Unusual abdominal masses

A 66-year-old afebrile man presented with a 10-day history of general fatigue. He had a history of autoimmune pancreatitis and tubulointerstitial nephritis diagnosed from a kidney biopsy of the left kidney. He had been treated with oral glucocorticoids (prednisolone 25 mg/day) for 3 months. He had normal hepatic function, renal insufficiency (creatinine 122 lmol/L) and a leucocyte concentration of 31.4 3 10/L with predominant neutrophils. There were no abdominal symptoms. An emergency computed tomography (CT) scan was performed to determine the cause of the inflammation. The CT scan revealed a large solid mass in the pelvis and a solid mass in the right retroperitoneal space (Figure 1A and B, indicated by arrows). Gram staining of the grey fluid aspirated from the right retroperitoneal mass (Figure 1C) revealed positive branching rods suggestive ofActinomyces (Figure 1D). We cultured the organism and identified Actinomyces. Intravenous cefotaxime was started, as our patient’s bacterium was ampicillin resistant, and treatment was continued for