Experimental study of acid burden and acute oesophagitis

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.

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.

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).

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.