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ICD-10-CM N12: Tubulo-interstitial nephritis, not specified as acute or chronic

N12 is the billable ICD-10-CM code for tubulo-interstitial nephritis, not specified as acute or chronic, in category N12 (Tubulo-interstitial nephritis, not specified as acute or chronic) of the Renal tubulo-interstitial diseases section. As a principal diagnosis it groups to MS-DRG 689 Kidney and Urinary Tract Infections with MCC, MS-DRG 690 Kidney and Urinary Tract Infections without MCC (MDC 11 MDC 11: Diseases and Disorders of the Kidney and Urinary Tract); or MS-DRG 791 Prematurity with Major Problems, MS-DRG 793 Full Term Neonate with Major Problems (MDC 15 MDC 15: Newborns and Other Neonates with Conditions Originating in Perinatal Period). As a secondary diagnosis it is a CC, excluded with 228 principal diagnoses. 2 LCD billing and coding articles list it as covered.

Compiled from CMS files by the QuickIntell RCM Editorial Team · Data effective · Method: reference methodology · Report a data correction

Data currency: ICD-10-CM code descriptions: FY2027 (effective October 1, 2026); IPPS Table 5 (MS-DRG weights): v44 FY2027 (final rule + CN3) (effective October 1, 2026); ICD-10-CM to HCC mapping: PY2027 initial ICD-10-CM mappings (dates of service 2026) (payment year 2027); Medicare Coverage Database billing and coding articles: MCD release October 8, 2026 (effective October 4, 2026). Next CMS release: FY2028 code files, effective October 1, 2027 for the ICD-10-CM code descriptions; FY2028 final rule (August 2027), effective October 1, 2027; an April 1 interim grouper update when CMS issues one for the IPPS Table 5 (MS-DRG weights); PY2028 advance notice (February 2027) and the PY2027 midyear final mapping (spring 2027) for the ICD-10-CM to HCC mapping; weekly, every Thursday for the Medicare Coverage Database billing and coding articles.

Code
N12
billable FY2027 ICD-10-CM code
Category
N12 Tubulo-interstitial nephritis, not specified as acute or chronic
Chapter
14: Diseases of the genitourinary system (N00-N99)
CC/MCC (MS-DRG v44)
CC
CMS-HCC V28
Not mapped
POA reporting
Required

Tabular list notes for N12

Inclusion terms
  • Interstitial nephritis NOS
  • Pyelitis NOS
  • Pyelonephritis NOS
Excludes1 (never coded together)
  • calculous pyelonephritis (N20.9)

MS-DRG grouping when N12 is the principal diagnosis

MS-DRG v44 groups for N12 as principal diagnosis
MDCMS-DRGs
11 MDC 11: Diseases and Disorders of the Kidney and Urinary Tract689690
15 MDC 15: Newborns and Other Neonates with Conditions Originating in Perinatal Period791793

The final group also depends on procedures, secondary diagnoses and discharge status; the MS-DRG lookup for N12 shows the full grouping logic.

CC/MCC status and inpatient edits

As a secondary diagnosis, N12 is a CC under MS-DRG v44, unless the principal diagnosis is one of the 228 codes in its exclusion list. Check N12 against a principal diagnosis.

  • Present on admission: a POA indicator is required on inpatient claims.
  • Hospital-acquired condition: HAC 06 Catheter-Associated Urinary Tract Infection (UTI).

CMS-HCC V28 risk adjustment

N12 does not map to a payment HCC in the PY2027 CMS-HCC V28 model, so on its own it does not change a Medicare Advantage risk score.

LCD billing and coding articles that list N12

2 current Medicare billing and coding articles list N12 among the diagnoses that support medical necessity for the services they cover.

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Frequently asked questions

What does ICD-10-CM N12 mean?

N12 means tubulo-interstitial nephritis, not specified as acute or chronic. The tabular list also files these terms under it: Interstitial nephritis NOS; Pyelitis NOS; Pyelonephritis NOS. It is one of 1 billable codes under N12, tubulo-interstitial nephritis, not specified as acute or chronic.

What can't be coded with N12?

Excludes1 at N12: calculous pyelonephritis (N20.9). These are never reported together with N12.

Which MS-DRG does N12 group to?

As the principal diagnosis, N12 groups to MS-DRG 689 Kidney and Urinary Tract Infections with MCC, MS-DRG 690 Kidney and Urinary Tract Infections without MCC (MDC 11 MDC 11: Diseases and Disorders of the Kidney and Urinary Tract); or MS-DRG 791 Prematurity with Major Problems, MS-DRG 793 Full Term Neonate with Major Problems (MDC 15 MDC 15: Newborns and Other Neonates with Conditions Originating in Perinatal Period) under MS-DRG v44, before procedures and secondary diagnoses are applied.

Is N12 a CC or MCC?

N12 is a CC under MS-DRG v44; 228 principal diagnoses exclude it.

Sources

Every figure on this page is taken from the CMS publications below, as released by the Centers for Medicare & Medicaid Services. Projection built 2026-10-10. Verify against the primary file before billing or contracting decisions. The reference methodology explains how each figure is computed from these files.

Disclaimer

The descriptor and notes are reproduced from the FY2027 ICD-10-CM files; MS-DRG, CC/MCC and HCC facts come from the CMS FY2027 and PY2027 tables. Code from the medical record and the ICD-10-CM Official Guidelines. Not legal, clinical or billing advice.

Found a figure that does not match the CMS file? Report a data correction with the CMS file and the value you expected; the request reaches the editorial team through the contact form.