Introduction: CT colonography (CTC) is widely accepted as a safe modality for colonic assessment. CTC is often utilised following an incomplete or failed colonoscopy however, may be considered in those who do not want a colonoscopy. Case: An 82-year-old female had a CTC for surveillance in the setting of severe multi-focal Crohn’s disease with manual insufflation via rectal tube. Immediate identification of extraluminal gas within the extra-peritoneal meso-rectal space suggested a perforation. The patient had two episodes of rectal bleeding but was otherwise well with no pain or other symptoms. She underwent an emergency flexible sigmoidoscopy which identified a 2cm perforation spanning from the dentate line proximally. The mucosa proximal to this appeared intact and healthy. A primary trans-rectal full-thickness repair was performed and the patient was discharged without complications. Discussion: The incidence of perforation in CTC is 0.04-0.1% and 22.2% occur in the rectum. The risk of perforation is higher in those with active inflammatory bowel disease (IBD). 44.9% of patients develop symptoms following perforation and only 37.8% require surgical intervention. The risk of perforation is higher with manual compared to automated insufflation as well as inadequately lubricated rectal tubes. Trans-anal repair of extra-peritoneal rectal perforations can be considered for early assessment and control of contamination. Conclusion: perforation albeit rare in CTC, remains a real risk and clinicians should be mindful in patients with risk factors. CTC should be avoided in patients with severe and active IBD.