Vicarious renal excretion of iodinated contrast introduced into the bowel is a known phenomenon that has rarely been reported. In clinical settings like Crohn's disease in which evaluation for recto-vesical fistula is frequently requested, vicarious excretion can cause misapprehension and error in diagnosis. We present a case of Crohn's disease in which gastrografin enema was performed to evaluate for fistula and initial interpretation was mistakenly positive, however, simple methods of elucidation were utilized to prevent error in diagnosis.