N12Tubulo-interstitial nephritis, not specified as acute or chronic

N12 is the ICD-10-CM diagnosis code for tubulo-interstitial nephritis, not specified as acute or chronic. It belongs to block N10-N16 (renal tubulo-interstitial diseases) and chapter 14 (diseases of the genitourinary system). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Don't report N12 together with the conditions in its Excludes1 note: calculous pyelonephritis (N20.9).

As a secondary diagnosis it is a CC (complication or comorbidity), which can move an inpatient stay into the "with CC" MS-DRG of its family, unless the principal diagnosis excludes it.

In MS-DRG v44.0, it is part of the grouping logic for DRG 689 (Kidney and Urinary Tract Infections with MCC, relative weight 1.1415), DRG 690 (Kidney and Urinary Tract Infections without MCC, relative weight 0.801), DRG 791 (Prematurity with Major Problems, relative weight 4.1075) and DRG 793 (Full Term Neonate with Major Problems, relative weight 4.2195), in MDC 11 (Diseases and Disorders of the Kidney and Urinary Tract) and MDC 15 (Newborns and Other Neonates with Conditions Originating in the Perinatal Period), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 590.80 (pyelonephritis, unspecified).