Xanthogranulomatous Pyelonephritis A Review and Update of the Literature
Xanthogranulomatous pyelonephritis (XGP) is a rare chronic destructive granulomatous inflammatory process that affects sporadically the parenchyma of the kidney and the disease tends to be associated in many cases with long-term urinary tract obstruction, urinary tract infection and also in cases with calculi within the kidney. XGP does affect females more commonly in comparison with males, it does affect all age groups including newly born up to the elderly. Majority of the patients tend to be symptomatic and some of the symptoms could include: pyrexia, flank / loin / abdominal pain, palpable mass in loin/abdomen/costovertebral region, weight loss, visible haematuria. There may be associated diabetes mellitus, obesity, or immune deficiency. There may be anaemia and leucocytosis upon blood tests. Urine cultures may grow Escherichia coli, or proteus but in other situations the urine culture could be negative. Ultrasound scan of renal tract, CT and MRI scan of abdomen and pelvis tend to be undertaken in the assessments of patients. CT scan has globally been the establishment of radiology imaging diagnosis. Radiology imaging may demonstrate focal or diffuse XGP but the diffuse form is more common. It may reveal multiple low-attenuated cystic masses in the kidney, calculi in the kidney, hydronephrosis / dilated calyces / bear’s paw appearance in some cases. Macroscopy examination of the specimen of the kidney would tend to show multiple yellow nodules around calyces, and the lesion may form a mass or be infiltrative. Pathology examination of specimens of XGP would tend to show granulomatous inflammatory infiltrate that consists of neutrophils, lymphocytes, plasma cells, xanthomatous histiocytes, as well as multi-nucleated giant cells. Immunohistochemistry staining may show positive staining for CD68. Some of the differential diagnoses include: clear cell carcinoma of the kidney, papillary renal cell carcinoma, sarcomatoid renal cell carcinoma, leiomyosarcoma, malakoplakia of kidney, megalocystic interstitial nephritis, and renal replacement lipomatosis. Majority of diffuse cases have been treated by nephrectomy and antibiotics and some focal cases have been treated by partial nephrectomy and antibiotics but on very rare occasions cases have been treated by drainage of the abscess with biopsy and in conjunction with antibiotics. Percutaneous nephrostomy has also been undertaken pre-operatively to decompress the kidney by draining the abscess in the occasional case.