2026 ICD-10-CM Diagnosis Code N12Tubulo-interstitial nephritis, not specified as acute or chronic
ICD-10-CM Codes›N00–N99›N10-N16›N12
- Billable — Valid for Submission
- Not Chronic
N12 is a billable ICD-10-CM diagnosis code for tubulo-interstitial nephritis, not specified as acute or chronic. 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
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Anti-glomerular basement membrane disease
- Anti-glomerular basement membrane tubulointerstitial nephritis
- Diffuse pyelonephritis
- Familial interstitial nephritis
- Granulomatous tubulointerstitial nephritis
- Idiopathic granulomatous interstitial nephropathy
- Idiopathic interstitial tubulonephritis
- Immunologic mediated TIN
- Mycoplasmal pyelonephritis
- Primary tubulointerstitial nephritis
- Pyelitis
- Pyelonephritis
- Secondary tubulointerstitial nephritis
- Subacute pyelonephritis
- Tubulointerstitial nephritis
- Tubulointerstitial nephritis with uveitis syndrome
Tabular List NotesGuidance
Coding notes and annotation back-references applicable to this code.
Inclusion Terms
- Interstitial nephritis NOS
- Pyelitis NOS
- Pyelonephritis NOS
Type 1 Excludes
- calculous pyelonephritis N20.9
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
- Disease, diseased - See Also: Syndrome;
- antiglomerular basement membrane (anti- GBM) antibody - M31.0
- tubulo-interstitial nephritis - N12
- renal (functional) (pelvis) - See Also: Disease, kidney; - N28.9
- with
- interstitial nephritis - N12
- Nephritis, nephritic (albuminuric) (azotemic) (congenital) (disseminated) (epithelial) (familial) (focal) (granulomatous) (hemorrhagic) (infantile) (nonsuppurative, excretory) (uremic) - N05.9
- Pyelonephritis - See Also: Nephritis, tubulo-interstitial;
- nonobstructive - N12
- Pyonephritis - N12
External Cause of Injuries IndexGuidance
References for this code in the External Cause of Injuries Index.
- Disease, diseased
- antiglomerular basement membrane (anti- GBM) antibody
- tubulo-interstitial nephritis
- Disease, diseased
- renal (functional) (pelvis)
- with
- interstitial nephritis
- Nephritis, nephritic(albuminuric) (azotemic) (congenital) (disseminated) (epithelial) (familial) (focal) (granulomatous) (hemorrhagic) (infantile) (nonsuppurative, excretory) (uremic)
- antitubular basement membrane (tubulo-interstitial) NEC
- Nephritis, nephritic(albuminuric) (azotemic) (congenital) (disseminated) (epithelial) (familial) (focal) (granulomatous) (hemorrhagic) (infantile) (nonsuppurative, excretory) (uremic)
- tubulo-interstitial (in)
- Pyelonephritis
- nonobstructive
- Pyonephritis
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
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.Emphysematous Pyelonephritis
acute often necrotizing pyelonephritis characterized by accumulation of gas within and around renal parenchyma. emphysematous pyelonephritis is typically associated with bacterial infection in diabetes mellitus and immunocompromised patient.Nephritis, Hereditary
a group of inherited conditions characterized initially by hematuria and slowly progressing to renal insufficiency. the most common form is the alport syndrome (hereditary nephritis with hearing loss) which is caused by mutations in genes for type iv collagen and defective glomerular basement membrane.Pyelonephritis
inflammation of the kidney involving the renal parenchyma (the nephrons); kidney pelvis; and kidney calices. it is characterized by abdominal pain; fever; nausea; vomiting; and occasionally diarrhea.Pyelonephritis, Xanthogranulomatous
a chronic inflammatory condition of the kidney resulting in diffuse renal destruction, a grossly enlarged and nonfunctioning kidney associated with nephrolithiasis and kidney stones.Pyelitis
inflammation of the renal pelvis.
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 N12 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About N12Overview
Is N12 a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report tubulo-interstitial nephritis, not specified as acute or chronic on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does N12 group to?
When tubulo-interstitial nephritis, not specified as acute or chronic 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 N12?
Under the General Equivalence Mappings, tubulo-interstitial nephritis, not specified as acute or chronic converts to ICD-9-CM 590.80 (pyelonephritis NOS). The mapping is approximate, so confirm the match fits the documentation.
Footnotes
[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.
