The report on hiatus hernia by Kahrilas et al in this issue (see page 476) represents a milestone in the investigation of the impact of hiatus hernia on the mechanics of the gastro-oesophageal junction. Casual readers will probably not appreciate this—their first reaction more likely being that there is nothing new in this report. This reaction is understandable as Kahrilaset al’s findings are what would be predicted. The study is a milestone because it has actually made real in vivo measurements in humans. These measurements give a sound foundation for studies which will undoubtedly follow in the future and which will probe how hiatus hernia influences the mechanics of individual episodes of gastro-oesophageal reflux.

The casual reader is also unlikely to appreciate fully the technical demands presented by the measurements made by Kahrilaset al which is, of course, why there has been so much theory and deduction and so little direct observation in this field. Interpretation of manometry and fluoroscopy relied on spatial referencing of …