Esophageal physiology and pathophysiology

The virtual esophagus: investigating esophageal functions in silico

Esophageal and gastroesophageal junction (GEJ) diseases are highly prevalent worldwide and are a significant socioeconomic burden. Recently, applications of multiscale mathematical models of the upper gastrointestinal tract have gained attention. These in silico investigations can contribute to the development of a virtual esophagus modeling framework as part of the larger GIome and Physiome initiatives. There are also other modeling investigations that have potential screening and treatment applications. These models incorporate detailed anatomical models of the esophagus and GEJ, tissue biomechanical properties and bolus transport, sensory properties, and, potentially, bioelectrical models of the neural and myogenic pathways of esophageal and GEJ functions. A next step is to improve the integration between the different components of the virtual esophagus, encoding standards, and simulation environments to perform more realistic simulations of normal and pathophysiological functions. Ultimately, the models will be validated and will provide predictive evaluations of the effects of novel endoscopic, surgical, and pharmaceutical treatment options and will facilitate the clinical translation of these treatments.

Modeling of the mechanical function of the human gastroesophageal junction using an anatomically realistic three-dimensional model

The aim of this study was to combine the anatomy and physiology of the human gastroesophageal junction (the junction between the esophagus and the stomach) into a unified computer model. A three-dimensional (3D) computer model of the gastroesophageal junction was created using cross-sectional images from a human cadaver. The governing equations of finite deformation elasticity were incorporated into the 3D model. The model was used to predict the intraluminal pressure values (pressure inside the junction) due to the muscle contraction of the gastroesophageal junction and the effects of the surrounding structures. The intraluminal pressure results obtained from the 3D model were consistent with experimental values available in the literature. The model was also used to examine the independent roles of each muscle layer (circular and longitudinal) of the gastroesophageal junction by contracting them separately. Results showed that the intraluminal pressure values predicted by the model were primarily due to the contraction of the circular muscle layer. If the circular muscle layer was quiescent, the contraction of the longitudinal muscle layer resulted in an expansion of the junction. In conclusion, the model provided reliable predictions of the intraluminal pressure values during the contraction of a normal gastroesophageal junction. The model also provided a framework to examine the role of each muscle layer during the contraction of the gastroesophageal junction.

Esophageal motility disorders in the morbidly obese population

BACKGROUND

Most studies investigating esophageal motility among the morbidly obese have focused on the relationship between lower esophageal sphincter (LES) pressure and gastroesophageal reflux disease (GERD). Very few studies in the literature have examined motility disorders among the morbidly obese population in general outside the context of GERD. This study aimed to determine the prevalence of esophageal motility disorders in obese patients selected for bariatric surgery.

METHODS

A total of 116 obese patients (81 women and 35 men) selected for laparoscopic gastric banding underwent manometric evaluation of their esophagus from January to March 2003. Tracings were retrospectively reviewed for the end points of LES resting pressure, LES relaxation, and esophageal peristalsis.

RESULTS

The study patients had a body mass index (BMI) of 42.9 kg/m2, and a mean age of 48.6 years. The following abnormal manometric findings were demonstrated in 41% of the patients: nonspecific esophageal motility disorders (23%), nutcracker esophagus (peristaltic amplitude >180 mmHg) (11%), isolated hypertensive LES pressure (>35 mmHg) (3%), isolated hypotensive LES pressure (<12 mmHg) (3%), diffuse esophageal spasm (1%), and achalasia (1%). Only one patient with abnormal esophageal motility reported noncardiac chest pain.

CONCLUSIONS

Despite a high prevalence of esophageal dysmotility in our morbidly obese study population, there was a conspicuous absence of symptoms. Although the patients in this study were not directly questioned with regard to esophageal symptoms, several studies in the literature support our conclusion.

