Background: Idiopathic retroperitoneal fibrosis is an infrequent process of unknown aetiology characterised by fibrous tissue proliferation in the retroperitoneum. Even less frequent is a localized form of this disease by a proliferation of fibrous tissue around single or both kidneys.

Case report: We describe a case of 46-year old man in whom medical management was started for accidentally discovered arterial hypertension, which turned out to be difficult to control.   During diagnostic work-up of hypertension, an abdominal ultrasound was obtained a year later demonstrating slight bilateral caliectasis without obvious visible cause for it. Laboratory exams have shown significantly impaired renal function, normocytic anaemia, slightly higher sedimentation rate, increased CRP and normal urinalysis. Nephrologist has decided for hospitalisation during which magnetic resonance imaging was performed  showing a few mm wide tissue coats surrounding both kidneys with fluid lying between the coat and kidney capsule. A biopsy of perirenal mass has confirmed a dense cellular lesion consisted of interweaved fascicles of spindle-shaped cells. After exclusion of tumours and other causes, a diagnosis of retroperitoneal fibrosis was confirmed. Clinical picture and laboratory data corresponded to idiopathic form of this disease. A treatment with tamoxifen was started after patient refused treatment with methylprednisolone. During tamoxifen monotherapy, there was gradual significant improvement of general symptoms, notable decline in inflammation markers, improvement of anaemia, normalisation of kidney function, and normalisation of blood pressure.

Conclusion: Retroperitoneal fibrosis is still an obscure and multifaceted disease. A proper selection of diagnostic methods is the key to correct and fast diagnosis as well as good grounding for proper treatment.