Xanthogranulomatous pyelonephritis (report of 2 cases).
Xanthogranulomatous pyelonephritis is a rare type of pyelonephritis and poses diagnostic difficulties on clinical as well as histological grounds. It has been reported in the literature under different designations vie. staphylomycosis, foam cell granuloma, pyelonephritis xanthomatosa, renal xanthomatosis, chronic pyelonephritis with xanthomatous change, tumefactive xanthomatous pyelonephritis and simply xanthogranulomatous pyelonephritis. It was first described by Schlagenhaufter, who reported 5 cases and called it staphylomycosis.
Since no specific clinical picture exists and histologically it closely mimics clear cell carcinoma, an accurate account of its actual pathology, diagnosis and report of 2 cases is discussed here.
A 64 year old Hindu male was complaining of a gradually increasing swelling in the right lumbar region. The patient noticed this swelling 1½ years back which was about the size of an egg and painless, not associated with fever, burning micturition, haematuria, pyuria etc. The swelling went on increasing throughout this period attaining the present size. For the last 1 month, the patient was complaining of red coloured urine off and on, blood being mixed with urine, painless and no passage of clots.
On examination, the patient was of average build, anaemic but not jaundiced; no lymph nodes were palpable. Local examination revealed a normally shaped abdomen with fullness in the right flank. A firm to hard mass was palpable in the right lumbar region; it was irregular, nodular, with ill-defined margins, fixed, bimanually palpable and non-tender. Opposite silo kidney was not palpable. There was no free fluid in the abdomen. P-R examination was non-contributory.
The haemoglobin was 7.8 gm%; ESR was 60 mm/1st hour (Westergren method). Albumin and sugar were absent in the urine but 10-15 pus cells and 4-6 RBCs/HPF were detected in urine. Blood urea was 32 mg%, blood sugar was 88 mg% and the serum creatinine was 1.0 mg%. X-ray flat plate of the abdomen showed a soft tissue mass in the right lumbar region but no radio-opaque shadow. IVP showed a nonfunctioning right kidney and a normally functioning left kidney.
With a provisional diagnosis of hypernephroma, right nephrectomy was done.
The kidney specimen measured 11 cm x 6.5 cm x 5 cm in size with a thickened and adherent capsule all-through. The capsule did not strip off easily at most places. Cut surface revealed loss of differentiation between the cortex and the medulla which showed peripheral irregular cystic spaces (dilated calices) along with large irregular diffuse yellowish areas at the upper pole and the pelvis. There were no impacted stones.
The renal parenchyma, in general, showed changes of advanced chronic pyelonephritis with glomeruli showing changes of atrophy, hyalinized sclerosed glomeruli and periglomerular fibrosis. The stroma showed massive infiltration by round cells, polymorphs and a few eosinophils. Accompanying the dense fibrocollagenous stroma were the diffuse masses of large uniform lipid laden foam cells (xanthoma cells) with small uniform nuclei and scattered strands of collagenous bundles separating them At places there were giant cells suggestive of Touton giant cell type morphology. PAS reaction showed presence of diastase resistant, PAS-positive granularity within the foam cells; lipid stain revealed lipids in the foam cells [Fig. 1].
A 42 year old Hindu male had right upper quadrant flank pain for the last one year associated with irregular, low grade fever without chills and rigor, There was no history of haematuria or pyuria. Physical examination revealed an averagely built anaemic male with a few discrete, palpable lymph nodes in the axilla
Abdominal examination revealed fullness with a bimanually palpable, fixed, tender, smooth surfaced mass in the right lumbar region. Hemoglobin was 9.0 gm%, TLC was 7,600 per cmm with P-60% and L-40%. ESR was 48 mm in the first hour. Urine examination showed plenty of pus cells with occasional RBCs. It was sterile for pyogenic organisms with acidic pH. Blood urea was 40 mg% and serum creatinine was 1.2 mg%.
Plain skiagram of the abdomen depicted a soft tissue mass in the right lumbar region without calcilfication. X-ray of the chest was noncontributory but IVP revealed a non functioning right kidney.
