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CASE REPORT Table of Contents   
Year : 2009  |  Volume : 52  |  Issue : 4  |  Page : 552-553
Idiopathic renal replacement lipomatosis: A case report and review of literature


1 Department of Pathology, Topiwala National Medical College and BYL Nair Charitable Hospital, Mumbai Central- 8, India
2 Department of Urology, Topiwala National Medical College and BYL Nair Charitable Hospital, Mumbai Central- 8, India

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Date of Web Publication1-Oct-2009
 

   Abstract 

Idiopathic renal replacement lipomatosis is a rare condition in which the renal parenchyma, especially the renal sinus is replaced with adipose tissue with increase in perirenal fat. We report a case of renal replacement lipomatosis presenting as a renal mass clinically. The computed tomography scan revealed low density and nodular masses of adipose tissue within the renal parenchyma. The differential diagnosis before surgery was angiomyolipoma, lipoma, and xanthogranulomatous pyelonephritis. After the histological examination and extensive literature search, the diagnosis of renal replacement lipomatosis was made. It is a rare entity and may be missed if not considered due to lack of experience, so we hope that more urologists, radiologists, and pathologists become aware of this entity and recognize it.

Keywords: Idiopathic, renal replacement lipomatosis

How to cite this article:
Shah VB, Rupani AB, Deokar MS, Pathak HR. Idiopathic renal replacement lipomatosis: A case report and review of literature. Indian J Pathol Microbiol 2009;52:552-3

How to cite this URL:
Shah VB, Rupani AB, Deokar MS, Pathak HR. Idiopathic renal replacement lipomatosis: A case report and review of literature. Indian J Pathol Microbiol [serial online] 2009 [cited 2019 Aug 21];52:552-3. Available from: http://www.ijpmonline.org/text.asp?2009/52/4/552/56163



   Introduction Top


Idiopathic renal replacement lipomatosis (RRL) is a rare, benign condition in which the renal parenchyma, especially the renal sinus, hilum, and perirenal spaces are replaced with mature adipose tissue. [1],[2],[3] We report our experience with one such case along with review of literature.


   Case Report Top


A 43-year-old male was admitted to our hospital with complaint of flank pain which was continuous and dull aching. There were no other significant complaints. On physical examination, there was a non-tender, firm, ill-defined mass in the left lumbar region. Investigations revealed mildly elevated blood urea nitrogen and serum creatinine. Computed tomography (CT) scan revealed low density and nodular masses of adipose tissue with hydronephrosis of left kidney and abnormal excessive peripheral fat. A diagnosis of lipomatous neoplasm like lipoma or angiomyolipoma or focal xanthogranulomatous pyelonephritis was made. The other kidney was normal. Left nephrectomy was performed. Specimen received was measuring 18Χ13Χ8 cms with intact Gerota's fascia. On cut surface, the entire parenchyma was replaced with adipose tissue with extremely atrophied renal parenchyma and moderately dilated pelvicalyceal system [Figure 1]. Microscopic examination showed extensive fatty infiltration in the renal parenchyma with atrophied renal parenchyma at periphery with sclerosed glomeruli, thyroidisation of tubules, interstitial fibrosis, and thickened blood vessels. There were areas of demarcation between the adipose tissue and renal parenchyma as well as infiltration by adipose tissue [Figure 2]. Inflammation was moderate and comprising of lymphocytes, polymorphs and few macrophages. Pelvicalyceal lining was unremarkable. No xanthomatous change or any neoplasm was noted. A diagnosis of renal replacement lipomatosis was made after thorough literature search and confirming that the case fitted well with other cases of this entity described in the literature. After one year of follow-up, the patient is asymptomatic.


   Discussion Top


Kutzmann was amongst the first ones to describe this unusual entity in 1931 as reported by Peacock and Balle. [4] Renal sinus lipomatosis, replacement lipomatosis, and fibrolipomatosis of kidney are the terms used for this rare condition and represent a spectrum of changes. [1] It is different from renal lipomas which are neoplastic, whereas this condition is thought to be a degenerative process. [3],[4] Renal sinus lipomatosis, the mildest form is usually seen in the sixth and seventh decade associated with obesity, atherosclerosis or use of exogenous steroids. [1],[3] It has no clinical significance. Increased proliferation in the renal sinus exerts a mass effect on the intrarenal collecting structures, infrequently producing symptoms of obstruction. [2] At the other end of the spectrum is RRL where the entire renal parenchyma is replaced with adipose tissue, usually secondary to renal calculus and renal tuberculosis in 70% of the cases and occasionally after renal infarction. [1],[2],[3],[4] Usually it is unilateral in occurrence and rarely idiopathic. [1],[2] We feel that our case was of idiopathic variety as none of these etiological factors were detected in our case in the past or present either clinically or radiologically and neither the patient was obese. Two theories have been proposed for its pathogenesis. Some suggest a compensatory mechanism in which the adipose tissue occupies the space that is produced by the atrophied or destroyed kidney or there is an inflammatory induction of fatty proliferation to compensate for renal tissue loss. [2]

