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ICD-10-CM 2027 diagnosis code

N21.0Calculus in bladder

✓ Billable / specific

N21.0 is a valid, billable ICD-10-CM code for calculus in bladder. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.

Looking up by condition? See ICD-10 code for Cystolithiasis.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About N21.0

N21.0 is the ICD-10-CM diagnosis code for calculus in bladder. It belongs to category N21 (calculus of lower urinary tract), block N20-N23 (Urolithiasis) 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.

Within N21 (calculus of lower urinary tract), N21.0 is specifically for calculus in bladder. Related codes cover calculus in urethra (N21.1), other lower urinary tract calculus (N21.8) and unspecified (N21.9).

The conditions in its Excludes2 note aren't part of N21.0, but may be coded alongside it if the patient has both: staghorn calculus (N20.0).

It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.

In MS-DRG v44.0, it is part of the grouping logic for DRG 693 (Urinary Stones with MCC, relative weight 1.3168) and DRG 694 (Urinary Stones without MCC, relative weight 0.7815), in MDC 11 (Diseases and Disorders of the Kidney and Urinary Tract), 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 594.0 (calculus in diverticulum of bladder) and 594.1 (other calculus in bladder).

Coding notes

Applicable toConditions and synonyms classified to this code
  • Calculus in diverticulum of bladder
  • Urinary bladder stone
Excludes2Not included here — may be reported together if both conditions exist
  • staghorn calculus (N20.0)

Notes that apply from higher levels

Instructions written at a parent level also apply to N21.0.

› From N21 Calculus of lower urinary tract
Includes
  • calculus of lower urinary tract with cystitis and urethritis

Broader instructions also apply from Chapter 14: Diseases of the genitourinary system.

Alphabetic index entries

8 entries

Terms in the official ICD-10-CM index that lead to N21.0.

Codes whose notes reference N21.0

MS-DRG v44.0 grouping

All DRGs →

Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.

MDC 11 · Diseases and Disorders of the Kidney and Urinary Tract

ICD-9-CM equivalent

Converter →
  • 594.0Calculus in diverticulum of bladderapproximate
  • 594.1Other calculus in bladderapproximate

From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • No changes since FY2016.

Common questions about N21.0

Is N21.0 billable?

Yes. N21.0 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can N21.0 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict N21.0 as a principal diagnosis.

Is N21.0 a CC or MCC?

No. N21.0 is neither a CC nor an MCC under MS-DRG v44.0.

What DRG does N21.0 group to?

N21.0 is used in the MS-DRG v44.0 logic for MS-DRG 693 (Urinary Stones with MCC) and MS-DRG 694 (Urinary Stones without MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.

What is the ICD-9 code for N21.0?

The CMS General Equivalence Mappings map N21.0 to ICD-9-CM 594.0 and 594.1.