The ICD-10 code K21.9 is used to classify gastroesophageal reflux disease (GERD) without esophagitis. This means the patient experiences symptoms of GERD, such as heartburn and regurgitation, but without visible inflammation or damage to the esophagus lining upon examination (e.g., endoscopy). Accurate coding is crucial for medical billing, insurance claims, and tracking health statistics. When documenting GERD without esophagitis, ensure the diagnosis clearly indicates the absence of esophagitis.