**1. Introduction**

Eosinophilic esophagitis (EoE) represents a chronic, immune/antigen mediated disease characterized by esophageal dysfunction and eosinophilic inflammation (Liacouras et al., 2011). The past few years have witnessed a progressive rise in diagnosed cases of EoE, which has become the second most common chronic esophageal disease after gastroesophageal reflux (Lucendo, 2010). In spite of this, EoE remains underdiagnosed in many cases, especially because endoscopic findings are usually much harder to detect than those observed in esophageal growths (such as neoplasms) or erosive disorders. A great variety of endoscopic findings has been described in literature for EoE patient, including an apparently normal esophagus, which suggests that changes in this organ's appearance are not only complex, but also subtle enough to be overlooked by an endoscopist unaccustomed to diagnosing this disease.

At the same time, research efforts aimed at providing efficient therapy for this chronic illness has also intensified. Unfortunately, no treatment strategies have been commonly accepted to date, making adequate management of these patients somewhat controversial (González-Castillo et al., 2010). That being said, 3 different therapeutic approaches have been used effectively in patients with EoE. The first approach involves endoscopic dilation, a technique which is frequently able to solve alterations in the caliber of the esophagus, including a narrowing of the lumen (Schoepfer et al., 2009). From the earliest documented cases, mechanical dilation has been used as a treatment option for EoE, similar to the way it is used in other cases of fibrous esophageal stenosis, such as peptic stenosis or following caustication.

The classification of EoE as an immunoallergic disorder has led to a second approach, namely that of treating patients with drugs for bronchial asthma (Furuta & Straumann, 2006). However, because no specifically approved drugs are currently available for EoE patients, these treatment must be due out label.

 From the first studies performed on children with EoE, allergies to certain dietary components have been demonstrated to contribute significantly to its pathogenesis; indeed, it is well-documented that both the symptoms of the disease and histology levels improve after eliminating certain foods from the diet (Liacouras et al., 2005). However, while early studies based exclusively on elemental diets showed enormous efficacy in reverting EoE (Kelly et al., 1995), this approach is not plausible in adults or chronic patients.

Endoscopic Aspects of Eosinophilic Esophagitis: From Diagnosis to Therapy 65

Endoscopy with esophageal biopsy remains the only reliable diagnostic test for EoE. Consequently, in order for clinicians to recognize the disease more easily, a better awareness of the distinct endoscopic features of EoE is essential. Retrospective re-evaluations of the endoscopic appearance of the esophagus in those patients eventually diagnosed with EoE have revealed that esophageal appearance had been described as normal in between one quarter to one third of the cases (Müller et al., 2007; Sgouros et al., 2006; Liacouras et al., 2005). It is important to note, however, that even though the endoscopic findings are subtle, remarkable abnormalities can still be detected in the majority of patients, as we describe

Endoscopy has helped identify a great number of esophageal abnormalities in patients with EoE. These include fixed esophageal rings that sometimes reduce the esophageal lumen (a phenomenon known as trachealization) and transient esophageal rings (also called feline folds or felinization). Diffuse nodularity/granularity of the mucosa has also been described, along with widespread exudative mucosal lesions, either in the form of whitish papulae of varying sizes clustered together (white spots) or as large, white, exudative fibrinoid lesions. These whitish lesions on the mucosa resemble a mild, superficial Candida infection, but histopathology shows micro-abscesses made up of eosinophils (Lucendo et al., 2007). Furthermore, a loss of the common vascular pattern of the mucosa has been described (Lucendo, 2007; Straumann et al., 2004). Some of the most common findings are longitudinal furrows (referred to as "corrugated esophagus," which is an architectural analogy to a grooved column) (Straumann et al., 2004), diffuse esophageal narrowing, and esophageal lacerations induced by passage of the endoscope. Mucosal fragility, also called *crêpe-paper* mucosa (Straumann et al., 2003), is an important feature of this pathology as it may cause tears during upper endoscopy or even if the patient tries to dislodge impacted food by inducing vomiting (Lucendo et al., 2011). However, because all of these endoscopic features have been described in other esophageal disorders, none can be considered pathognomonic

To shed light on the varied endoscopic appearances of EoE, we have classified them according to two independent yet complementary aspects: alterations in the caliber of the

• Alterations in the caliber of the esophagus, which appear as a consequence of motor esophageal disturbances associated to EoE in children (Nurko et al., 2009) and adults (Moawad, 2011; Lucendo et al, 2007), or after fibrous remodeling of the organ. In this case, multiple simultaneous contraction rings may be observed; these may block the passage of the endoscope while still permitting observation of the distal lumen. Alternatively, the clinician may notice regular concentric strictures, which impede both passage of the endoscope and observation of the distal mucosa (Lucendo et al, 2007). The smaller caliber of the esophagus may go unnoticed in barium contrast radiography and endoscopy (Vasilopoulos et al., 2002). All of these changes may occur without mucosal lesions (e.g. erosions or ulcerations), unlike what happens in peptic disease. Alterations in the caliber are found predominantly in the mid and distal esophageal thirds and can be reverted with treatment; in fact, since motor disturbances can be successfully treated with topical steroid treatment, a functional rather than structural

• Alteration in the appearance of the mucosa. In a study analyzing different endoscopic findings associated with EoE in parallel with the intensity of histological lesions,

esophagus and alterations in the appearance of the mucosa (Lucendo et al., 2007).

origin of caliber alterations in EoE should be considered.

below.

for EoE.

One important stumbling block to determining the most effective treatment for EoE is the lack of studies directly comparing different treatment strategies for the disease. Such studies will be necessary before the best therapeutic option for EoE can be established.

In this chapter we review the various endoscopic lesions described in EoE to date. This should help relatively inexperienced endoscopists screen for patients suspected of having EoE. We will also discuss the effects and risks of endoscopic treatment by dilation in EoE patients by reviewing the current literature.
