Reply to letter: Anorectal physiology in health: A randomized trial to determine the optimum catheter for the balloon expulsion test

Abstract

We thank Chiarioni and Whitehead for their insightful comments on our recently published manuscript. 1 In their own landmark study, Chiarioni et al 2 reported the results of balloon expulsion testing (BET) using a Foley catheter in 40 healthy subjects and 286 patients with constipation. All healthy subjects expelled the Foley catheter in under 120 seconds, and this was highly reproducible on two separate testing days. By way of contrast, in our study, 25% of healthy subjects could not expel the Foley catheter within this time frame. This is in spite of (a) the older average age of our cohort (56 vs 38 years), where age has been shown previously to be inversely related to balloon expulsion time, 3 (b) the very thorough screening we performed to define healthy subjects, (c) the great care taken to replicate the methods used by Chiarioni et al, (d) the very short (<20 seconds) balloon expulsion time with other balloon catheters in almost all of our subjects, in line with recent publications 4 , and (e) the lack of other anorectal physiology differences, such as the prevalence of inadequate rectal pressure on push maneuver, between subjects who expelled the Foley catheter and those who did not.In their letter, Chiarioni and Whitehead propose that factors other than the type of balloon may influence balloon expulsion time such as patient instructions, environment, and balloon consistency.We agree with this statement; however, we used the patients as their own controls, each expelling the three different balloons in randomized order, with the same instructions, same nurse, and same test environment (private toilet). We believe that balloon consistency or deformability is the most notable difference between the catheters, and we demonstrated a very high intra-balloon pressure upon inflation of the Foley catheter balloon. Our observation is that a Foley catheter produces a very firm Bristol type 1 like balloon whereas both a party balloon and the commercial balloon have a more Bristol type 4 consistency. This, in turn, may be due to overinflation of the Foley catheter balloon, as this technique requires the Foley catheter to be filled with 50 mL of water, which is over the manufacturer-recommended limit of 30 mL. Reasons for the differing results between our study and that of Chiarioni et al may include effects due to gender, ethnicity, or cultural differences. Some of the subjects reported by Chiarioni et al were male, and all were of Italian descent, whereas our study included only females, and 86% were Caucasians, mainly first-or second-generation Australian.Our study highlights the importance of using methodology-specific normal values for BET, and we agree that replicating these data in other centers is of importance. However, as mentioned above, the off-label use of the Foley catheter with 50 mls of water might limit the further use of this specific BET protocol. O RCI D Yoav Mazor