2026 ICD-10-CM Diagnosis Code N11.9Chronic tubulo-interstitial nephritis, unspecified

ICD-10-CM Codes›N00–N99›N10-N16›N11

ICD-10-CM N11.9
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

N11.9 is a billable ICD-10-CM diagnosis code for chronic tubulo-interstitial nephritis, unspecified. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 689 through 690. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Urinary tract infections.

Code Identity

ICD-10-CM Code
N11.9
Billable Status
Yes — Valid for Submission
Code Describes
Chronic tubulo-interstitial nephritis, unspecified
Short Description
Chronic tubulo-interstitial nephritis, unspecified
Same as the full description in the CMS dataset.
Parent Code
N11
Chronic tubulo-interstitial nephritis

Code Classification

ChapterN00–N99Diseases of the genitourinary system
SectionN10-N16Renal tubulo-interstitial diseases
CategoryN11Chronic tubulo-interstitial nephritis
This CodeN11.9Chronic tubulo-interstitial nephritis, unspecified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acute on chronic tubulointerstitial nephritis
  • Chronic pyelitis
  • Chronic pyelonephritis
  • Chronic pyelonephritis with medullary necrosis
  • Chronic tubulointerstitial nephritis
  • Chronic tubulo-interstitial nephritis due to connective tissue disorder
  • Chronic tubulointerstitial nephritis due to ischemia
  • Chronic tubulointerstitial nephritis due to metabolic disease
  • Chronic tubulointerstitial nephritis due to neoplastic disease
  • Chronic tubulointerstitial nephritis following renal transplantation
  • Chronic urinary tract infection
  • Idiopathic chronic tubulointerstitial nephritis
  • Ischemic nephropathy
  • Pyelitis

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Chronic interstitial nephritis NOS
  • Chronic pyelitis NOS
  • Chronic pyelonephritis NOS

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Nephritis, nephritic(albuminuric) (azotemic) (congenital) (disseminated) (epithelial) (familial) (focal) (granulomatous) (hemorrhagic) (infantile) (nonsuppurative, excretory) (uremic)
      • tubulo-interstitial (in)
        • chronic (infectious)
    • Pyelitis(congenital) (uremic)
      • with
        • contracted kidney
    • Pyelitis(congenital) (uremic)
      • chronic
    • Pyelonephritis
      • with
        • contracted kidney
    • Pyelonephritis
      • chronic
    • Pyelonephrosis(obstructive)
      • chronic

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR GEN004
Urinary tract infections
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Pyelitis

    inflammation of the kidney pelvis and kidney calices where urine is collected before discharge, but does not involve the renal parenchyma (the nephrons) where urine is processed.

  • Pyelitis

    inflammation of the renal pelvis.

  • Chronic Pyelonephritis

    persistent pyelonephritis.

  • Ischemic Nephropathy

    nephropathy due to hypoperfusion of the kidney.

Patient EducationClinical

Kidney Diseases

You have two kidneys, each about the size of your fist. They are near the middle of your back, just below the rib cage. Inside each kidney there are about a million tiny structures called nephrons. They filter your blood. They remove wastes and extra water, which become urine. The urine flows through tubes called ureters.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert N11.9 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
590.80 Pyelonephritis NOS
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About N11.9Overview

Is N11.9 (Chronic tubulo-interstitial nephritis) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report chronic tubulo-interstitial nephritis, unspecified on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does N11.9 group to?

When chronic tubulo-interstitial nephritis, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 689, 690, with relative weights from 0.8095 to 1.1603 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of N11.9?

Under the General Equivalence Mappings, chronic tubulo-interstitial nephritis, unspecified converts to ICD-9-CM 590.80 (pyelonephritis NOS). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.