Crystal's MCW Coder HubICD-10-CM: N18.4 - Chronic Kidney Disease, Stage 4 (Severe)
Code Description
N18.4 is a billable/specific ICD-10-CM diagnosis code used to identify Chronic Kidney Disease, Stage 4 (Severe) for reimbursement and clinical documentation purposes. This code became effective October 1, 2015, and remains active for the fiscal year October 1, 2025 through September 30, 2026.
Clinical Definition
Chronic Kidney Disease Stage 4 represents severe kidney damage with significantly reduced kidney function. At this stage, the glomerular filtration rate (GFR) ranges from 15-29 mL/min/1.73m². The kidneys are severely damaged and approaching kidney failure, requiring close monitoring and preparation for potential renal replacement therapy.
Code Hierarchy & Tree Structure
ICD-10-CM Code Tree for [[N18.4]]
Chapter 14: Diseases of the Genitourinary System (N00-N99)
└── Acute Kidney Failure and Chronic Kidney Disease (N17-N19)
└── Chronic Kidney Disease (N18)
├── 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
│ ├── N18.31 - Chronic kidney disease, stage 3a
│ └── N18.32 - Chronic kidney disease, stage 3b
├── N18.4 - Chronic kidney disease, stage 4 (severe) ← THIS CODE
├── N18.5 - Chronic kidney disease, stage 5
├── N18.6 - End stage renal disease
└── N18.9 - Chronic kidney disease, unspecified
Parent Code: N18 - Chronic kidney disease (CKD)
Adjacent Codes:
Official Coding Guidelines
Code First Requirements
When coding N18.4, the following conditions must be coded FIRST if documented:
| Condition | ICD-10-CM Code |
|---|---|
| Diabetic chronic kidney disease | E08.22, E09.22, E10.22, E11.22, E13.22 |
| Hypertensive chronic kidney disease | I12.-, I13.- |
Use Additional Code Requirements
The following codes should be added when applicable:
| Condition | ICD-10-CM Code |
|---|---|
| Associated cachexia | E88.A |
| Kidney transplant status | Z94.0 |
| Stage of CKD (when coding hypertensive CKD) | N18.1-N18.4, N18.9 |
Important Coding Notes
- Always code the stage of CKD when documented by the provider
- Do not code CKD stage based solely on GFR results without provider documentation
- If both CKD stage and ESRD are documented, assign code N18.6 only
- CKD Stage 4 with dialysis dependence should be coded as N18.6 (ESRD), not N18.4
Includes & Excludes
Type 1 Excludes (Never Code Together)
| Code | Description |
|---|---|
| N18.6 | End stage renal disease (if patient requires chronic dialysis) |
| N18.5 | Chronic kidney disease, stage 5 |
Type 2 Excludes (May Code Together If Clinically Appropriate)
| Code Range | Description |
|---|---|
| P04-P96 | Certain conditions originating in the perinatal period |
| A00-B99 | Certain infectious and parasitic diseases |
| O00-O9A | Complications of pregnancy, childbirth and the puerperium |
| Q00-Q99 | Congenital malformations, deformations and chromosomal abnormalities |
| E00-E88 | Endocrine, nutritional and metabolic diseases |
| S00-T88 | Injury, poisoning and certain other consequences of external causes |
| C00-D49 | Neoplasms |
| R00-R94 | Symptoms, signs and abnormal clinical and laboratory findings |
Category-Level Excludes (N17-N19)
| Code | Description |
|---|---|
| P96.0 | Congenital renal failure |
| N14.- | Drug- and heavy-metal-induced tubulo-interstitial and tubular conditions |
| R39.2 | Extrarenal uremia / Prerenal uremia |
| D59.3- | Hemolytic-uremic syndrome |
| K76.7 | Hepatorenal syndrome |
| O90.41 | Postpartum hepatorenal syndrome / Renal failure following labor and delivery |
| T79.5 | Posttraumatic renal failure |
| O00-O07, O08.4 | Renal failure complicating abortion or ectopic or molar pregnancy |
| N99.0 | Renal failure postprocedural |
HCC Risk Adjustment Information (2026 CMS-HCC V28)
Hierarchical Condition Category Mapping
| Attribute | Value |
|---|---|
| HCC Model | CMS-HCC Version 28 (V28) |
| HCC Category | HCC 138 |
| HCC Description | Chronic Kidney Disease, Stage 4 |
| Risk Score Impact | Moderate-High |
| Model Year | 2026 (Full V28 Implementation) |
V28 Model Changes (2026)
The CMS-HCC Model V28 fully implemented in 2026 includes 115 HCC categories to better stratify conditions by severity. Key changes affecting N18.4:
- More granular CKD staging compared to V24 model
- Higher risk scores for documented Stage 4 CKD vs. unspecified CKD
- Requires annual recapture for Medicare Advantage risk adjustment
- eGFR documentation strongly recommended to support stage assignment
HCC Coding Best Practices
- Document eGFR values to support CKD stage assignment
- Capture CKD stage annually for risk adjustment purposes
- Link CKD to underlying etiology (diabetes, hypertension, etc.)
