What are the A ring and V ring in the esophagus?

Esophageal A Ring and V Ring: Anatomic Structures at the Gastroesophageal Junction

Definitions and Anatomic Location

The A ring (also called the muscular ring) is located at the junction of the tubular esophagus and esophageal vestibule, representing a muscular contraction at the proximal border of the lower esophageal sphincter. 1

The V ring (also known as the vestibular ring or Schatzki ring) is an annular constriction at the gastroesophageal mucosal junction, covered proximally by squamous epithelium and distally by gastric mucosa. 2

Key Distinguishing Features

A Ring Characteristics

• Located more proximally at the junction between tubular esophagus and esophageal vestibule 1
• Represents a muscular structure rather than a mucosal abnormality 1
• Appreciated on only approximately 5% of videofluoroscopic esophagrams 1
• Associated with severe gastroesophageal reflux disease - patients with A rings have significantly higher DeMeester pH scores (48.9 vs 15.4, p=0.033) and greater prevalence of erosive esophagitis (70% vs 10%, p=0.019) 1
• May represent either a compensatory mechanism to protect against reflux or an inflammatory consequence of peptic esophagitis 1

V Ring (Schatzki Ring) Characteristics

• Located at the gastroesophageal mucosal junction (squamocolumnar junction) 2
• Represents a submucosal fibrotic thickening 3
• Occurs in 6-14% of barium swallow examinations 2
• Often asymptomatic unless diameter ≤13 mm - "Schatzki's rule" states dysphagia is usual with ring diameters ≤13 mm, rarely occurs if diameter exceeds 20 mm 2
• Common cause of intermittent dysphagia for solids and food bolus obstruction 2, 4

Clinical Significance and Diagnostic Approach

Detection Methods

• Biphasic esophagram is superior to endoscopy for detecting lower esophageal rings, with 95% detection rate compared to 76% for endoscopy 5, 6
• Prone single-contrast views with continuous drinking of low-density barium are 2-3 times more likely to detect lower esophageal rings than upright double-contrast views due to better distal esophageal distention 5, 6
• Schatzki rings may not be visible during endoscopy unless the gastroesophageal junction is adequately distended by air insufflation 2

Important Differential Diagnosis

When encountering esophageal rings, exclude eosinophilic esophagitis by obtaining distal, mid, and proximal esophageal biopsies, as this condition can present with circular rings (transient or fixed) that may mimic Schatzki rings 5, 2

Lymphocytic esophagitis should also be considered, as it presents with rings, esophagitis, and strictures in approximately 70-75% of cases 7, 8

Common Pitfalls

• Do not assume all esophageal rings are Schatzki rings - multiple conditions including eosinophilic esophagitis and lymphocytic esophagitis can present with ring-like appearances 5, 8
• Endoscopy alone may miss lower esophageal rings - if clinical suspicion is high but endoscopy is negative, proceed with biphasic esophagram 5, 6
• A rings are frequently overlooked as they appear on only 5% of esophagrams and may be mistaken for transient contractions 1