Introduction Colonoscopy is often the first line investigation for detection of lesions within the large bowel and remains the gold standard in investigating for suspected colon cancer. However if endoscopy is either incomplete, determined too hazardous or declined computed tomographic colongraphy is the next investigation of choice.¹ One of the additional and potentially beneficial features of CT is in the detection of extracolonic lesions, with studies suggesting approximately 40% of scans reveal one or more extracolonic abnormality including 14% detecting ‘significant findings’ requiring further investigation.²

Methods We performed a retrospective analysis of all patients undergoing CT imaging of the large bowel, both CT colonography or plain abdominal CT (if CT colonography was not possible) at one south London hospital in a 13 month period between 2012–2013. Any extracolonic findings were determined either significant, where requiring further investigation or treatment, or insignificant by the reviewer. Any subsequent outcome of the significant findings was also sought.

Results A total of 257 scans were reviewed comprising of 250 (97%) CT colonography and 7 (3%) plain abdominal CTs in 104 (40%) male and 153 (60%) female patients. The average age was 68 years (range 39–91). A total of 163 (63%) of scans detected at least one extracolonic finding, with 55 (21%) of these significant. Sites included 13 liver, 7 lung, 6 pancreatic, 5 renal and 5 adrenal. Further investigation based on these findings revealed 5 (1.9%) malignancies. One patient was found to have a renal cell carcinoma and went on to have curative surgery. One patient was diagnosed with pancreatic cancer and one with hepatocellular carcinoma, both of which were managed palliatively, and one patient was found to have peritoneal recurrence of a previously treated colonic adenocarcinoma. One scan discovered lung and liver metastases along with the causative colonic primary. Other notable findings included a 5.3cm AAA and a pulmonary embolus seen in a segmental lower lobe pulmonary artery. There were a 209 insignificant findings in 139 (54%) of the CTs, with a maximum of 5 in a single scan.

Conclusion This study helps to highlight the potential additional benefit of CT colonography over endoscopic visualisation of the large bowel. The prevelance of extracolonic findings in this cohort was high, in keeping with previous studies, with CT colonography having value is its detection of extracolonic malignancies, staging and other serious conditions. However there was also a substantial rate of additional investigation for subsequently benign findings.

References

1. Taylor SA et al. Guidelines for the use of imaging in the NHS Bowel Cancer Screening Programme: Second Edition. 2012

2. Xiong T et al. Br J Radiol 2005 Jan;78(925):22–9

Disclosure of Interest None Declared.