# Retroperitoneal lipoma Retroperitoneal lipoma The patient may seek advice on account of a swelling or because of indeļ¬nite abdominal pain. The swelling sometimes reaches an immense size. Diagnosis is usually by CT scan. A retroperitoneal lipoma sometimes undergoes myxomatous degeneration, a complication that does not occur in a lipoma rance. Figure 65.22 Representative sagittal computed tomography recon - struction of a right-sided psoas abscess (arrow) (courtesy of Dr K Patel, Homerton University Foundation Trust, London, UK). size is often malignant (liposarcoma).