Abdominal ultrasound after colonoscopy with insufflation of air versus carbon dioxide – a randomised double blind trial

Aims: Colonoscopy is dependent on insufflation of gas to visualize the anatomical and pathological structures. Former trails have shown that air leads to abdominal pain but carbon dioxide reduces pain after colonoscopy significantly. It is often useful to combine abdominal ultrasound with colonoscopy. Study hypothesis: carbon dioxide under colonoscopy minimises examination related symptoms and gives better ultrasound conditions than air.

Double blind trial: 30 patients were randomised to carbon dioxide insufflation (n=15, 7 men and 8 women, average age 50 years) or air (n=15, 6 men and 9 women, average age 53 years). 30 minutes after colonoscopy abdominal symptoms were registered. Visual analogue scale was used. Afterwards abdominal ultrasound was performed. Ultrasound quality of the liver, gall bladder, biliary ducts, pancreas, spleen, kidneys, abdominal vessels, antrum, bowel, urinary bladder and prostate/uterus was observed. Ultrasound quality was registered in four categories 0 (god)-3 (bad conditions).

Results: There was no significant difference between carbon dioxide and air according to symptom score. However, the average ultrasound quality was significantly improved after carbon dioxide supported colonoscopy: 14,73±12,37 versus 29,9±13,97, P<0,003.

Conclusion: In this study, we found that using carbon dioxide instead of air improved the quality of abdominal ultrasound after colonoscopy remarkably. Sometimes it is useful to supply colonoscopy with immediate ultrasound (e.g. in the case of stenosis, unsatisfactorily cleansed bowel, abdominal metasases). In these cases the use of carbon dioxide improves image quality.