2026 ICD-10-CM Diagnosis Code N21.0Calculus in bladder

ICD-10-CM Codes›N00–N99›N20-N23›N21

ICD-10-CM N21.0
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

N21.0 is a billable ICD-10-CM diagnosis code for calculus in bladder. 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. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Calculus of urinary tract.

Code Identity

ICD-10-CM Code
N21.0
Billable Status
Yes — Valid for Submission
Code Describes
Calculus in bladder
Short Description
Calculus in bladder
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 CodeN21.0Calculus in bladder

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Calcium oxalate calculus of urinary bladder
  • Calcium oxalate urolithiasis
  • Calculus in diverticulum of urinary bladder
  • Calculus of lower urinary tract
  • Oxalate urinary bladder stone
  • Phosphate calculus of urinary bladder
  • Small calculus particles in urinary bladder
  • Uric acid calculus of urinary bladder
  • Uric acid urolithiasis
  • Urinary bladder stone

Tabular List NotesGuidance

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

Inclusion Terms

  • Calculus in diverticulum of bladder
  • Urinary bladder stone

Type 2 Excludes

  • staghorn calculus N20.0

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
      • bladder (encysted) (impacted) (urinary) (diverticulum)
    • Calculus, calculi, calculous
      • cystic
    • Calculus, calculi, calculous
      • diverticulum
        • bladder
    • Calculus, calculi, calculous
      • vesical (impacted)
    • Cystitis(exudative) (hemorrhagic) (septic) (suppurative)
      • calculous
    • Cystolithiasis
    • Stone(s)
      • bladder (diverticulum)
    • Stone(s)
      • urinary (duct) (impacted) (passage)
        • bladder (diverticulum)

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

Clinical InformationClinical

  • Calcium Oxalate Urolithiasis

    urolithiasis in which the composition of the stones is predominantly calcium oxalate.

  • Uric Acid Urolithiasis

    urolithiasis in which the composition of the stones is predominantly urate.

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 N21.0 to ICD-9-CMHistory

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

ICD-9-CM
594.0 Blad diverticulum calcul
Approximate The match is approximate rather than exact.
ICD-9-CM
594.1 Bladder calculus NEC
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 N21.0Overview

Is N21.0 (Calculus of lower urinary tract) a billable code?

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

What MS-DRG does N21.0 group to?

When calculus in bladder 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 N21.0?

Under the General Equivalence Mappings, calculus in bladder converts to ICD-9-CM 594.0 (blad diverticulum calcul) and 594.1 (bladder calculus NEC). 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.