I12.9 vs N18.4

Summary

What is different?

The conditions named and chapter.I12.9 is “Hypertensive chronic kidney disease with stage 1 through stage 4 chronic kidney disease, or unspecified chronic kidney disease”; N18.4 is “Chronic kidney disease, stage 4 (severe)”. I12.9 sits in I00-I99 — Diseases of the Circulatory System (I00-I99); N18.4 in N00-N99 — Diseases of the Genitourinary System (N00-N99).

Registry fact

Can these codes be reported together?

Yes, in the order the notes give.I12.9 is listed before N18.4; the sequencing answer below quotes the instruction.

Official ruleGuide: Code First vs Use Additional Code vs Code Also

Is there an Excludes1 relationship?

None.Neither entry carries an Excludes1 note that names the other code. I12.9 carries 5 Excludes1 notes covering other codes; the side-by-side table quotes them.

Official rule

Is there an Excludes2 relationship?

None.Neither entry carries an Excludes2 note that names the other code. I12.9 carries 2 Excludes2 notes and N18.4 carries 11 Excludes2 notes covering other codes; the side-by-side table quotes them.

Official rule

Is one more specific?

Not comparable.The codes sit in different categories; specificity is only comparable within one category.

Is one a parent or header code?

No.Both are billable codes, and neither contains the other.

Registry fact

Are there sequencing instructions?

Yes.Sequence I12.9 before N18.4: N18.4 carries a Code First instruction covering I12.9 (“hypertensive chronic kidney disease (I12.-, I13.-)”); I12.9 carries a Use Additional Code instruction covering N18.4 (“code to identify the stage of chronic kidney disease (N18.1-N18.4, N18.9)”).

Official ruleGuide: Code First vs Use Additional Code vs Code Also

Are there other coding relationships?

None found.No laterality, encounter-phase, Table of Neoplasms, Table of Drugs and Chemicals, or history-versus-active-disease relationship links these codes.

MedCoder-derived

Official rule: a tabular instructional note or a section of the ICD-10-CM Official Guidelines, quoted as published. Registry fact: the codes’ own published attributes (titles, billable status, position in the hierarchy, code set). MedCoder-derived: a reading MedCoder computes from those facts; it is not itself a rule. How to read the labels

Can these codes be reported together?

Sequencing on the claim

Official guidance behind these answers

• Section I.B.7 — Multiple coding for a single condition · applies to: Code first / Use additional code

  In addition to the etiology/manifestation convention that requires two codes to fully describe a single condition that affects multiple body systems, there are other single conditions that also require more than one code. “Use additional code” notes are found in the Tabular List at codes that are not part of an etiology/manifestation pair where a secondary code is useful to fully describe a condition. The sequencing rule is the same as the etiology/manifestation pair, “use additional code” indicates that a secondary code should be added, if known. For example, for bacterial infections that are not included in chapter 1, a secondary code from category B95, Streptococcus, Staphylococcus, and Enterococcus, as the cause of diseases classified elsewhere, or B96, Other bacterial agents as the cause of diseases classified elsewhere, may be required to identify the bacterial organism causing the infection. A “use additional code” note will normally be found at the infectious disease code, indicating a need for the organism code to be added as a secondary code. “Code first” notes are also under certain codes that are not specifically manifestation codes but may be due to an underlying cause. When there is a “code first” note and an underlying condition is present, the underlying condition should be sequenced first, if known. […]

  ICD-10-CM Official Guidelines FY2026

• Section I.A.13 — Etiology/manifestation convention (“code first”, “use additional code” and “in diseases classified elsewhere” notes) · applies to: Etiology/manifestation convention

  Certain conditions have both an underlying etiology and multiple body system manifestations due to the underlying etiology. For such conditions, the ICD-10-CM has a coding convention that requires the underlying condition be sequenced first, if applicable, followed by the manifestation. Wherever such a combination exists, there is a “use additional code” note at the etiology code, and a “code first” note at the manifestation code. These instructional notes indicate the proper sequencing order of the codes, etiology followed by manifestation. In most cases the manifestation codes will have in the code title, “in diseases classified elsewhere.” Codes with this title are a component of the etiology/ manifestation convention. The code title indicates that it is a manifestation code. “In diseases classified elsewhere” codes are never permitted to be used as first listed or principal diagnosis codes. They must be used in conjunction with an underlying condition code and they must be listed following the underlying condition. See category F02, Dementia in other diseases classified elsewhere, for an example of this convention. There are manifestation codes that do not have “in diseases classified elsewhere” in the title. For such codes, there is a “use additional code” note at the etiology code and a “code first” note at the manifestation code, and the rules for sequencing apply. […]

  ICD-10-CM Official Guidelines FY2026

Quoted from the ICD-10-CM Official Guidelines for Coding and Reporting in effect for the release shown. The tabular notes above are the code-level instruction; these sections are the convention that says how such a note is applied. Source document (CMS PDF) · Release and checksum

Side by side

Notes are the code’s own tabular entry, quoted as published. A note that names the other code is the one the verdict above rests on.

Real-world questions about this pair

• When hypertension and chronic kidney disease are both documented, is that I10 with an N18 code, or a code from I12?