- Avoid unspecified CKD (N18.9) when stage is known
MS-DRG Mapping (Inpatient)
Primary MS-DRG Assignments
N18.4 maps to the following Medicare Severity Diagnosis-Related Groups for fiscal year 2026 (MS-DRG V43.0):
| MS-DRG | Description | MDC | Relative Weight | CC/MCC Status |
|---|---|---|---|---|
| 682 | Renal Failure with MCC | 11 | 1.4810 | Major Complication/Comorbidity |
| 683 | Renal Failure with CC | 11 | 0.8758 | Complication/Comorbidity |
| 684 | Renal Failure without CC/MCC | 11 | 0.6003 | No CC/MCC |
Additional MS-DRG Mappings
| MS-DRG | Description |
|---|---|
| 008 | Simultaneous pancreas and kidney transplant |
| 019 | Simultaneous pancreas and kidney transplant with hemodialysis |
MDC Information
- MDC 11: Diseases & Disorders of the Kidney & Urinary Tract
- Relative Weight Range: 0.6003 - 1.4810 (depending on CC/MCC presence)
- Geometric Mean Length of Stay: Varies by facility and patient acuity
CC/MCC Designation
- N18.4 is classified as a CC (Complication/Comorbidity)
- When paired with other qualifying conditions, may contribute to MCC assignment
- CC status affects hospital reimbursement under IPPS
Related CPT Codes & wRVU Information
Evaluation & Management (E/M) Codes
| CPT Code | Description | Setting | wRVU (2026) | Assistant Payable |
|---|---|---|---|---|
| 99202 | Office/outpatient E/M, new patient, low complexity | Office | 0.70 | No |
| 99203 | Office/outpatient E/M, new patient, moderate complexity | Office | 1.30 | No |
| 99204 | Office/outpatient E/M, new patient, high complexity | Office | 1.92 | No |
| 99205 | Office/outpatient E/M, new patient, high complexity | Office | 2.74 | No |
| 99212 | Office/outpatient E/M, established patient, low complexity | Office | 0.48 | No |
| 99213 | Office/outpatient E/M, established patient, moderate complexity | Office | 0.88 | No |
| 99214 | Office/outpatient E/M, established patient, high complexity | Office | 1.36 | No |
| 99215 | Office/outpatient E/M, established patient, high complexity | Office | 1.92 | No |
| 99221 | Initial hospital care, low complexity | Inpatient | 1.42 | Yes |
| 99222 | Initial hospital care, moderate complexity | Inpatient | 2.11 | Yes |
| 99223 | Initial hospital care, high complexity | Inpatient | 3.00 | Yes |
| 99231 | Subsequent hospital care, low complexity | Inpatient | 0.74 | Yes |
| 99232 | Subsequent hospital care, moderate complexity | Inpatient | 1.26 | Yes |
| 99233 | Subsequent hospital care, high complexity | Inpatient | 1.88 | Yes |
| 99238 | Hospital discharge day management, ≤30 min | Inpatient | 0.81 | No |
| 99239 | Hospital discharge day management, >30 min | Inpatient | 1.28 | No |
Nephrology-Specific CPT Codes
| CPT Code | Description | wRVU (2026) | Assistant Payable |
|---|---|---|---|
| 90951 | ESRD services, patient <2 years, 4+ face-to-face visits/month | 3.58 | No |
| 90952 | ESRD services, patient 2-11 years, 4+ face-to-face visits/month | 3.26 | No |
| 90953 | ESRD services, patient 12-19 years, 4+ face-to-face visits/month | 2.94 | No |
| 90954 | ESRD services, patient 20+ years, 4+ face-to-face visits/month | 2.67 | No |
| 90955 | ESRD services, patient <2 years, 2-3 face-to-face visits/month | 2.39 | No |
| 90956 | ESRD services, patient 2-11 years, 2-3 face-to-face visits/month | 2.17 | No |
| 90957 | ESRD services, patient 12-19 years, 2-3 face-to-face visits/month | 1.96 | No |
| 90958 | ESRD services, patient 20+ years, 2-3 face-to-face visits/month | 1.78 | No |
| 90959 | ESRD services, patient <2 years, 1 face-to-face visit/month | 1.19 | No |
| 90960 | ESRD services, patient 2-11 years, 1 face-to-face visit/month | 1.08 | No |
| 90961 | ESRD services, patient 12-19 years, 1 face-to-face visit/month | 0.98 | No |
| 90962 | ESRD services, patient 20+ years, 1 face-to-face visit/month | 0.89 | No |
| 90963 | ESRD services, patient <2 years, less than 1 visit/month | 0.60 | No |
| 90964 | ESRD services, patient 2-11 years, less than 1 visit/month | 0.54 | No |
| 90965 | ESRD services, patient 12-19 years, less than 1 visit/month | 0.49 | No |
| 90966 | ESRD services, patient 20+ years, less than 1 visit/month | 0.45 | No |
Note:
Consultation Codes (If Payer Accepts)
| CPT Code | Description | wRVU (2026) | Assistant Payable |
|---|---|---|---|
| 99242 | Office consultation, new patient, low complexity | 1.09 | No |
| 99243 | Office consultation, new patient, moderate complexity | 1.62 | No |
| 99244 | Office consultation, new patient, high complexity | 2.36 | No |
| 99245 | Office consultation, new patient, high complexity | 3.09 | No |
| 99252 | Inpatient consultation, low complexity | 1.49 | Yes |
| 99253 | Inpatient consultation, moderate complexity | 2.18 | Yes |
| 99254 | Inpatient consultation, high complexity | 3.06 | Yes |
| 99255 | Inpatient consultation, high complexity | 3.94 | Yes |
Assistant Surgeon Payability
| Code Type | Assistant Payable (-80/-82) | Co-Surgeon (-62) | Team Surgery (-66) |
|---|---|---|---|
| E/M Codes | Varies by code (see above) | N/A | N/A |
| ESRD Codes | No | N/A | N/A |
| Consultation | Yes (if payer accepts) | N/A | N/A |
Clinical Documentation Requirements
Required Documentation Elements
To support N18.4, the following must be documented:
- Explicit CKD Stage 4 diagnosis by treating provider
- eGFR values supporting stage assignment (15-29 mL/min/1.73m²)
- Duration of kidney disease (chronic = 3+ months)
- Underlying etiology (diabetes, hypertension, glomerulonephritis, etc.)
