We recently encountered a patient with severe flatulence who previously had been subjected to innumerable diagnostic tests and ineffective therapies based on the belief that his rectal gas was produced in the colon. Analysis of three flatus samples demonstrated that nitrogen (N2) was the predominant flatus gas whereas the three gases produced in the gut (CO2, H2 [hydrogen], and CH4 [methane]) comprised <16% of rectal gas. This result plus a series of other diagnostic tests clearly indicated that the patient's flatus was derived almost entirely from swallowed air. Based on this case, the present report summarizes available data on excessive flatulence and suggests a rational approach to the patient complaining of this problem. Particular emphasis is placed upon a sequential strategy consisting of: 1) a count of flatus passages to determine if the subject truly is abnormal (normal: <20 passages/day); 2) an analysis of flatus to determine if the flatus originates from swallowed air (predominantly nitrogen) or intraluminal production (predominantly CO2, H2, and CH4); and 3) treatment based upon the origin of the rectal gas.
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APPENDIX: Methodology of collection and analysis of flatus samples
Collection of sample
The sample is collected via a rectal tube. To minimize dead space the tube should be of narrow caliber (i.e., 6 mm I.D.) and about 50 cm in length. A two-way stopcock is attached to the external end of the tube. The lubricated tube is inserted approximately 7 cm into the rectum and fixed in this position with adhesive tape. An approximately 600-ml gas-impermeable bag (Quintron, Milwaukee, WI) is attached via a three-way stopcock to the stopcock on the tube. The stopcocks are turned to allow gas to pass from the rectum to the bag. Because the rectal tube contains about 14 ml of deadspace, the first several hundred ml of flatus (2–3 flatus passages) should be discarded by closing the two-way stopcock affixed to the tube and, via the free arm of the three-way stopcock, the bag is opened to the atmosphere. The bag is completely emptied via compression, the three-way stopcock is closed to the atmosphere, and the two-way stopcock is opened to the bag. Following collection of 300 to 500 ml of flatus for analysis, the bag is sealed by appropriate manipulation of the three-way stopcock.
All gases are analyzed by gas chromatography. Care must be taken to avoid contamination with atmosphere during dilution and analysis of the sample. Using a 50-ml oiled glass syringe previously rinsed with argon, a sample is removed and analyzed for O2 and N2 using a thermal conductivity detector. If the O2 concentration exceeds 5%, atmospheric contamination during the collection process is likely. H2 is determined using a reduction detector and methane via a flame ionization detector. CO2 is determined with an infrared detector.
The materials required for flatus collection and/or the performance of the gas-analysis are available from the laboratory of the communicating author of this manuscript.