Renal replacement lipomatosis of the right kidney.

To cite: Ratkal V, Chawla A, Mishra DK, et al. BMJ Case Rep Published online: [please include Day Month Year] doi:10.1136/ bcr-2014-208701 DESCRIPTION Renal replacement lipomatosis (RRL) of the kidney, also known as replacement fibrolipomatosis, is an advanced form of renal sinus lipomatosis that usually occurs unilaterally. Infection, long-term hydronephrosis and calculi are associated with severe renal parenchymal atrophy followed by replacement of fat in renal sinus, hilum and perirenal spaces. 2 It occurs in the 6th and 7th decade. 4 Pathologically, the kidney is enlarged with normal shape and has a gross, fibrofatty appearance. The renal cortex is atrophied, with varying degrees of hydronephrosis or pyonephrosis and calculi. Microscopically, marked proliferation of fat in the renal sinus, with extremely large fat cells not permeating the renal parenchyma is seen. CT scan is the most accurate method of demonstrating the distinctive features of RRL. The abundant fatty tissue, characteristic distribution of fat within renal sinus and perinephric space with calculi and atrophied parenchyma can be easily appreciated. The kidney is non-functional and