2027 ICD-10-CM Diagnosis Code R91Abnormal findings on diagnostic imaging of lung

ICD-10-CM Codes›R00–R99›R90-R94›R91

ICD-10-CM R91
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

R91 is a non-billable ICD-10-CM category code for abnormal findings on diagnostic imaging of lung, so it cannot be submitted on claims. Use a more specific code from this category instead, such as R91.1 and R91.8. As a symptom code, it should not be used as a principal diagnosis once a related definitive diagnosis has been established.

Code Identity

ICD-10-CM Code
R91
Billable Status
No — Non-Billable Category
Code Describes
Abnormal findings on diagnostic imaging of lung
Short Description
Abnormal findings on diagnostic imaging of lung
Same as the full description in the CMS dataset.
Chapter
R90-R94
Abnormal findings on diagnostic imaging and in function studies, without diagnosis

Code Classification

ChapterR00–R99Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified
SectionR90-R94Abnormal findings on diagnostic imaging and in function studies, without diagnosis
CategoryR91Abnormal findings on diagnostic imaging of lung
This CodeR91Abnormal findings on diagnostic imaging of lung

Specific Coding for Abnormal findings on diagnostic imaging of lungOverview

Non-specific codes like R91 require more characters. Use one of these billable codes instead:

  • Use R91.1 for Solitary pulmonary nodule

  • Use R91.8 for Other nonspecific abnormal finding of lung field

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to R91: its own notes plus those printed at block R90-R94 and Chapter 18. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From Block R90-R94 Abnormal findings on diagnostic imaging and in function studies, without diagnosis applies to 64 codes
  • nonspecific abnormal findings on diagnostic imaging by computerized axial tomography [CAT scan]
  • nonspecific abnormal findings on diagnostic imaging by magnetic resonance imaging [MRI][NMR]
  • nonspecific abnormal findings on diagnostic imaging by positron emission tomography [PET scan]
  • nonspecific abnormal findings on diagnostic imaging by thermography
  • nonspecific abnormal findings on diagnostic imaging by ultrasound [echogram]
  • nonspecific abnormal findings on diagnostic imaging by X-ray examination

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From Block R90-R94 Abnormal findings on diagnostic imaging and in function studies, without diagnosis applies to 64 codes
  • abnormal findings on antenatal screening of mother (O28.-)
  • diagnostic abnormal findings classified elsewhere - see Alphabetical Index

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Chapter 18 (R00-R99) Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified applies to 774 codes
  • abnormal findings on antenatal screening of mother (O28.-)
  • certain conditions originating in the perinatal period (P04-P96)
  • signs and symptoms classified in the body system chapters
  • signs and symptoms of breast (N63, N64.5)

Notes

General instructions on how these codes are used.

From Chapter 18 (R00-R99) Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified applies to 774 codes
  • This chapter includes symptoms, signs, abnormal results of clinical or other investigative procedures, and ill-defined conditions regarding which no diagnosis classifiable elsewhere is recorded.
  • Signs and symptoms that point rather definitely to a given diagnosis have been assigned to a category in other chapters of the classification. In general, categories in this chapter include the less well-defined conditions and symptoms that, without the necessary study of the case to establish a final diagnosis, point perhaps equally to two or more diseases or to two or more systems of the body. Practically all categories in the chapter could be designated 'not otherwise specified', 'unknown etiology' or 'transient'. The Alphabetical Index should be consulted to determine which symptoms and signs are to be allocated here and which to other chapters. The residual subcategories, numbered .8, are generally provided for other relevant symptoms that cannot be allocated elsewhere in the classification.
  • The conditions and signs or symptoms included in categories R00-R94 consist of:
  • (a) cases for which no more specific diagnosis can be made even after all the facts bearing on the case have been investigated;
  • (b) signs or symptoms existing at the time of initial encounter that proved to be transient and whose causes could not be determined;
  • (c) provisional diagnosis in a patient who failed to return for further investigation or care;
  • (d) cases referred elsewhere for investigation or treatment before the diagnosis was made;
  • (e) cases in which a more precise diagnosis was not available for any other reason;
  • (f) certain symptoms, for which supplementary information is provided, that represent important problems in medical care in their own right.

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name R91, its category, or a range that includes it.

Excludes1 1

These codes carry an Excludes1 note naming R91: they are not reported together with it, unless the two conditions are unrelated.

  • R22 Localized swelling, mass and lump of skin and subcutaneous tissue
    abnormal findings on diagnostic imaging (R90-R93) names R90-R93, which includes this code

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About R91Overview

What is the ICD-10 code for abnormal findings on diagnostic imaging of lung?

R91 is the ICD-10-CM category for abnormal findings on diagnostic imaging of lung, but it is a non-billable header: claims need a more specific code from this category, listed on this page.

Is R91 (Abnormal findings on diagnostic imaging of lung) a billable code?

No. This is a category header that groups the codes for abnormal findings on diagnostic imaging of lung, and headers cannot be submitted on claims. Claims for abnormal findings on diagnostic imaging of lung need a more specific code from this category, such as R91.1 and R91.8.

Can R91 be a principal diagnosis?

Use it with care. This is a symptom code, so once a definitive diagnosis explaining the abnormal findings on diagnostic imaging of lung is established, that condition takes the principal position instead.

Can R91 be reported with a code from O28?

Not as a rule. The Excludes1 note at block R90-R94, which applies to R91, lists "abnormal findings on antenatal screening of mother (O28.-)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).