Renal replacement lipomatosis is a rare condition characterised by fatty tissue proliferation in renal sinus and perinephric space with marked destruction/atrophy of renal parenchyma (due to chronic inflammation).
It has been associated with ageing, calculus disease (nearly 70% of cases), renal tuberculosis and post transplantation. It may also be associated with fibrotic changes to varying degree.
An advanced stage of xanthogranulomatous pyelonephritis is another common association.
It is considered to be on the extreme end of a spectrum with renal sinus lipomatosis being the mildest form. The condition is usually unilateral.
Patients usually present with non-specific complains like flank pain, fever and weight loss. Sometimes patient may directly complain of a vague flank mass.
Usually shows calculi and displacement of bowel.
It is usually difficult to come to a diagnosis on ultrasound alone but it may show echogenic mass suggestive of fatty tissue and calculi in the atrophic renal tissue.
It is diagnostic and shows typical features including:
- renal parenchymal atrophy/destruction
- perinephric and hilar lipomatosis
- renal calculi
- perinephric abscesses which may extend to psoas muscle
Possible differential considerations include
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