N21.1 Calculus in urethra

The ICD-10-CM code for Calculus in urethra is N21.1 (FY2026). It is a billable, claim-ready diagnosis code.

Classification

Chapter

14: Diseases of the genitourinary system (N00-N99)

Section

N20-N23: Urolithiasis (N20-N23)

Category N21

5 codes (4 billable)

FY2026 Status

Stable since FY2024

Also Known As

ICD-10-CM Alphabetic Index entries that lead to N21.1:

• Urethrolithiasis (with colic or infection)
• Urethritis (anterior) (posterior) › calculous
• Stone (s) › urethra (impacted)
• Calculus, calculi, calculous › urethra (impacted)
• Colic (bilious) (infantile) (intestinal) (recurrent) (spasmodic) › urethral › due to calculus

U.S. Hospital Utilization

• An estimated 1,810 U.S. inpatient stays in 2023 included N21.1 among the documented diagnoses.
• 160 stays listed it as the principal diagnosis.

Source: National Inpatient Sample (NIS), Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality, 2016–2023. National survey-weighted estimates.

Official Coding Guidelines

CKD staging and code assignment (N18.-)

The ICD-10-CM classifies CKD based on severity. The severity of CKD is designated by stages 1-5. Stage 2, code N18.2, equates to mild CKD; stage 3, codes N18.30-N18.32, equate to moderate CKD; and stage 4, code N18.4, equates to severe CKD. Code N18.6, End stage renal disease (ESRD), is assigned when the provider has documented end- stage renal disease (ESRD).

CKD stage plus ESRD: assign N18.6 only

If both a stage of CKD and ESRD are documented, assign code N18.6 only.

Source: CMS — ICD-10-CM Official Guidelines for Coding and Reporting, FY2026

References

• CMS — ICD-10-CM Official Code Set and Guidelines, FY2026
• CDC/NCHS — ICD-10-CM Files and Browser Tool
• AHRQ — HCUP National Inpatient Sample, Frequencies by Diagnosis Code (2016–2023)