What is an irregular Z‑line?

What is an Irregular Z-Line?

An irregular Z-line is a benign endoscopic finding where the squamocolumnar junction shows tongues of columnar epithelium shorter than 1 cm with no confluent columnar-lined segment—it should NOT be diagnosed as Barrett's esophagus and generally does not require routine biopsies or surveillance. 1

Endoscopic Definition and Identification

The irregular Z-line represents the transition point between esophageal squamous epithelium and gastric columnar epithelium that appears irregular rather than smooth and circumferential. 1

Key distinguishing features:

• Tongues or projections of columnar epithelium extending less than 1 cm above the gastroesophageal junction (GOJ) 1
• No confluent (continuous) columnar-lined segment present 1
• The 1 cm threshold is critical—anything ≥1 cm should be evaluated as potential Barrett's esophagus using Prague C&M criteria 1, 2

Proper landmark identification is essential: 1

• The proximal limit of longitudinal gastric folds with minimal air insufflation is the most reliable marker for the GOJ (reliability coefficient 0.88) 1, 3
• The distal end of palisade vessels can also mark the GOJ but has poor reproducibility (κ = 0.14) 1, 2

Clinical Significance and Association with Reflux

The irregular Z-line is more common in patients with gastroesophageal reflux disease but has unclear malignant potential. 1

• Case-control studies show higher frequency in patients with reflux disease 1
• One study found approximately 40% of irregular Z-lines harbored intestinal metaplasia on biopsy, though the clinical significance remains uncertain 1
• More recent data from a 2024 review confirms lack of progression to high-grade dysplasia or esophageal adenocarcinoma in patients with irregular Z-line 4
• A 2010 study found specialized intestinal metaplasia in 43.5% of irregular Z-line biopsies, with male sex and hiatus hernia as predictors 5

Management Recommendations

Biopsies are generally NOT recommended for irregular Z-lines. 1

The British Society of Gastroenterology provides clear guidance:

• Routine biopsies should not be performed on irregular Z-lines without visible abnormalities 1
• If biopsies are taken based on clinical suspicion, they should be labeled as "GOJ" (gastroesophageal junction) samples, not esophageal biopsies 1
• Surveillance endoscopy is NOT recommended for irregular Z-lines, even if intestinal metaplasia is found 1, 4

Common pitfall to avoid: Patients with irregular Z-lines are frequently mislabeled as having Barrett's esophagus, leading to unnecessary surveillance, increased healthcare costs, and reduced quality of life. 4

When to Consider Biopsy

Selective biopsy may be appropriate in specific circumstances: 1

• Visible mucosal abnormalities (nodularity, ulceration, erosions) at the Z-line 4
• High clinical suspicion based on severe reflux symptoms and other risk factors 1
• Male patients with hiatus hernia (higher risk of intestinal metaplasia) 5

If uncertain whether the appearance represents an irregular Z-line versus short-segment Barrett's esophagus, an endoscopic diagnosis of Barrett's should NOT be made. 1

Distinction from Barrett's Esophagus

The critical difference is the 1 cm minimum length threshold: 1

• Irregular Z-line: Columnar tongues <1 cm, no confluent segment
• Barrett's esophagus: Columnar epithelium ≥1 cm above the GOJ (measured as "M" in Prague criteria) with histologic confirmation of intestinal metaplasia (British guidelines) or any columnar epithelium (some guidelines) 1, 2

The reliability coefficient for endoscopic recognition of Barrett's <1 cm is only 0.22, compared to 0.72 for Barrett's ≥1 cm, highlighting the difficulty and subjectivity in diagnosing very short segments. 1