With a provisional diagnosis of tubercular pyelonephritis, a nephrectomy was done. The kidney was about 15 cm x 10 cm x 6 cm in size with adhesions all around and had irregular nodular surfaces and patchy yellowish areas at some places [Fig. 2]. The cortex and medulla could not be differentiated. Microscopically, there were changes of chronic pyelonephritis with infiltration of cells; the reticulin stain showed reticulin fibres outlining the groups of foam cells. Lipid staining revealed lipids in foam cells.
Xanthogranulomatous pyelonephritis is a rare type of pyelonephritis. Schlagenhaufter, in 1916, first reported it as a distinct histological entity but called it as staphylomycosis because it contained staphylococci with foam cells, leucocytes and fibroblasts. Since then, many different terms have been put forward to denote the same histological features but xanthogranulomatous pyelonephritis is preferable, since it is descriptive of the histopathology of the process which is characterized by a segmental- or diffuse replacement of renal paranchyma, already damaged by chronic pyelonephritis by lipid containing macrophages and occasionally giant cells within areas of granulomatous reaction.
Putschar, in 1934, provided true description of another variant of pyelonephritis in the form of xanthogranulomatous pyelonephritis, when he described small abscesses surrounded by large collection of foam cells resembling butter.
In 1957, Selzer et al first described the similarity of xanthogranulomatous pyelonephritis to renal cell carcinoma. It is stressed so because the authors had an opportunity to see a case, 9 years after surgical and pathological confirmation of the presence of an inoperable hypernephroma without any X-ray therapy or chemotherapy. Microscopic sections of removed tumour showed the presence of lipophages now characteristics of xanthogranulomatous pyelonephritis resembling clear cell carcinoma.
Similarly, Anhalt et al have quoted a patient who underwent nephrectomy for renal lump; the biopsy was initially clear-cell-carcinoma but after reading an article on it, it was again reviewed and was found to be xanthogranulomatous pyelonephritis. The exact etiology of the condition is not known but various theories have been put forward by various authors. According to Anhalt et al, one theory states that bacterial infection leads to tissue destruction and subsequent liberation of lipids calling forth the histiocytic response. Second view is of metabolic defect with a secondary inflammatory reaction. Third theory reveals a combination of the above two views plus other factors such as vascular insufficiency and ureteral or pelvic obstruction from stricture or calculus.
Barrie advanced the idea that the kidney is like brain in that any degenerative process may show accumulation of lipids. Suppuration is a common factor and it is caused by or associated with calculi. Farrow et al reported that renal lipomatosis and xanthogranulomatous pyelonephritis seem to be similar disease entities since they are both associated with obstruction, infection and stone diseases in most cases; one main differential point is whether foam cells and macrophages are present or not.
Proteus organisms seem to predominate; experimentally it has been reproduced in rabbits with elevated lipids.
The clinical picture is consistent with that of hypernephroma as the patient with that disease may have local pain, a swelling and haematuria. In this series also, both patients had noted gradually increasing swelling and one patient had painless haematuria. Elevation of temperature with or without chills and rigor may be a feature as in one of our present cases. IVP may not differentiate between inflammatory and neoplastic disease, as renal architecture is distorted in both.
From the standpoint of gross pathology, a large, yellow, tumefactive mass replaces a portion of the kidney and may extend into the perinephric tissue. Farrow et al had suggested that diagnostically, it should be suspected when signs and symptoms of perinephric abscess are present and on exploration a large, yellow, tumefactive mass is found.
Microscopically, one is stuck with a number of clear foamy cells, arranged in sheets and cords, associated with large numbers of lymphocytes and plasma cells of inflammatory reaction; at first glance, the picture is similar to hypernephroma; however, a close study fails to reveal any papillary or acinar arrangements of cells. Furthermore, nuclei are uniform in size, shape and stainability and resemble those of histiocytoma.
Saeed et al differentiated the features of xanthogranulomatous pyelonephritis, renal clear cell carcinoma and malacoplakia and histiocytoma in a tabular form.
Summarising these, the author had stated that the extent of involvement is diffuse, and non-encapsulated with varying amount of fibrosis in xanthogranulomatous pyelonephritis whereas it is a well demonstrated and unipolar mass in renal cell carcinoma. Retroperitoneal involvement, venous invasion, metastasis and increased vascularity are uncommon in the former whereas they are all found in renal cell carcinoma.