Abstract
Colonoscopy is the gold standard technique for the diagnosis of colon and rectal cancers in the UK. It is routinely performed in hospitals across the NHS by both consultants (gastroenterologists or general surgeons) and trained nurse specialists, where if they perform at least one colonoscopy session a week, will perform approximately 250 colonoscopies a year. Caecal intubation rates, which are used as a marker for colonoscopy completion, are recorded with guidelines recommending that intubation should be achieved in over 90%. 1
With standards set for a frequently performed investigation that surgical planning is dependent on, it would be expected that colonoscopic localisation of colonic lesions would be accurate, but Johnstone and Moug's 2 work contradicts that, finding 19% of colonic lesions at colonoscopy to be anatomically elsewhere. This work is the most recent publication analysing colonoscopy accuracy and its findings are supported by older publications that document a wide range of accuracy from 59.5% to 96%. Although the majority of the inaccurately located lesions in Johnstone and Moug's work did not alter the planned surgical management because they were in anatomical areas that were already going to be resected as part of the planned operation, significant on-table alterations did occur in 6.3%. An example of one of these alterations is the finding of a colonic cancer in mid-transverse colon that was thought to be at the hepatic flexure. Although anatomically that does not sound significant, for the colorectal surgeon, the operation has changed from a right hemicolectomy to an extended right hemicolectomy with longer anaesthetic and surgical time. It is worth pointing out that all of the five patients who underwent on-table alterations had open procedures. If they had been laparoscopic then increased anaesthetic and surgical time, in addition to extra ports and potential conversion to open would need to be considered.
Many surgeons would probably think that the staging pre-operative CT scan would be helpful in lesion localisation, decreasing the pressure on colonoscopy to determine what type of colorectal resection need to be performed. However, as Johnstone and Moug have shown, the primary tumour cannot be seen in almost a quarter of scans, probably as a result of the NHS Bowel Screening Programme detecting earlier and therefore, smaller lesions. 3 This means that optimal pre-operative planning is still dependent on accurate lesion localisation at colonoscopy and it is likely to increase its reliance as the screening programme progresses through its cycles.
The authors only briefly discuss the potential influencing factors in colonoscopy lesion localisation as the study is powered for accuracy. Further work is underway that is analyzing potentially influencing factors with completion hopefully leading to the development of nationally adopted recommendations to improve lesion localisation at colonoscopy. Perhaps unsurprisingly, there may be a potential relationship with body habitus and inaccurate lesion localisation. In addition, incomplete colonoscopy due to obstructing or stenosing lesions appears to increase inaccurate lesion localisation, perhaps due to the colonoscopist not being able to see all the potential colonic landmarks that help with anatomically locating a lesion. In such cases, surgeons may want to consider the use of CT pneumocolon to provide supporting lesion localisation information. Indeed, the role of CT pneumocolon for lesion localisation has not been clearly defined. The last finding to comment on is that use of the magnetic scope guide, which one might expect to increase accuracy does not appear to be significant, which may reassure units where a scope guide is not readily available.
Johnstone and Moug's work have highlighted that factors need to be indentified that influence lesion localisation at colonoscopy. Modification of such factors should optimize pre-operative planning and subsequent patient outcomes after colorectal surgery in the modern era.