Idiopathic renal replacement lipomatosis: A case report and review of literature

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.

Idiopathic renal replacement lipomatosis: A diagnostic and therapeutic challenge

“…Xanthogranulomatous pyelonephritis is the closest mimicker of this condition, especially in case of calculus. The absence of xanthoma cells confirms diagnosis in favor of renal replacement lipomatosis (2,4).…”

“…Although it is easy to diagnose a fatty mass on CT, to characterize this entity preoperatively as renal replacement lipomatosis is a clinical challenge. In almost all reported cases, the diagnosis was confirmed on histopathology only (1)(2)(3)(4)(5)(6). Hence, the best treatment in such cases is excision of fatty mass intotal.…”

Renal replacement lipomatosis - A rare but also underdiagnosed entity

“…It is different from renal lipomas in which adipocytes proliferation is in association with normal renal parenchyma. 2,3,5 Renal sinus lipomatosis, is usually seen in the sixth and seventh decade associated with obesity or use of steroids or idiopathic conditions. It is usually secondary to renal calculus in 70% of the cases and occasionally after renal infarction.However, some RRL cases are also reported in associations with aging, renal tuberculosis and post renal transplantation.…”

Asymptomatic Urolithiasis Complicated by Nephrocutaneous Fistula

“…[13] This benign condition is characterized by the replacement of normal renal parenchymal tissue by the proliferation of sinus and perirenal fatty tissue, secondary to severe renal atrophy. [14] Renal replacement lipomatosis is seen in 70% of cases with renal calculus, less frequently renal tuberculosis, and occasionally after renal infarction,[1516] associated with hydronephrosis and inflammation. The differential diagnosis for renal replacement lipomatosis is fatty renal masses (liposarcoma, lipoma, angiomyolipoma), transitional carcinoma of the renal sinus, and xanthogranulomatosis pyelonephritis.…”