2026 ICD-10-CM Diagnosis Code N21.9Calculus of lower urinary tract, unspecified

ICD-10-CM Codes›N00–N99›N20-N23›N21

ICD-10-CM N21.9
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

N21.9 is a billable ICD-10-CM diagnosis code for calculus of lower urinary tract, unspecified. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 693 through 694. Coders also document this condition as calculus of lower urinary tract. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Calculus of urinary tract.

Code Identity

ICD-10-CM Code
N21.9
Billable Status
Yes — Valid for Submission
Code Describes
Calculus of lower urinary tract, unspecified
Short Description
Calculus of lower urinary tract, unspecified
Same as the full description in the CMS dataset.
Parent Code
N21
Calculus of lower urinary tract

Code Classification

ChapterN00–N99Diseases of the genitourinary system
SectionN20-N23Urolithiasis
CategoryN21Calculus of lower urinary tract
This CodeN21.9Calculus of lower urinary tract, unspecified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Calculus of lower urinary tract

Tabular List NotesGuidance

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

Type 1 Excludes

  • calculus of urinary tract NOS N20.9

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.

    • Calculus, calculi, calculous
      • urinary (duct) (impacted) (passage) (tract)
        • lower
    • Stone(s)
      • urinary (duct) (impacted) (passage)
        • lower tract

Clinical ClassificationClinical

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

CCSR GEN005
Calculus of urinary tract
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Bladder Diseases

The bladder is a hollow organ in your lower abdomen that stores urine. Many conditions can affect your bladder. Some common ones are:

Read the full article at MedlinePlus

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

Convert N21.9 to ICD-9-CMHistory

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

ICD-9-CM
594.9 Lower urin calcul NOS
Exact Match The mapping is direct, with no qualifiers.

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 N21.9Overview

Is N21.9 (Calculus of lower urinary tract) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report calculus of lower urinary tract, unspecified on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does N21.9 group to?

When calculus of lower urinary tract, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 693, 694, with relative weights from 0.7817 to 1.3445 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of N21.9?

Under the General Equivalence Mappings, calculus of lower urinary tract, unspecified converts to ICD-9-CM 594.9 (lower urin calcul NOS). The mapping is a direct match.

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.