Two cases of steakhouse syndrome associated with nutcracker esophagus

The most common type of esophageal food-related foreign body is the meat bolus, which is frequently associated with underlying esophageal stenosis. Herein, we report two cases of meat bolus impaction associated with nutcracker esophagus. In the first case, the 63-year-old male patient had chest discomfort and swallowing difficulty after ingestion of butcher's meat. In the second case, the 55-year-old male patient had complained of swallowing difficulty after ingestion of chicken. In both cases, no pathologic findings were observed endoscopically after removal of the esophageal meat bolus. We performed esophageal manometry, which showed very high amplitudes of esophageal pressure in the mid- and distal esophagus. These findings were consistent with nutcracker esophagus. These cases show that esophageal motility disorder may be the cause of esophageal foreign body impaction, and esophageal manometry should be performed for evaluation of the cause of foreign body, especially in an endoscopically normal patient.

Secondary achalasia due to a mesenchymal tumour of the oesophagus

A rare case of a secondary achalasia or pseudoachalasia due to a mesenchymal tumour of the oesophagus is presented. A 67-year-old Caucasian man had symptoms including dysphagia, odynophagia, and weight loss for 8 months. Radiological examination revealed no signs of neoplasia but an exploratory laparotomy revealed the presence of a mesenchymal tumour of the oesophagus. Tucker's criteria constitute an important tool in the differential diagnosis of secondary achalasia from primary achalasia with clinical value, but in this case, exploratory laparotomy rather than non-invasive diagnostic procedures provided the final and definite diagnosis.

Gastric myoelectrical and antroduodenal motor activity in patients with achalasia

Achalasia is a primary motor disorder of the oesophagus, in which the myenteric plexus is involved. However, abnormalities in other parts of the digestive tract have also been described in achalasia. Whether gastric myoelectrical and duodenal motor activity in these patients is also affected is unknown. Therefore, interdigestive and postprandial gastric myoelectrical and antroduodenal motor activity were studied in 11 patients with achalasia, using electrogastrography (EGG) and stationary antroduodenal manometry. Electrogastrographically, no differences were found in the gastric frequency, incidence of dysrhythmias and postprandial/fasting power ratio. In the interdigestive state a lower propagation velocity of phase III episodes was found in the achalasia patients, but other parameters were unaltered. Postprandially, no differences were found in the number of pressure waves, in the amplitude of pressure waves or in antroduodenal coordination. We conclude that gastric myoelectrical activity and antral motor activity in patients with achalasia is normal, suggesting an intact extrinsic and intrinsic neural innervation of the distal stomach. Although postprandial duodenal motility is normal, a lower propagation velocity of phase III suggests involvement of the small intestine in achalasia.

Esophageal emergencies

Esophageal disorders are commonly seen in the emergency department. Dysphagia (difficulty swallowing) should always be taken seriously and should never be considered a functional complaint, whereas odynophagia (painful swallowing) is usually caused by an inflammatory process. This article addresses dysphagia/odynophagia, as well as esophagitis, neoplasms, gastroesophageal reflux disease, esophageal trauma, and the often difficult differentiation of chest pain of esophageal origin.

Neuro-muscular junctions of longitudinal and circular muscle fibers of the guinea-pig esophagus and their relation to myenteric plexus

The structure of the neuromuscular junctions (NMJs) and their relation to the myenteric plexus were studied by zinc iodide-osmic acid (ZIO) staining and by scanning electron microscopy in the guinea-pig esophagus. The esophageal muscle coat consisted of the inner circular and outer longitudinal striated muscle fibers. The myenteric plexus was located between the two muscle layers along its whole length and was characterized by a loose and irregular network. It was demonstrated that unmyelinated nerve fibers form NMJs with the muscle fibers of both layers. The NMJs in the longitudinal muscle can be classified as 'plate' type, whereas those of the circular muscle resemble the 'grape' type. The different NMJs in the two muscle layers probably correspond to different contractile properties. The whole-mount preparations with ZIO staining also demonstrated that some NMJs receive minute branches from the myenteric plexus. Therefore, it is likely that the myenteric plexus is involved in the control of striated muscles of the guinea-pig esophagus.