A 60-year-old woman presented with an abnormal screening endoscopy result. The patient was generally asymptomatic but remembered that she had intermittent episodes of throat obstruction. She had no specific symptoms when swallowing food and denied heartburn or acid regurgitation. Upper gastrointestinal endoscopy revealed a patulous upper esophageal sphincter (UES) in the throat (Fig. 1A and B). Upon further endoscopic entry, the upper esophagus was observed through the opening (Fig. 1C). What is the most likely diagnosis?

The UES is located between the pharynx and the esophagus and serves to prevent food from refluxing and inhaled air from entering the esophagus. The UES is essential for both protective and facilitative functions of the upper digestive and respiratory systems. As food enters, the high-pressure area of the UES must also relax, opening the lumen to allow the swallowed food to pass. The intrinsic cricopharyngeus and the extrinsic suprahyoid muscles, which are mechanically connected to the UES, are most closely related to the UES [1].

The pathophysiology of patulous UES is incompletely understood, but several factors are implicated: loss of elastic tissue in the UES, possibly due to aging [2], regional radiation or surgery, neurodegenerative disorders such as amyotrophic lateral sclerosis, and idiopathic.

In the event of UES damage, a number of symptoms may manifest, including dysphagia, nasal regurgitation, and aspiration. If the UES is open, food or liquid may enter the esophagus prematurely before the swallowing reflex has begun. This may result in impaired food bolus transport, which can lead to dysphagia. Additionally, there is a possibility of food or liquid being inhaled into the airway. It is responsible for nocturnal reflux and heartburn, particularly when the patient is lying down, whereby stomach contents flow back into the pharynx. In this way, the UES protects the respiratory system from potential hazards, such as the natural function of the digestive tract and reflux of food through its autonomous opening and closing function. The case I experienced was a 60-year-old woman who came for a medical check-up. When the endoscope was inserted, a space similar to the vocal cord was found in both pyriform sinuses. When the endoscope entered that space, it was confirmed that it was the upper esophagus, and it was discovered that the UES was open. She had no specific symptoms of dysphagia. Aspiration was not observed on esophagography (Fig. 2). Case reports of patulous UES are very rare. There is a case in which an 80-year-old Turkish man came with progressive dysphagia, which was discovered through endoscopy [3]. It was recommended that physicians utilize upper gastrointestinal endoscopy to observe the UES in patients presenting with oropharyngeal dysphagia symptoms. Another case of patulous UES was observed in a patient with amyotrophic lateral sclerosis following cricopharyngotomy [4], but this case occurred after surgery and is different from the patient I experienced, who has never had head and neck surgery.

A rare case of patulous UES was experienced. In the absence of symptoms, it is nevertheless advisable to closely observe the throat including UES during endoscopy.