Quality of same-day CT colonography following incomplete optical colonoscopy
O’Shea, A., Foran, A. T., Murray, T. E., Thornton, E., Dunne, R., Lee, M. J., & Morrin, M. M. (2020)
European Radiology, 30(12), 6508-6516. https://doi.org/10.1007/s00330-020-06979-3
Performing a complete colonoscopy is vital for identifying colorectal malignancy and minimising polyp miss rates in all segments of the colon1. Unfortunately the success of colonoscopy is dependent on several factors including adequate bowel preparation and patient tolerance2. Estimated rates of incomplete colonoscopy vary between 4 and 24%1. Thankfully, CT colonography (CTC) is not as significantly limited by these factors. ESGAR consensus guidelines now state that CTC is the recommended tool for imaging the colon in the setting of incomplete endoscopic colonoscopy3-5. Increasingly centres with capacity can offer patients CT colonography on the same day or next day following incomplete optical colonoscopy, but there have been some questions regarding the quality of these studies6.
A group of radiologists at the Beaumont hospital in Dublin conducted a retrospective review of 245 patients who underwent same-day CT colonography following an incomplete optical colonoscopy, in order to study the diagnostic quality of these scans.
Following incomplete colonoscopy, patients underwent a low dose non-contrast CT scan of the abdomen and pelvis to exclude a perforation. Once they had recovered from any sedation administered at the time of colonoscopy faecal tagging was commenced using 30mL Gastrografin in 1 pint of water, consumed over 20 minutes. CTC was scheduled for approximately 3 hours later.
In order to evaluate the quality of the same-day CTC studies, the colon was divided into thirteen sections extending from rectum to caecum. Each section was evaluated for adequacy of luminal distension, residual fluid volume and density, residual stool, and adequacy of faecal tagging. A scoring system was devised by a consultant radiologist, then taught to and employed by a single radiology fellow who reviewed all 245 scans. Scores for each aspect of diagnostic quality were allocated to each of the thirteen sections of the colon.
Results showed that the median residual volume of fluid in each examined segment was estimated at less than 25%, and the mean score for tagging of residual fluid was between 0 (complete) and 1 (incomplete but adequate). Minimal residual stool was noted in the large bowel and, when present, was most frequently identified in the rectum or proximal sigmoid colon. Finally, luminal distension in all segments showed median values ranging from 3 to 4 on the semi-quantitative scale, indicating either “entire segment seen” or “well distended”. Contrast reached, at least, the left hemi-colon in 84% of patients and the rectum in 57% of patients. Perhaps most importantly, 99% of studies did not require a repeat CTC or optical colonoscopy.
Overall the results give strong evidence for the concept that same-day CT colonography is a high quality study which can provide complete colonic evaluation following an incomplete colonoscopy.
The benefits of offering same day CTC to patients who undergo incomplete colonoscopy are clear. Patients are saved having to present for another appointment, and enduring the uncomfortable process of bowel preparation for a second time. The study recognises this method’s potential to reduce patient ‘attrition’, by which a proportion of patients may never return for a repeat study, potentially leading to a delayed or missed diagnosis.
Whilst the results of this study are impressive, it somewhat limited by the nature of its design as a retrospective, observational study. It would be interesting to see a matched cohort study comparing same day CTC scan quality with a group of patients undergoing CTC as their first test. A clever scoring system was devised as an attempt to categorise subjective parameters such as luminal distension, however a single radiology fellow evaluated all the scans, potentially introducing a degree of observer bias. Finally, the use of a low-dose non-contrast CT scan to exclude a perforation prior to the CTC results in a higher radiation dose, perhaps unnecessarily given that no perforations were identified in any of the 245 studies.
This paper prompted intense discussion in our department when it was presented at the journal club meeting. The potential cost-effectiveness and patient-friendly advantages achieved by same-day CTC are a fantastic opportunity, but these must be weighed against a department’s capacity. The proportion of incomplete colonoscopies occurring during each endoscopy list would need to be determined in order to plan how many CT scan slots should be made available each day.
References:
- Franco DL, Leighton JA, Gurudu SR (2017) Approach to incomplete colonoscopy: new techniques and technologies. Gastroenterol Hepatol 13:476–483
- Sachdeva R, Tsai S, El Zein M et al (2016) Predictors of incomplete optical colonoscopy using computed tomographic colonography. Gastroenterol Hepatol (N Y) 22:43–49. https://doi.org/10.4103/1319- 3767.173758
- Neri E, Halligan S, Hellström M et al (2013) The second ESGAR consensus statement on CT colonography. Eur Radiol 23:720–729. https://doi.org/10.1007/s00330-012-2632-x
- Lara LF, Avalos D, Huynh H et al (2015) The safety of same-day CT colonography following incomplete colonoscopy with polypectomy. United European Gastroenterol J 3:358–363. https://doi.org/10.1177/2050640615577881
- Yucel C, Lev-Toaff AS, Moussa N, Durrani H (2008) CT colonography for incomplete or contraindicated optical colonosco- py in older patients. AJR Am J Roentgenol 190:145–150. https:// doi.org/10.2214/AJR.07.2633
- Theis J, Kim DH, Lubner MG, del Rio AM, Pickhardt PJ (2016) CT colonography after incomplete optical colonoscopy: bowel preparation quality at same-day vs. deferred examination. Abdom Radiol (NY) 41:10–18. https://doi.org/10.1007/s00261-015-0595-5
Donal Bradley is a clinical radiology fellow in St. James’ University Hospital in Leeds, UK. He is a fellow of the Royal College of Radiologists and an ESGAR member. Having completed his training in Manchester, he is undertaking a fellowship in gastrointestinal radiology.
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