Question 1: What is the ideal solution to fill the G-tube balloon?

Clinicians commonly replace silicone gastrostomy tubes, or G-tubes, in the emergency department. While the kits seem to have all the needed tools for replacement, they do not have an appropriate liquid to fill the balloon. Anecdotally, we have been told that saline degrades the balloon, leading to G-tube failure, and that balloons should be filled with either distilled water or tap water. Is this true?

While not specific to G-tubes, a 1983 study by Studer and colleagues evaluated silicone Foley catheter performance with increasing concentrations of saline (0.9 percent, 2.5 percent, 5 percent, and 10 percent) and compared this to distilled water.¹ Silicone urinary catheters were filled with each concentration of saline and tested in 22º C urine for volume loss at two weeks and four weeks. Each catheter was filled with 5 mL of the respective fluid. The authors also compared the 0.9 percent and 5 percent saline at 37º C. Catheters using distilled water had an average volume of 3.8 mL and 3.3 mL remaining at two and four weeks, respectively. The volume of 0.9 percent saline was 3.9 mL and 3.4 mL, respectively. No P values or other tests of statistical significance were provided.

A prospective randomized study by Hui and colleagues evaluated 4,000 latex 14 French Foley urethral catheters using either sterile water (n=2,011) or 0.9 percent normal saline (n=1,972).² According to the authors, it is often anecdotally reported that saline prevents catheter removal because sodium crystals block the balloon channel. The investigators filled the catheters with 10 mL of fluid and stored them in 37º C water baths for four weeks. The primary endpoint of this study was “rate of deflation failure of the Foley balloon.” The mean balloon volumes in both groups were also measured. In the sterile water group, there was a 9.2 percent deflation failure rate (185 of 2,011), with an average balloon residual volume of 9.005 mL at four weeks. In the saline group, the deflation failure rate was 8.0 percent (162 of 1,972), with a mean residual balloon volume of 9.182 mL at four weeks. There was no statistical difference between the two groups (P=0.162), suggesting no difference in failure to deflate the balloon depending on the solution used.

It is important to note that these were latex urinary catheters—not silicone—and the measured endpoint may not be applicable to G-tubes, which are not routinely deflated and reinflated as a part of their typical use.

A similar randomized study by Huang and colleagues evaluated 600 latex urinary catheters using water, saline, and glycine.³ The authors used the same endpoint of “catheter deflation–failure rate” and measured the residual volume within the balloon after six weeks in an artificial urine solution. The retained balloon volumes after six weeks for water, saline, and glycine were 9.0 mL, 9.2 mL, and 9.1 mL, respectively. There were no catheter failures, and the differences were felt to be clinically insignificant.