Granulomatous prostatitis: A pitfall in endorectal MR imaging and 3D MR spectroscopic imaging

Granulomatous prostatitis is a benign inflammatory condition of the prostate which can be mistaken for prostatic carcinoma both clinically and on imaging findings. In MR imaging, granulomatous prostatitis has been shown to cause signal intensity decrease in the prostatic peripheral zone similar to carcinoma on T2-weighted sequences. The recent introduction of 3D MR spectroscopy (3D MRS) into clinical practice adds information to the morphological data of endorectal MRI, enabling a more accurate localization and diagnosis of prostate cancer and chronic prostatitis. We describe two cases which had been diagnosed, respectively, 15 and 18 months earlier with transitional cell carcinoma of the bladder. They had subsequently been treated with a regimen of intravescical bacilli Calmette-Guerine (BCG). These two patients underwent combined endorectal MRI and 3D MRS imaging of the prostate in which findings were suggestive of prostatic carcinomas instead histological exam showed to be granulomatous prostatites.