Deb Kumar Boruah1, Arjun Prakash2, Sashidhar Achar3, Shantiranjan Sanyal4, Simanta Jyoti Nath5

Renal replacement lipomatosis is an uncommon benign entity where abundance of fibrofatty tissue proliferation occurs in renal sinus with further extension of proliferated fatty tissues into renal hilum, perinephric and periureteric spaces. It is usually associated with renal atrophy and marked renal parenchymal destruction. Aim of our study was cross-sectional imaging evaluation of Renal Replacement Lipomatosis (RRL).
A hospital based cross-sectional retrospective study was conducted. The study group comprised of 16 patients presenting to the Departments of Radio-diagnosis, Surgery and Urology in a tertiary care hospital from May 2014 to April 2016. All patients were initially evaluated clinically and ultrasonographically followed by cross-sectional imaging modality like Computed Tomography (CT), Magnetic Resonance Imaging (MRI) or both.
Out of 16 patients of renal replacement lipomatosis, 15 patients (93.8%) had associated renal pelvic or ureteric calculus while 1 patient (6.2%) had left para-aortic mass without associated calculus. Out of fifteen patients of calculus related RRL, 8 patients (53.3%) had calculus size more than 40 mm, followed by 4 patients (26.7%) who had size from 20 to 40 mm and 3 patients (20%) had size less than 20 mm. The mean CT HU value of calculus was 1334±84.5 in our study. Three patients (18.8%) had only renal hilar fatty excessive deposition, 1 patient (6.2%) had renal hilar and perinephric space fat depositions, 3 patients (18.8%) had renal hilar, perinephric and periureteric spaces depositions and 9 patients (56.2%) had renal hilar and periureteric excessive fatty depositions. Delayed renal functioning was noted in 9 patients (56%), followed by non-functioning in 5 patients (31.2%) and 2 patients (12.5%) had normally functioning kidneys.
Cross-sectional imaging like CT and MRI scan helps in diagnosing RRL and proper delineation of extensions of excessive fatty tissue proliferation.