An unusual abdominal mass in a renal transplant recipient

Renal transplant recipients are at increased risk of malignancy and infection. We present the case of a 72-year-old-man with recurrent bladder carcinoma, abdominal aortic aneurysm repair, and end-stage renal failure due to renovascular disease. He received a cadaveric renal allograft into his left iliac fossa, was given cyclosporin A, azathioprine, and prednisolone triple therapy immunosuppression, and had no rejection episodes. He presented four years post-transplantation with a two-year history of intermittent sweats and fevers. Previous episodes had been investigated with no firm diagnosis made. This time he had right iliac fossa pain of three weeks' duration. Examination revealed a tender mass. Investigations showed unchanged graft function, but elevated inflammatory indices. Ultrasonography and computed tomography detailed an infiltrating mass associated with the sigmoid colon, which colonoscopy failed to visualise. At laparotomy a 6-cm tumor was removed, with adherent sigmoid colon and bladder dome. Macroscopically the mass was an abscess, and microscopy found acute and chronic inflammatory giant cells and fibrillary masses suggestive of actinomycosis, with no malignancy. The patient recovered uneventfully on antibiotics. At six months' follow-up, examination, inflammatory markers, and radiographic imaging showed no evidence of recurrence. Twelve months later the patient died of rupture of his proximal abdominal aorta. There was no evidence of recurrence at postmortem examination. We conclude with a brief review of actinomycosis in transplant recipients.