Eosinophilic oesophagitis versus reflux oesophagitis.

Reflux oesophagitis (RO) is defined as the inflammation of the lower oesophagus due to damage caused by acid reflux from the stomach. Histopathologic features of acid reflux include epithelial hyperplasia, baloon cells, basal cell hyperplasia, papillary elongation, dilated intercellular spaces representing epithelial oedema, vascular congestion, and inflammatory cell infiltration comprising lymphocytes, neutrophils and eosinophils, most of which are nonspecific. Eosinophils, on the other hand, are considered to be important in the differential diagnosis of RO and EoO which is a chronic inflammatory disorder characterized by eosinophil infiltration of the oesophageal mucosa associated with a history of atopy or allergy. A cut off value of more than 15 eosinophils per high power field is suggestive of EoO with a tendency of eosinophils to concentrate in the superficial parts of squamous mucosa just below the luminal surface where they tend to form eosinophilic microabsesses. Dense fibrosis is seen in up to one-third of the patients with EoO together with an increase in the number of eosinophils in the lamina propria. In patients with intermediate levels of eosinophil counts (7-15 eos/hpf) immunohistochemistry for eosinophil secretory products could prove useful as it highlights degranulated eosinophils. In conclusion, distinguishing EoO from RO requires a thorough clinical, endoscopic and histologic evaluation of the patient which can only be achieved when close communication between pathologist and gastroenterologist is established.