Think Zebras, Not Horses: Bilateral Hydronephrosis due to Idiopathic Retroperitoneal Fibrosis Presenting as Diffuse Low Back Pain

BACKGROUND: Idiopathic retroperitoneal fibrosis (IRF) is a rare condition with reported incidence ranging from 0.1 to 1.3 per 100,000 person years. It commonly involves formation of fibrous tissue encasing the abdominal aorta and its branches extending into the retroperitoneal space. We present a case of back pain due to IRF in a middle-aged African American woman, leading to bilateral obstructive hydronephrosis. There are very few reported cases of IRF and the diagnosis of this condition is challenging due to its ambiguous symptoms.
CASE REPORT: Our patient initially presented with non-anginal chest pain, cough, and recent history of non-specific low back pain and was later found to have obstructive nephropathy secondary to IRF. Interestingly, ultrasonography was unable to identify the cause of bilateral hydronephrosis, and thus an abdominal CT was needed to make the diagnosis.
CONCLUSIONS: We aim to emphasize the importance of maintaining a high suspicion for IRF in a patient presenting with vague symptoms such as poorly localized low back pain, with abnormal renal function and signs of obstructive uropathy. Early recognition and treatment of IRF is important to prevent irreversible organ damage.

Keywords: Back Pain, Hydronephrosis, Retroperitoneal Fibrosis