Caustic Ingestions

Excerpt

The upper digestive tract is the primary site of tissue damage due to caustic ingestion. This part of the gut runs from the head, neck, mediastinum, and epigastric area. The oral region, pharynx, esophagus, stomach, and duodenum comprise the upper gastrointestinal tract (see Image. Digestive and Respiratory Anatomical Structures Connected to the Esophagus).

The oral region (mouth) is the entryway to the digestive system, composed of the oral cavity, gingivae, teeth, tongue, palate, and palatine tonsil area. Mechanical and some enzymatic food digestion take place in the oral cavity. Nonkeratinized stratified squamous epithelium lines most oral mucosal surfaces. Masticatory areas like the gingivae and hard palate have keratinized or parakeratinized stratified squamous epithelium.[69] Mastication muscles surround the oral region.

The pharynx passes from the cranial base to the C6 vertebra level. This upper gut area is divided into the nasopharynx, oropharynx, and laryngopharynx. The nasopharynx and oropharynx have sensory functions during eating. The oropharynx and laryngopharynx help in the transit of food boluses from the oral cavity to the esophagus.

Head and neck structures surrounding the pharynx include the upper respiratory tract, salivary glands, thyroid and parathyroid glands, vagus nerve and its branches, cervical nerves, carotid arteries and its branches, external and internal jugular veins, deglutition muscles, and lymph nodes. Nonkeratinized stratified squamous epithelium lines the pharyngeal mucosal surfaces.

The esophagus is a long muscular tube where food passes from the mouth and pharynx to the stomach. This part of the gut has cervical, thoracic, and abdominal regions. In the neck, the esophagus lies posterior to the larynx and trachea. The thoracic esophagus runs in the mediastinum anterior to the vertebral column, posterior to the trachea, and to the right of the aorta. The abdominal esophagus begins at the T11 vertebral level, where the muscular tube opens to the stomach.

The following are the 3 esophageal constrictions:

1. Cervical constriction: located 15 cm from the incisors and formed by the cricopharyngeus muscle; also known as the upper esophageal sphincter (UES)

2. Broncho-aortic constriction: a compound constriction; the aortic arch crosses the esophagus 22.5 cm from the incisors, while the left main bronchus crosses the tube 27.5 cm from the incisors

3. Diaphragmatic constriction: located 40 cm from the incisors; the area passing through the esophageal hiatus of the diaphragm, also known as the lower esophageal sphincter (LES)

These constrictions are important landmarks during esophagogastroduodenoscopy (EGD) and radiologic evaluation of esophageal lesions.

The esophageal mucosa is lined by nonkeratinized stratified squamous epithelium. The upper third of the esophagus has striated muscles. The lower third has smooth muscles. The middle third has mixed striated and smooth muscles. The esophagus has no serosa, so infections and tumors can quickly spread from this muscular tube to the neighboring regions.

The structures surrounding the esophagus include the following:

1. In the neck: trachea, aortic and carotid artery branches, vagal and cervical nerve branches, thyroid and parathyroid glands, and thoracic duct

2. In the trunk: thoracic duct, trachea, main bronchi, heart, the great blood vessels, pericardium, vagus nerve and branches, esophageal plexus, and azygos vein

3. In the abdomen: posterior aspect of the liver, vagus nerve, esophageal plexus, diaphragm, abdominal aorta and branches, stomach fundus

The stomach starts at the esophagogastric junction (EGJ), where the mucosal lining transitions from squamous to simple columnar epithelium. Gastric secretions, characterized by high acidity, serve dual roles as digestive agents and potent defense mechanisms against pathogens due to their antimicrobial properties. The mucus protects the stomach from its secretions.

The duodenum is the proximal part of the small intestine, neutralizing acidic chyme and accomplishing most of the digestive process. Bicarbonate secretions raise the duodenal pH. This part of the upper gastrointestinal tract has microvilli and simple columnar epithelium, as it is specialized for food digestion and absorption.

Caustic ingestions can injure any part of the upper digestive tract. The esophagus is most vulnerable to alkaline damage, while the stomach is most prone to acidic injury. Severe cases can cause overspills or gut perforation that can spread the damage to neighboring structures.

Caustic ingestions are severe causes of morbidity and mortality and can affect all age groups. About 80% of caustic ingestion cases in the United States occur in children. For the best outcomes, critical ingestions require coordination between surgical and medical teams.[1]