Experimental study of acid burden and acute oesophagitis

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Abstract
Background: The relationship of the pH of oesophageal refluxate and its pepsin content to injury of oesophageal mucosa remains unclear. A study was made of the earliest morphological alterations in the oesophageal mucosa secondary to varying concentrations of hydrochloric acid with or without pepsin. Methods: Adult cats had varying concentrations of acid with and without 1 per cent porcine pepsin infused into the oesophagus through a paediatric feeding tube placed 5 cm above the oesophagogastric junction at a rate of 1 ml/min for 30 min. At autopsy 24 h later, the oesophagus was removed intact and scored by an expanded modification of a previously published histopathological scoring system. This included estimates of the intensity and distribution of four morphological features: basal cell hyperplasia (BCH), intraepithelial leucocytes (IELs), subepithelial leucocytes and ulcers. Each of these four categories was scored from 0 to 4, with a maximum injury score of 16. Results: Mean(s.e.m.) scores were as follows: pH 1, 15·0(1·0); pH 1 with pepsin, 13·3(1·4); pH 2, 15·3(0·7); pH 2 with pepsin, 11·7(1·1); pH 3, 1·8(1·6); pH 3 with pepsin, 3·7(1·9); pH 4 with or without pepsin, 0·6(0·2). Differences between pH 3 and 4 versus pH 1 and 2 were significant (P<0·05). Conclusion: Injury to the oesophagus is more dependent on the pH of refluxate than on the presence of pepsin. Peptic injury appears to occur at a critical threshold of acid burden (pH<3) as opposed to a graded level of injury based on a pH scale.