Background and purpose

The Los Angeles (LA) classification is the most widely used endoscopic system for grading erosive esophagitis in the setting of gastroesophageal reflux disease (GERD). It does not diagnose GERD by itself; instead, it describes the severity of visible mucosal injury when erosions or ulcerations are present. The scheme was introduced to reduce ambiguous language (for example, “mild,” “moderate,” or “severe” esophagitis) and to improve reproducibility between endoscopists and across centers, including clinical trials of acid-suppressive therapy.

Over time, the definitions were refined so that key distinctions—especially the 5 mm length threshold, the concept of breaks continuous between mucosal folds, and circumferential involvement—could be applied in a more standardized way. The LA system remains an endoscopic tool: it reflects what is seen at esophagoscopy, not patient-reported symptoms, pH study results, or histology.

What the LA system grades

LA grades apply to mucosal breaks, meaning endoscopically visible defects of the esophageal mucosa (erosions or ulcerations), as opposed to erythema or edema alone. If no mucosal breaks are identified, the esophagus is not assigned an LA grade A–D within this framework, even when other reflux-related findings (such as mucosal friability or a lax hiatus) are present. That limitation is important when documenting endoscopy: absence of LA-grade erosions does not exclude pathologic reflux or symptomatic GERD, and conversely, erosive disease may be present with atypical or minimal symptoms.

When multiple breaks are seen, grading should reflect the worst or most extensive lesion—the pattern that would place the examination into the highest applicable LA category. This “worst lesion” rule aligns with how severity is communicated for treatment decisions, follow-up, and research stratification.

Definitions of the LA grades (A through D)

The grades form an ordered hierarchy from least to most extensive mucosal injury among erosive patterns included in the classification.

Grade A

Grade A esophagitis is defined by the presence of one or more mucosal breaks, each measuring 5 mm or less in extent, with none of these breaks extending continuously between the tops of two mucosal folds. In practice, endoscopists mentally “measure” against the fold geometry: small, discrete erosions that remain confined between folds or on the fold slopes without bridging from one fold crest to another fit this grade.

Grade B

Grade B is assigned when there is at least one mucosal break longer than 5 mm, again with no break that runs continuously between the tops of two mucosal folds. The key discriminator from grade A is therefore length (>5 mm for any single break), not circumferential extent across the lumen. Long linear erosions may still be grade B if they do not meet the specific “continuous between fold tops” pattern that defines grades C and D.

Grade C

Grade C reflects more extensive injury: there is at least one mucosal break that is continuous between the tops of two or more mucosal folds, meaning the break bridges the esophageal folds in a way that defines confluent mucosal loss along the axial plane of the lumen, yet the process involves less than 75% of the esophageal circumference. The circumferential cut point separates circumferential but not circumferential-dominant injury (C) from near-circumferential or circumferential confluent disease (D).

Grade D

Grade D denotes the most extensive erosive pattern in the LA system: a mucosal break that involves at least 75% of the esophageal circumference, in the setting of the same continuous between folds morphology that defines grade C. Endoscopically, this often corresponds to confluent ulceration or erosion that encircles much of the lumen and is readily appreciated as circumferential disease.

Decision logic used in the calculator

The CalcMD tool walks through the same branching rules clinicians use at the console:

• If there are no mucosal breaks, LA grades A–D are not assigned.
• If any qualifying break is continuous between mucosal fold tops, the grade is C or D based on whether circumferential involvement is below or at/above 75%.
• If no break bridges fold tops, the grade is A or B depending on whether the longest break is ≤5 mm or >5 mm.

This ordering matters because the fold-continuity pattern moves the examination into the C/D pathway, which takes precedence over the simple length-based A/B distinction.

Measurement and interpretation at endoscopy

Accurate LA grading benefits from careful inspection in a well-distended esophagus, with attention to the longitudinal and circumferential extent of each break. The 5 mm threshold is a visual anchor—often compared to the approximate width of an open biopsy forceps or similar endoscopic reference—rather than a micrometer-level measurement. When multiple discrete erosions are present, identify the single worst break that drives the grade.

The phrase continuous between the tops of mucosal folds is a specific morphologic pattern. Superficial erythema, friability, or pinpoint bleeding without a true mucosal break does not create an LA grade. Likewise, other etiologies of esophagitis (infectious, pill-induced, eosinophilic, etc.) may produce breaks that resemble reflux injury; LA grading can still describe the endoscopic appearance of mucosal breaks, but clinical interpretation should integrate history, biopsies, and differential diagnosis.

Relationship to symptoms, complications, and follow-up

LA grade correlates imperfectly with symptoms: some patients with high-grade erosive disease have modest heartburn, while others with severe symptoms have no mucosal breaks. Endoscopic grade nevertheless carries prognostic and management implications in many settings: higher grades are associated with greater mucosal injury burden and, in some cohorts, with higher risk of complications such as stricture or bleeding, and with greater expected benefit from potent acid suppression and appropriate follow-up. Repeat endoscopy may be considered after a course of therapy to document mucosal healing, particularly when initial findings were severe, symptoms persist despite treatment, or alarm features are present—exact indications depend on guideline-based, patient-specific judgment.

LA grading is orthogonal to Barrett esophagus detection: specialized inspection for columnar-lined esophagus and targeted biopsies follow separate protocols. A normal LA grade does not rule out Barrett, and erosive disease does not replace the need for biopsy when intestinal metaplasia or dysplasia is suspected.

Research, quality assurance, and documentation

Because LA grades are used as stratification variables in studies of GERD therapies, consistent application improves comparability between trials. In quality improvement, photodocumentation and periodic calibration among endoscopists can reduce drift in how “continuous between folds” and circumferential percentages are judged. In the medical record, pairing the LA letter grade with a short text description of the worst break (length, fold involvement, and estimated circumference) often communicates more than the letter alone and supports accurate coding and handoffs.