Retroperitoneal fibrosis misinterpreted as an abdominal aortic aneurysm on ultrasound.

1 of 2 DESCRIPTION A 57-year-old Polish gentleman presented with persistent upper abdominal pain exacerbated by eating. Abdominal ultrasound scan performed in Poland showed a 4.4 cm mass in the region of the abdominal aorta reported as an abdominal aortic aneurysm. Subsequent CT imaging demonstrated a normal calibre aorta, surrounded by a soft tissue mass in conjunction with left-sided hydronephrosis ( fi gure 1 ). Erythrocyte sedimentation rate was raised at 99 mm/h and C-reactive protein was 43.3 mg/l. Renal function was also deranged (urea 8.7 mmol/l, creatinine 162 umol/l). A diagnosis of retroperitoneal fi brosis (RPF) was made. The patient was referred for ureteric stenting and commenced on prednisolone. Retropertioneal fi brosis is a rare fi brotic reaction, which has an annual incidence of one per 200 000. 1 Around 70% of cases are idiopathic but other causes include malignancy, infl ammatory periaortitis, retroperitoneal trauma, autoimmune disease, irradiation and certain medications (eg. β-blockers, methysergide, methyldopa). 1 The commonest presenting symptoms of RPF are abdominal pain (38%) or back pain (40%). 2 The diagnosis of RPF is often delayed because patients are asymptomatic or symptoms are masked by concomitant disease. 3