In this case the patient presented in the fifth decade, which is the recorded age group, though it has also been reported in a young patient in second decade with posterior mediastinal lipomatosis. [1],[4] The usual complaint in literature is flank pain, dull aching, and non-radiating which was seen in the present case. [1],[2],[4] They can also present with complaints of urinary tract infections due to urinary stones or mass in the abdominal cavity. [3] Blood urea nitrogen and serum creatinine is usually within the normal limits, though in our case, it was elevated. [4] They are normal if the disease is unilateral with other well functioning kidney. CT scan can confirm the fatty infiltration in the kidney and its distribution. [2] In this case, the fatty infiltration on CT scan had led to the radiological diagnosis of lipomatous tumor. Xanthogranulomatous pyelonephritis and fat-containing neoplasms including lipoma, liposarcoma, and angiomyolipoma are the usual differential diagnosis reported in the literature with imaging techniques. [2],[3] The latter group can be excluded by absence of parenchymal atrophy. Ultrasonography may suggest the diagnosis by demonstrating parenchymal atrophy or a hyperechoic renal sinus mass with a stone; however, it is not diagnostic. CT scan and magnetic resonance imaging scan appear to be an accurate method for demonstrating the distribution of adipose mass within the renal sinus and perirenal space. [2]

Grossly the kidney can be enlarged or small in size with markedly atrophic renal parenchyma and is usually associated with hydronephrosis as seen in our case. [3],[4] The shape of the kidney is always maintained. Histologically, this condition shows mature adipose tissue replacing the renal parenchyma leading to its atrophy. There can be sharp demarcation between the adipose tissue and the preserved renal parenchyma as seen in this case. [4] A major differential diagnosis in the presence of long standing inflammation and chronic calculus disease is xanthogranulomatous pyelonephritis. It is a chronic form of inflammation and shows characteristic xanthoma cells which was not seen in our case. However, the two conditions are also known to co-exist. [2],[5]

In conclusion, the important aspect of this case is that RRL is a relatively uncommon entity and may be confused with renal neoplasms on radiology. It is associated with a poorly or non-functioning kidney and histologically there is gradual replacement of the renal parenchyma with mature adipose tissue leading to end stage renal disease. Renal replacement lipomatosis may be missed if not considered due to lack of experience, so we hope that more urologists, radiologists, and pathologists become aware of this entity and recognize it.

 
   References Top

1.Setty NHA, Uma K, Narvekar VN, Desai RS. Bilateral Idiopathic Replacement Lipomatosis of the kidney with Posterior Mediastinal Lipomatosis. Indian J Radiol Imaging 2002;12:251-2.  Back to cited text no. 1    Medknow Journal  
2.Kocaoglu M, Bozlar U, Sanal HT, Guvenc I. Replacement lipomatosis: CT and MRI findings of a rare renal mass. Br J Radiol 2007;80:e287-9.   Back to cited text no. 2      
3.Xu Y, Liu RL, Zhang ZH, Zhao WM, Yang QC. Renal replacement lipomatosis. Eur Surg Res 2006;38:385-7.   Back to cited text no. 3      
4.Peacock AH, Balle A. Renal lipomatosis. Ann Surg 1936;103:395-401.  Back to cited text no. 4      
5.Prasad KK, Pandey R, Kathuria M, Pradhan PK. Co-existent massive renal replacement lipomatosis and xanthogranulomatous pyelonephritis: A case report. Indian J Pathol Microbiol 2003;46:674-5.  Back to cited text no. 5      

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Correspondence Address:
Vinaya B Shah
Flat No: 38, Bldg 2, Govt Quarters, Next to Race Course, K K Marg, Haji-Ali, Mumbai-400 034
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0377-4929.56163

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    Figures

  [Figure 1], [Figure 2]

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