Presentation
Chronic renal disease presenting with left flank pain and increased serum creatinine. Prior ultrasound revealed an amorphous heterogeneous large mass with non-visualization of left kidney.
Patient Data
There is complete loss of normal architecture and shape of left kidney, with extreme parenchymal atrophy and fibrosis. Marked fatty proliferation is seen in renal sinus, hilum and perinephric space forming an encapsulated mass measuring 13.4 x 12.2 cm. A large staghorn calculus measuring 35 x 26 mm is seen in left renal parenchyma. In the setting of obstructive uropathy, imaging features are suggestive of replacement lipomatosis of kidney.
Right kidney appears normal.
Case Discussion
Replacement lipomatosis or fibrolipomatosis is an extremely rare condition, characterized by fibro-fatty proliferation of renal sinus tissue and replacement of normal renal parenchyma with fibrous and adipose tissue. This particular patient has type-II diabetes mellitus and chronic nephropathy with longstanding left sided obstructive uropathy. Pre-existing obstructive uropathy is associated with 70% cases of replacement lipomatosis of kidney 1. Usually the condition is unilateral, but can occur bilaterally 2.
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