EXPERIMENTAL-STUDY OF ACID BURDEN AND ACUTE ESOPHAGITIS

Background The relationship of the pH of oesophageal refluxate and its pepsin content to injury of oesophageal mucosa remains unclear. A stu dy was made of the earliest morphological alterations in the oesophage al mucosa secondary to varying concentrations of hydrochloric acid wit h or without pepsin. Methods Adult cats had varying concentrations of acid with and without 1 per cent porcine pepsin infused into the oesop hagus through a paediatric feeding tube placed 5 cm above the oesophag ogastric junction at a rate of 1 ml/min for 30 min. At autopsy 24 h la ter, the oesophagus was removed intact and scored by an expanded modif ication of a previously published histopathological scoring system. Th is included estimates of the intensity and distribution of four morpho logical features: basal cell hyperplasia (BCH), intraepithelial leucoc ytes (IELs), subepithelial leucocytes and ulcers. Each of these four c ategories was scored from 0 to 4, with a maximum injury score of 16. R esults 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 signifi cant (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 op posed to a graded level of injury based on a pH scale.