R91 ICD-10-CM Code: Abnormal findings on diagnostic imaging of lung

R91 is the ICD-10-CM diagnosis code for abnormal findings on diagnostic imaging of lung. R91 sits in the ICD-10-CM chapter for symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (r00-r99), within the section covering abnormal findings on diagnostic imaging and in function studies, without diagnosis (r90-r94).

Header codes like R91 cannot be reported on claims directly, they organize child codes that share clinical context but the actual diagnosis must be coded to the highest level of specificity supported by the documentation. Coders should look at R91's child codes and select the one that matches the patient's documented presentation, since payers reject header codes submitted as the primary diagnosis. For risk adjustment workflows, header codes never contribute to a Medicare Advantage member's RAF score on their own; only billable child codes that happen to map to a payment HCC affect risk-adjusted plan payments.