Skip to main content

N18.31 ICD-10-CM Code: Chronic kidney disease, stage 3a

Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.

Inpatient Payment Groups (MS-DRG)

MS-DRGs this diagnosis helps define, as principal or secondary, per the CMS ICD-10-CM/PCS MS-DRG Definitions Manual v43.0, Appendix B.

  • MS-DRG 008 — SIMULTANEOUS PANCREAS AND KIDNEY TRANSPLANT (MDC PRE)
  • MS-DRG 019 — SIMULTANEOUS PANCREAS AND KIDNEY TRANSPLANT WITH HEMODIALYSIS (MDC PRE)
  • MS-DRG 682 — RENAL FAILURE WITH MCC (MDC 11)
  • MS-DRG 683 — RENAL FAILURE WITH CC (MDC 11)
  • MS-DRG 684 — RENAL FAILURE WITHOUT CC/MCC (MDC 11)

A diagnosis appearing in a group's logic does not by itself determine the DRG assigned to a stay; the grouper uses the full claim.

Risk Adjustment (CMS-HCC)

Payment categories this diagnosis maps to under CMS-HCC V28, payment year 2026.

  • HCC 329 — Chronic Kidney Disease, Moderate (Stage 3, Except 3B)

Risk scores depend on the enrollee's full accepted diagnosis set and segment; a category mapping alone does not determine payment.

Official Registry Overview & Definition

Chronic kidney disease, stage 3a is a billable ICD-10-CM diagnosis code (N18.31).

Official Tabular Instructional Notes

Sequencing, inclusion, and exclusion notes published for N18.31 in the official ICD-10-CM tabular list.

Excludes2 — Not Included Here

Conditions not covered by this code, but which may be reported alongside it when both are present.

Code First

Underlying conditions that must be sequenced before this code.

Use Additional Code

Supplementary codes the tabular list directs you to add.

  • Use additional code, if applicable, to identify:
  • associated cachexia (E88.A)
  • kidney transplant status (Z94.0)

Indexed Clinical Terms (1)

Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code.

  • Disease, diseased, kidney (functional) (pelvis), chronic, stage 3a

Frequently Compared Codes

The official Excludes notes on N18.31 name these codes. Each comparison page covers when the two can — or must not — be reported together.

Change history

  • FY2021 — 2020-10-01
    Added to the code set
    Chronic kidney disease, stage 3a
    FY2021 changes

Verify Before Coding

  • No Medicare Code Editor or MS-DRG Definitions Manual restrictions apply to this code.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim.

Referenced by Other Codes

Clinical classification (AHRQ CCSR):GEN003 — Chronic kidney disease (default).

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Potential MS-DRG Relationships (FY2026)

Not on the CMS CC/MCC list — as a secondary diagnosis this code does not change MS-DRG severity.

Named in the grouper logic of 5 MS-DRGs: DRG 008 (MDC PRE), DRG 019 (MDC PRE), DRG 682 (MDC 11), DRG 683 (MDC 11), DRG 684 (MDC 11).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

Official ICD-10-CM tabular notes on other codes that name N18.31 or its code family.

1 Excludes1 notes: N19 (via N18.-).

2 Code First instructions across 2 chapters: D63.1 (via N18.-), I5A (via N18.-).

1 Use Additional Code instructions: I75.81 (via N18.-).

2 Code Also instructions across 2 chapters: D59.3 (via N18.-), E20.810 (via N18.-).

Contextual Map

Every relationship of N18.31 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Hierarchy

  • N00-N99 — Chapter 14: Diseases of the Genitourinary System (N00-N99) (N00-N99) [Hierarchy]
  • N17-N19 — Acute kidney failure and chronic kidney disease [Hierarchy]

Referenced by Excludes1 notes

  • N19 — Unspecified kidney failure [Excludes1](via N18.-): “chronic kidney disease (N18.-)” · check together

Referenced by Code First instructions

  • D63.1 — Anemia in chronic kidney disease [Code First](via N18.-): “underlying chronic kidney disease (CKD) (N18.-)” · check together
  • I5A — Non-ischemic myocardial injury (non-traumatic) [Code First](via N18.-): “chronic kidney disease (CKD) (N18.-)” · check together

Referenced by Use Additional Code instructions

  • I75.81 — Atheroembolism of kidney [Use Additional Code](via N18.-): “code for any associated acute kidney failure and chronic kidney disease (N17.-, N18.-)” · check together

Referenced by Code Also instructions

  • D59.3 — Hemolytic-uremic syndrome [Code Also](via N18.-): “chronic kidney disease (N18.-)” · check together
  • E20.810 — Autosomal dominant hypocalcemia [Code Also](via N18.-): “chronic kidney disease (N18.-)” · check together

