics.

Ultrasonographic Features of Focal Xanthogranulomatous Pyelonephritis

“…The disease is usually unilateral, [1][2][3][4][5][6][7][8][9][10][11][12][13][14] as in all our cases. Two forms of XGP have been described: a focal (localized, segmental, tumefactive) form (15%) and a diffuse form (85%).…”

“…[1][2][3][4][5][6]10,12 In the diffuse form, generalized renal enlargement with multiple hypoechoic areas representing calyceal or pelvocalyceal dilatation and parenchymal destruction, hyperechoic foci with clean posterior acoustic shadowing representing renal calculi or a staghorn stone, and debris in hydronephrosis may be seen. The infrequent focal form of XGP confined to 1 part or pole of the kidney, usually occurring in women and children, may not present findings similar to those of the diffuse form.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12] Other suggested interrelated etiologic features are infection, ineffectively treated urosepsis, chronic renal ischemia causing localized alterations in renal metabolism, lymphatic obstruction, alterations in lipid metabolism, altered immune response, malnutrition, and congenital urinary anomalies, most commonly a duplex kidney. 3,12 In addition to the most common symptoms of flank pain and fever, other symptoms such as fatigue, weight loss, dysuria, and a tender flank mass may be present, with laboratory data of leukocytosis, anemia, and an increased ESR.…”

“…[1][2][3][4][5]12 Imaging findings of focal XGP may imitate those of neoplastic diseases (such as RCC, lymphoma, or leukemia in adults and Wilms tumor, congenital mesoblastic nephroma, or a multilocular cyst of the kidney in children) and other focal inflammatory renal parenchymal diseases (such as actinomycosis, renal tuberculosis, renal abscess, and malakoplakia); consequently, focal XGP is often misdiag- nosed preoperatively. [1][2][3][4][5][6]10,12,13 The preoperative clinical and radiologic diagnosis based on ultrasonography and CT, compared with the final pathologic diagnosis, was incorrect in all cases in our study: RCC (n = 11), Wilms tumor (n = 2), and renal abscess (n = 2).…”

Rare Coexistence of Keratinizing Squamous Metaplasia with Xanthogranulomatous Pyelonephritis

“…2,3 A preoperative clinical and radiologic diagnosis of XPN is difficult due to its striking similarity to renal cell carcinoma (RCC). 4 Definitive diagnosis is usually made following nephrectomy. 2,6 The role of fine needle aspiration cytology (FNAC) has been limited in the past due to the great resemblance between the cells of XPN and those of RCC.…”