Xanthogranulomatous pyelonephritis--study of 14 cases.
Xanthogranulomatous pyelonephritic (XPN) is a histologically well defined entity. It may mimic renal cell carcinoma or inflammatory diseases like tuberculosis. There are a few series reported in the Western as well as Indian literature.,,,,, We came across 14 cases of XPN during a five year period. These cases have been reviewed and reported here.
Out of 85 surgically resected nephrectomy specimens for non-tumourous conditions, 13 showed the changes of xanthogranulomatous pyelonephritis (X.P.N.), over a five year period from 1979-1985. During the same period one more case was diagnosed at autopsy. These 14 case; were studied retrospectively to find out clinical and morphological features and probable histogenesis.
The age-range of all 14 cases was between 20 and 60 years, the majority being around 40 years. The chief presenting complaint was pain in the flank (12 out of 14 cases) with a palpable lump in 7 over a period of 6 months to 1 year prior to surgical resection. One patient presented with hypertension, one with haematuria and one with the picture of chronic renal failure. All 13 surgical cases had non-functioning kidneys on IVP and the autopsy case was not investigated.
The morphological features of the kidney varied from small contracted kidneys to very large pyonephrotic kidneys. The calculi were seen in all of them and were either oxalate or mixed type containing a mixture of triple phosphate either pure or with calcium oxalate. The proteus group of organisms were isolated from seven cases.
On staging, seven cases showed nephric stage (Stage 1). There were classical yellowish nodules seen scattered around pelvic mucosa and the renal parenchyma was reduced to glistening white fibrous tissue. Three cases showed perinephric abscesses with extension of yellowish nodules in the perinephric tissue (Stage 11) producing haemorrhages [Fig. 1]. Two cases (No. 11, 12) showed stage III peranephric type of lesions. In addition to renal and parirenal involvement, the entire ureters were thickened. The lumina were obliterated with ulceration at places. During operations there were dense adhesions and difficulty in performing nephre-ureterectomy. The second case of stage III was diagnosed at autopsy. The remaining two cases (cases No. 13, 14) had focal involvement, one of which had tuberculous pyonephrosis of the remaining segments.
Histology showed presence of granulomas distributed along the pelvic mucosa consisting of a mixture of foamy histiocytes with giant cells, neutrophils and plasma cells. The granulation tissue was seen around the granulomas. Among the granulomas, areas of supportive necrosis with neutrophilic exudate was seen. The renal parenchyma was replaced by hyalinised connective tissue. Very few glomeruli which were preserved also showed evidence of periglomerular fibrosis. Intestitial fibrosis and collection. of lymphoid follicles were seen away from the pelvic mucosa. In cases no. 2 and 4, the - arterioles showed intimal hyaline thickening with reduplication of internal elastic lamina as an evidence of hypertension. In case no. 14, there were classical caseating tuberculous granulomas affecting a part of the kidney. The acid fact stain for tubercle bacilli was positive [Fig. 2].
The age range in our series was 20 to 65 years, a finding similar to that observed by others.,,, However, a few cases of X.P.N. have been reported in children. Male to female ratio was 4:3 in the present series; however, a definite female predominence was reported in the Western series.,,
The usual presentation of a lump in the renal region could be correlated with the large-sized kidneys, parirenal adhesions and capsular involvement as seen in the perinephric stage. In three cases (No. 3, 4, 5), the kidneys were small weighing between 50 and 80 gm, and pain was the only symptom in these cases. One of them presented with long standing hypertension. In these patients, xanthogranulomatous pyelonephritis could not be suspected clinically.
Focal X.P.N. was seen in two of our cases? However, the entity was found to be common in children.
In one of our patients, tuberculous pyelonephritis was also present. Since tuberculosis still remains endemic in Inlia, renal tuberculosis is not an indistinct entity and its association with X.P.N. has no special significance.
Calculi and proteus infection were common associated findings which had been reported by many workers.,,,,
In one case (No. 11), urothelium showed the presence of squamous metaplasia. As metaplasias are known to occur in association with calculi,, its presence along with X.P.N. is not surprising. However, only isolated incidence of such lesions are on record, where the metaplasia had already developed into squamous cell carcinoma.
Urinary tract infection played an important role in producing chronic pyelonephritis as confirmed by gross and histological features leading to an end stage kidney in all cases of X.P.N. studied. Moreover, calculi rich in phosphates were shown to harbour the infecting micro-organisms. The end stage kidney due to ischaemic stage becomes a site of immunologically suppressed organ. The obstructive lesion also can have an added effect. In such an organ, the repeatedly infecting micro-organisms could not be phagocytosed by neutrophils; this stimulates the proliferation of histiocytes. Experimentally in rats, it was shown that histiocytes could be produced by resorption of retained pus following ureteral obstruction.
Electron microscopy has shown that X.P.N., megalocytic interstitial nephritis and malakoplakia are related conditions, characterised by histiocytic proliferation, bearing the end products of phagocytosed bacteria.
Thus, X.P.N. appears to be produced in an end stage kidney which is facing repeated showers of micro organisms belonging mostly to coliform group.
We are thankful to Dr. N. A. Dabholkar, Dean of L. T. M. M. College & L. T. M. G. Hospital, Sion, Bombay-22, for allowing us to publish this article.