Retroperitoneal panniculitis: Rare diagnosis or beginning of retroperitoneal fibrosis?

Retroperitoneal panniculitis is a very rare cause of retroperitoneal soft tissue masses with consecutive ureteric obstruction. Typical findings a re abnormal perinephric soft tissue density with linear strands in the computerized tomography as well as unregular bilateral impression of the ureter without medialisation, noticable in the retrograde pyelography. Most of the times, the etiology of the disease remains unclear and the outcome of cases with idiopathic retroperitoneal panniculitis is uncertain. Spontaneous resolvement is known as well, as chronic development even under medical treatment. Nevertheless, in cases with very fast progression, highdose steroid-therapy should be initiated and fast relief of renal obstruction by ureteral stents or nephrostomy should be performed.