The most common extraintestinal manifestations of Crohn's disease involve the eyes, skin, hepatobiliary tract, and the musculoskeletal and respiratory systems. Mass-forming granulomatous inflammation in extraintestinal organs is extremely rare and there are only a few reports of patients with Crohn's disease presenting with inflammatory pseudotumours of the liver, pancreas and kidneys. We present a case of a mass-forming renal granulomatous inflammation in an adult female with Crohn's disease. The clinical, pathological and imaging features of this case illustrate that renal inflammatory pseudotumour is a rare but important differential diagnosis of a renal mass in patients with Crohn's disease and that radiologists should be aware of its existence when considering other more common pathologies, such as focal pyelonephritis and renal tumours. Renal inflammatory pseudotumour may have relatively non-specific imaging features and a biopsy may be required to make the diagnosis.