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ISSN: Print -2349-0977, Online - 2349-4387

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Year : 2017  |  Volume : 4  |  Issue : 3  |  Page : 189-191

Renal sinus lipomatosis in transplant kidney

MRI Division, Dr. Gulati Imaging Institute, New Delhi, India

Date of Web Publication30-Jan-2018

Correspondence Address:
Parveen Gulati
MRI Division, Dr. Gulati Imaging Institute, J-16, Hauz Khas Enclave, New Delhi
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/astrocyte.astrocyte_74_17

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Renal sinus lipomatosis is a rare entity where there is abnormal proliferation of sinus fat. Fat proliferation can also occur in perinephric and periureteric regions. It is a benign condition which does not give rise to symptoms or any renal impairment. However, severe form of this condition, i.e. renal replacement lipomatosis, leads to atrophy of renal parenchyma, thereby leading to impairment of renal functions. Here, we report a case of renal sinus lipomatosis in a transplanted kidney, which is even rarer and has been reported in less than 10 previously reported cases in the English literature.

Keywords: Kidney transplant, lipomatosis, renal sinus lipomatosis

How to cite this article:
Aggarwal A, Gulati A, Gulati P. Renal sinus lipomatosis in transplant kidney. Astrocyte 2017;4:189-91

How to cite this URL:
Aggarwal A, Gulati A, Gulati P. Renal sinus lipomatosis in transplant kidney. Astrocyte [serial online] 2017 [cited 2022 May 29];4:189-91. Available from: http://www.astrocyte.in/text.asp?2017/4/3/189/224199

  Introduction Top

Renal sinus lipomatosis is a rare entity where there is abnormal proliferation of sinus fat. The condition is benign and does not cause any impairment of renal function. There exact pathogenesis is unknown. It needs differentiation from other fat containing tumors of kidney. The distinction can be accurately done with cross sectional imaging and thus can obviate the need of biopsy. A close follow up, however, is essential as excessive proliferation of sinus fat can replace the normal renal parenchyma (RRL) and deteriorate the renal function. We report a case of RSL in a transplant kidney, which is extremely rare.

  Case Report Top

This is a case of a 56-year-old female who had undergone renal transplant in 2012 for chronic renal parenchymal disease. During a routine follow-up, renal function tests were normal, however, sonography showed a hyperechoic mass arising from the lower pole of the transplanted kidney which did not show any significant internal vascularity. Size and echo texture of the kidney was otherwise normal.

To further characterize the mass, a noncontrast magnetic resonance imaging (MRI) was performed on a 3.0-T MRI scanner. T1W Turbospin echo, T2W Turbospin echo, T1W Fat saturation sequences were obtained which revealed excessive fat proliferation in renal sinus, as evidenced by T1 hyperintensity insinuating the renal sinus with suppression on FATSAT images [Figure 1]a and [Figure 1]b. No heterogeneity of the lesion was seen. No septation or solid tissue was seen. Mild caliectasis was present, predominantly of the upper pole. Cortical thinning was present in the lower pole of the transplanted kidney. However, perinephric fat was normal. No significant lymphadenopathy was seen in the abdomen.
Figure 1: Axial T1 weighted images through the transplant kidney showing T1 hyperintense soft tissue (a) insinuating and distending the renal pelvis. There is suppression of the hyperintense signal of soft tissue on FATSAT images (b). There is also thinning of the lower pole parenchyma.

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  Discussion Top

Renal sinus lipomatosis (RSL) is an extremely uncommon entity in a transplant kidney, which was first described in 1979 by Kaude et al.[1] In RSL, there is moderate proliferation of sinus fat due to an unknown trigger. Usually, it is asymptomatic and does not impair the renal function. However, the severe form is RSL,[2] where there is excessive proliferation of sinus fat to the extent that it replaces the renal parenchyma and severely impairs the renal function.

This entity needs to be differentiated from other fat-containing tumors affecting kidney. Lipoma can be differentiated from the former by its well-encapsulated nature. Liposarcoma is a malignant fat containing tumor which is located more peripherally, does not distort the renal parenchyma, and shows heterogeneity in the form of solid nodule or septation. Angiomyolipoma contains microscopic fat, is a ball type of a lesion, and is heterogenous and extremely vascular. Post-transplant lymphoproliferative/lymphoproliferation disorder (PTLD) is seen as ill-defined T2 hypointense lesion.

Various causative factors have been postulated to attribute to fat proliferation such as prolonged steroid administration, recurrent urinary tract infection, ageing, renal calculus disease, obesity etc.; however, its exact pathogenesis is yet to be established.

Several patients with renal transplant are exposed to high doses of steroids for long duration but all do not develop this condition on follow-up.

In one of the previously mentioned case report, there was improvement of renal function and hydronephrosis after administration of steroids. They hypothesized that fat proliferation occurs in response to some inflammatory trigger. As steroid administration resolved the inflammatory process, there was improvement in renal function.

In another study of 3 cases by Laouad et al., this entity occurred in patients of delayed graft function, recurrent urinary tract infections, and multiple rejection episodes, all of which are proinflammatory. The period between development of RSL and renal transplant is variable, ranging from 6 months to 8 years.[3] A case was described in 2002 by Maria Aurora,[4] which showed RSL in a case of borderline rejection developed after 7 years of renal transplant. In our case, it developed after 5 years.

RSL can be screened by ultrasound where it appears as an echogenic mass in renal sinus/medulla without any significant internal vascularity. Confirmative diagnosis can be accurately made by cross-sectional imaging, either by computed tomography scan or MRI. In CT, fat attenuation soft tissue is seen in renal sinus with preserved renal parenchyma. The fat proliferation can also occur in perinephric and periureteric region. On MRI, ill-defined soft tissue which is T1/T2-weighted hyperintense and suppression on fat saturation images confirms the diagnosis. In our case, suspicion of neoplastic mass was raised on ultrasound, which was characterized as RSL on MRI.

  Conclusion Top

RSL is an uncommon condition in normal kidney and is even rarer in a transplant kidney. To the best of our knowledge only three papers with a total of five cases have been reported. It is necessary to have complete knowledge of this condition to diagnose it accurately and obviate the need of biopsy. However, it requires close follow-up as the condition may transform to renal replacement lipomatosis which can severely deteriorate renal function.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that name and initial will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Kaude JV, Fuller TJ, Soong J. Fibrolipomatosis of the transplanted kidney. Rofo 1979;130:300-2.  Back to cited text no. 1
Khan M, Nazir SS, Ahangar S, Farooq Qadri SJ, Salroo NA. Total renal replacement lipomatosis. Int J Surg 2010;8:263-5.  Back to cited text no. 2
Laouad I, Büchler M, Weestel PF, Lebranchu Y, Legendre C, Choukroun G, et al. Replacement kidney lipomatosis after renal transplantation. Transplantation 2005;79:496-8.  Back to cited text no. 3
Posadas MA, Chua E, Thomas B, Savage SJ, Baliga P. Allograft dysfunction in a patient with an odd-looking kidney: Case of renal lipomatosis and review of literature. Clin Kidney J 2012;5:359-61.  Back to cited text no. 4


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