Retroperitoneal fibrosis-the long and winding path.

Retroperitoneal fibrosis (RPF) is a rare systemic disease. Two-third of the cases are idiopathic but assumed to have autoimmune process related to IgG-4. It is often a diagnosis of exclusion due to its non-specific clinical presentation. Early manifestation commonly causes back pain, raised erythrocyte sedimentation rate level and renal impairment. Investigations of choice are MRI and contrast-enhanced CT but biopsy should be performed for diagnostic confirmation. This case report describes a delay in diagnosing RPF in a 57-year-old female who initially presented to primary care with back pain, mild anaemia, raised erythrocyte sedimentation rate and progressive renal function decline. She was seen urgently in haematology clinic who arranged bone scan to rule out osteoblastic metastases, finding demonstrated possible pelviureteric junction dysfunction. The investigation was followed by a MAG3 renogram 4 weeks later instead of an abdominal CT leading to diagnostic delay. She then presented acutely 1 day after renogram with life-threatening hyperkalaemia and AKI 3. RPF was then suspected. Renal ultrasound scan and CT scan consecutively showed bilateral gross hydronephrosis and retroperitoneal mass around the aorta. The pelviureteric junction dysfunction was due to ureters getting embedded into the dense retroperitoneal fibrous tissue. She subsequently underwent bilateral ureteric stent placement and was commenced on steroid therapy, with satisfactory outcome on follow-up. Laparoscopic retroperitoneal biopsy later confirmed the diagnosis. This case not only highlighted important learning points on the presenting features and radiographic findings of RPF, but also the clinician's cognitive biases leading to diagnostic delay of a rare but life-threatening disease.