Aspiration cytology of focal xanthogranulomatous pyelonephritis: A diagnostic challenge

Xanthogranulomatous pyelonephritis

Xanthogranulomatous pyelonephritis is an uncommon chronic destructive granulomatous process of renal parenchyma in association with long-term urinary tract obstruction and infection. It affects females more often than males, with a wide range of age, from newborn to elderly. Almost all patients are symptomatic and the most common symptoms are flank or abdominal pain, lower urinary tract symptoms, fever, palpable mass, gross hematuria, and weight loss. The common laboratory findings are leukocytosis and anemia. Urine cultures most often reveal Escherichia coli and Proteus mirabilis . Computed tomography is the mainstay of diagnostic imaging for xanthogranulomatous pyelonephritis. Imaging studies may demonstrate diffuse or focal form. Histologically, xanthogranulomatous pyelonephritis presents a granulomatous inflammatory infiltrate composed of neutrophils, lymphocytes, plasma cells, xanthomatous histiocytes, and multinucleated giant cells. The differential diagnosis includes clear cell renal cell carcinoma, papillary renal cell carcinoma, sarcomatoid renal cell carcinoma, leiomyosarcoma, malakoplakia, and megalocytic interstitial nephritis. Both antibiotics and surgery can be treatment options depending on the patient's disease status.

[Imaging features of xanthogranulomatous pyelonephritis]

Pseudotumoral xanthogranulomatous pyelonephritis is a rare chronic renal infection. Preoperative diagnosis is difficult because of its non-specific presentation. The purpose of this retrospective review of 8 cases is to assess the value of different imaging techniques in the evaluation of this pathology. Six males and 2 females, aged 29 to 75 years were included. The right kidney was involved in 5 cases and the left kidney was involved in 3 cases. Involvement was upper polar in 2 cases and lower polar in 6 cases. A kidney stone was present in 3 cases. US showed a heterogeneous hypoechoic lesion in 3 cases, a homogeneous hypoechoic lesion in 3 cases, and isoechoic lesion in 1 case and a cystic lesion in 1 case. CT showed a focal solid lesion with peripheral enhancement in 4 cases and a cystic mass with peripheral enhancement in 3 cases. US features are non-specific. CT shows a non-specific renal mass, the presence of obstruction and demonstrates perirenal involvement. Preoperative MRI, not performed in our patient population, demonstrates specific changes in the perirenal fat that suggests the diagnosis. The diagnosis of pseudotumoral xanthogranulomatous pyelonephritis can be suspected on a constellation of clinical and laboratory findings combined with non-specific features on CT and US and specific MRI features of perirenal fat changes. Percutaneous biopsy may be needed in selected cases to confirm diagnosis.

An unusual case of xanthogranulomatous pyelonephritis in an immunosuppressed patient with systemic lupus erythematosus

Xanthogranulomatous pyelonephritis (XGP) is invariably associated with urinary tract obstruction, infection and nephrolithiasis. We report an unusual case of XGP occurring in an immunosuppressed patient in the absence of either urinary obstruction or nephrolithiasis, presenting as a diagnostic dilemma, and highlighting the possible role of glucocorticoid immunosuppression towards its pathogenesis.