Renal replacement lipomatosis is a rare condition characterised by fatty tissue proliferation in the renal sinus and perinephric space with marked destruction/atrophy of renal parenchyma (due to chronic inflammation).
Patients usually present with non-specific complaints like flank pain, fever and weight loss. Sometimes a patient may directly complain of a vague flank mass.
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.
Usually shows calculi and displacement of bowel.
It is usually difficult to come to a diagnosis on ultrasound alone but it may show an 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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