Water infusion versus air insufflation for colonoscopy

Colonoscopy is a visual examination of the inner lining of the large intestine with a camera on a flexible tube passed through the anus. Colonoscopy can provide a visual diagnosis of colorectal diseases. In particular, colonoscopies are an important tool in screening for colorectal cancer, and are the gold standard for the early detection of tumours and polyps located in the intestinal wall. Polyps may develop into colorectal cancer and a standard procedure is to remove these if identified, Colonoscopy allows the removal of polyps, sparing the need for open surgery.

The degree of colorectal cancer protection offered by colonoscopy depends on the technical performance. For example, it is important that colonoscopy is performed through the whole length of the colon, allowing for examination of all the colonic segments. Another measure of the quality of a colonoscopy is whether it can detect a lesion in the colon, such as adenomas.

Standard colonoscopy uses air insufflations to expand the lumen for better visualisation and facilitating advancement of the colonoscope through the large intestine. Recent clinical trials have proposed that using water instead of air insufflation may minimise patient discomfort and facilitate passage of the colonoscope through difficult segments of the large intestine. Moreover, water colonoscopy may remove residual faeces, thereby improving the view and the detection of adenomas.

The purpose of this review was to compare the effectiveness of the novel water infusion colonoscopy with the standard air colonoscopy.

We included 16 trials encompassing 2933 colonoscopies in this review. The review showed that completeness of colonoscopy was similar between water infusion and standard air insufflation, and that adenoma detection (participants with at least one adenoma detected) was improved with water colonoscopy (36% versus 31% in the air group).

In addition, participants experienced significantly less pain with water colonoscopy compared with the standard procedure.

Detection of cancer and precancerous lesions during standard colonoscopy is far from perfect. Improvements in adenoma detection by water infusion colonoscopy, although small, may help to increase the rate of adenoma detection. This may reduce the risk of colorectal cancer development after a colonoscopy without abnormal findings.

Authors' conclusions: 

Completeness of colonoscopy, that is cecal intubation rate, was not improved by water infusion compared with standard air insufflation colonoscopy. However, adenoma detection, assessed with two different measures (that is adenoma detection rate and number of detected adenomas per procedure), was slightly augmented by the water infusion colonoscopy. Improved adenoma detection might be due to the cleansing effects of water infusions on the mucosa. Detection of premalignant lesions during standard colonoscopy is suboptimal, and so improvements in adenoma detection by water infusion colonoscopy, although small, may help to reduce the risk of interval colorectal carcinoma. The most obvious benefit of water infusion colonoscopy was reduction of procedure-related abdominal pain, which may enhance the acceptance of screening/surveillance colonoscopy.

Read the full abstract...

Colonoscopy is a widely used diagnostic and therapeutic modality. A large proportion of the population is likely to undergo colonoscopy for diagnosis and treatment of colorectal diseases, or when participating in colorectal cancer screening programs. To reduce pain, water infusion instead of traditional air insufflation during the insertion phase of the colonoscopy has been proposed, thereby improving patients’ acceptance of the procedure. Moreover, the water infusion method may improve early detection of precancerous neoplasms.


To compare water infusion techniques with standard air insufflation, specifically evaluating technical quality and screening efficacy, as well as patients’ acceptance of the water infusion procedure.

Search strategy: 

We searched the Cochrane Colorectal Cancer Group Specialized Register (February 2014), the Cochrane Central Register of Controlled Trials (CENTRAL; 2014, Issue 1), Ovid MEDLINE (1950 to February 2014), Ovid EMBASE (1974 to February 2014), and ClinicalTrials.gov (1999 to February 2014) for eligible randomised controlled trials.

Selection criteria: 

We included randomised controlled trials comparing water infusion (water exchange or water immersion methods) against standard air insufflation during the insertion phase of the colonoscopy.

Data collection and analysis: 

Two review authors independently assessed the studies for inclusion and extracted data from eligible studies. We performed analysis using Review Manager software (RevMan 5).

Main results: 

We included 16 randomised controlled trials consisting of 2933 colonoscopies. Primary outcome measures were cecal intubation rate and adenoma detection; secondary outcomes were time needed to reach the cecum, pain experienced by participants during the procedure, completion of cecal intubation without sedation/analgesia, and adverse events. Completeness of colonoscopy, that is cecal intubation rate, was similar between water infusion and standard air insufflation (risk ratio 1.00, 95% confidence interval (CI) 0.97 to 1.03, P = 0.93). Adenoma detection rate, that is number of participants with at least one detected adenoma, was slightly improved with water infusion (risk ratio 1.16, 95% CI 1.04 to 1.30, P = 0.007). Assuming the fraction of patients undergoing screening colonoscopy who had one or more adenomas detected was 20 per 100 with standard colonoscopy, the use of water colonoscopy may increase the fraction to 23 per 100 individuals. From our findings, it is possible that up to 68,000 more of the 1.7 million outpatient screening colonoscopies performed annually in the United States, could detect adenomas if water infusion colonoscopy was used. In addition, with water infusion participants experienced significantly less pain (mean difference in pain score on a 0 to 10 scale: -1.57, 95% CI -2.00 to -1.14, P < 0.00001) and a significantly lower proportion of participants requested on-demand sedation or analgesia, or both (risk ratio 1.20, 95% CI 1.14 to 1.27, P < 0.00001). Qualitative analysis suggests that water infusion colonoscopy was not associated with a markedly increased rate of adverse events compared with the standard procedure.