Clinical classification (CCSR)

  • GEN003 — Chronic kidney disease [CCSR]

Risk adjustment (CMS-HCC)

  • HCC 329 — Chronic Kidney Disease, Moderate (Stage 3, Except 3B) [CMS-HCC]

Potential MS-DRG

  • DRG 008 — SIMULTANEOUS PANCREAS AND KIDNEY TRANSPLANT [MS-DRG]: “SIMULTANEOUS PANCREAS AND KIDNEY TRANSPLANT (MDC PRE)”
  • DRG 019 — SIMULTANEOUS PANCREAS AND KIDNEY TRANSPLANT WITH HEMODIALYSIS [MS-DRG]: “SIMULTANEOUS PANCREAS AND KIDNEY TRANSPLANT WITH HEMODIALYSIS (MDC PRE)”
  • DRG 682 — RENAL FAILURE WITH MCC [MS-DRG]: “RENAL FAILURE WITH MCC (MDC 11)”
  • DRG 683 — RENAL FAILURE WITH CC [MS-DRG]: “RENAL FAILURE WITH CC (MDC 11)”
  • DRG 684 — RENAL FAILURE WITHOUT CC/MCC [MS-DRG]: “RENAL FAILURE WITHOUT CC/MCC (MDC 11)”

MDC crossing · procedures (3727)

  • Pre-MDC[MDC crossing]: “Pre-MDC — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs.”
  • MDC 11 — Diseases and Disorders of the Kidney and Urinary Tract [MDC crossing]: “Diseases and Disorders of the Kidney and Urinary Tract — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs.”
  • 02HA0QZ — Insertion of Implantable Heart Assist System into Heart, Open Approach [Same-MDC procedure]: “Insertion of Implantable Heart Assist System into Heart, Open Approach — grouped in MDC PRE, the procedure side of this code's crossing.” · check together
  • 02HA0RZ — Insertion of Short-term External Heart Assist System into Heart, Open Approach [Same-MDC procedure]: “Insertion of Short-term External Heart Assist System into Heart, Open Approach — grouped in MDC PRE, the procedure side of this code's crossing.” · check together
  • 02HA3QZ — Insertion of Implantable Heart Assist System into Heart, Percutaneous Approach [Same-MDC procedure]: “Insertion of Implantable Heart Assist System into Heart, Percutaneous Approach — grouped in MDC PRE, the procedure side of this code's crossing.” · check together
  • 02HA4QZ — Insertion of Implantable Heart Assist System into Heart, Percutaneous Endoscopic Approach [Same-MDC procedure]: “Insertion of Implantable Heart Assist System into Heart, Percutaneous Endoscopic Approach — grouped in MDC PRE, the procedure side of this code's crossing.” · check together
  • 02RA0LZ — Replacement of Heart with Biologic and Synthetic Substitute, Autoregulated Electrohydraulic, Open Approach [Same-MDC procedure]: “Replacement of Heart with Biologic and Synthetic Substitute, Autoregulated Electrohydraulic, Open Approach — grouped in MDC PRE, the procedure side of this code's crossing.” · check together
  • and 3722 more

Index entries

  • Disease, diseased, kidney (functional) (pelvis), chronic, stage 3a[Index term]

Nearest codes (10)

  • N18 — Chronic kidney disease (CKD) [Sibling]
  • N18.1 — Chronic kidney disease, stage 1 [Sibling]
  • N18.2 — Chronic kidney disease, stage 2 (mild) [Sibling]
  • N18.3 — Chronic kidney disease, stage 3 (moderate) [Sibling]
  • N18.30 — Chronic kidney disease, stage 3 unspecified [Sibling]
  • N18.32 — Chronic kidney disease, stage 3b [Sibling]
  • N18.4 — Chronic kidney disease, stage 4 (severe) [Sibling]
  • N18.5 — Chronic kidney disease, stage 5 [Sibling]
  • and 2 more

Change history

  • FY2021 — Added to the code set [Change history]

Nearest Codes in This Family

Official ICD-10-CM classifications closest to N18.31 in its code family, with their registry titles.

  • N18 — Chronic kidney disease (CKD)
  • N18.1 — Chronic kidney disease, stage 1
  • N18.2 — Chronic kidney disease, stage 2 (mild)
  • N18.3 — Chronic kidney disease, stage 3 (moderate)
  • N18.30 — Chronic kidney disease, stage 3 unspecified
  • N18.32 — Chronic kidney disease, stage 3b
  • N18.4 — Chronic kidney disease, stage 4 (severe)
  • N18.5 — Chronic kidney disease, stage 5
  • N18.6 — End stage renal disease
  • N18.9 — Chronic kidney disease, unspecified

View all codes in the N18 family