- Complications related to CKD (anemia, bone disease, electrolyte abnormalities)
- Treatment plan including medication management and monitoring
Laboratory Value Support
| Parameter | Stage 4 Range |
|---|---|
| eGFR | 15-29 mL/min/1.73m² |
| Serum Creatinine | Elevated (varies by patient) |
| BUN | Elevated |
| Hemoglobin | May show anemia of CKD |
| Phosphorus | Often elevated |
| Calcium | May be low or normal |
| PTH | Often elevated (secondary hyperparathyroidism) |
Documentation Tips
- Avoid coding CKD stage based on lab values alone without provider diagnosis
- Query provider if stage is not explicitly documented
- Link CKD to diabetes/hypertension when clinically related
- Document complications for complete risk adjustment capture
Coding Examples
Example 1: CKD Stage 4 Due to Diabetes
Clinical Scenario: 68-year-old male with Type 2 diabetes mellitus and CKD Stage 4
| Diagnosis | ICD-10-CM Code |
|---|---|
| Type 2 diabetes mellitus with diabetic chronic kidney disease | E11.22 |
| Chronic kidney disease, stage 4 (severe) | N18.4 |
Coding Note:
Example 2: Hypertensive CKD Stage 4
Clinical Scenario: 72-year-old female with hypertension and CKD Stage 4
| Diagnosis | ICD-10-CM Code |
|---|---|
| Hypertensive chronic kidney disease with stage 4 CKD | I12.9 |
| Chronic kidney disease, stage 4 (severe) | N18.4 |
Coding Note:
Example 3: CKD Stage 4 with Anemia
Clinical Scenario: 65-year-old male with CKD Stage 4 and anemia
| Diagnosis | ICD-10-CM Code |
|---|---|
| Chronic kidney disease, stage 4 (severe) | N18.4 |
| Anemia in chronic kidney disease | D63.1 |
Coding Note:
Both codes may be assigned when both conditions are documented
Example 4: Hypertensive Heart & Kidney Disease Stage 4
Clinical Scenario: 70-year-old with hypertensive heart disease and CKD Stage 4
| Diagnosis | ICD-10-CM Code |
|---|---|
| Hypertensive heart and chronic kidney disease without heart failure, stage 4 | I13.10 |
| Chronic kidney disease, stage 4 (severe) | N18.4 |
Coding Note:
Example 5: CKD Stage 4 with Kidney Transplant Status
Clinical Scenario: Patient with CKD Stage 4 and prior kidney transplant
Coding Note:
Use additional code Z94.0 to identify transplant status
Common Coding Errors to Avoid
| Error | Correct Approach |
|---|---|
| Coding N18.4 when patient is on chronic dialysis | Code N18.6 (ESRD) instead |
| Assigning stage based on GFR without provider documentation | Query provider for explicit stage documentation |
| Coding N18.9 when stage is documented | Use specific stage code (N18.1-N18.6) |
| Missing underlying etiology (diabetes/hypertension) | Code underlying condition first per guidelines |
| Failing to capture CKD annually for HCC | Document and code CKD stage at least once per calendar year |
| Coding both N18.4 and N18.6 together | Only code N18.6 if ESRD is present |
Quality Measures & HEDIS
CKD-Related Quality Measures
| Measure | Description |
|---|---|
| KED | Kidney Disease: Evaluation of Urine Protein |
| KDC | Kidney Disease: Communication with the Physician Following Outpatient Dialysis |
| BPD | Blood Pressure Control |
| CDC | Controlling High Blood Pressure |
Documentation for Quality Reporting
- Urinary protein testing should be documented for CKD patients
- Blood pressure control targets should be noted
- Medication reconciliation including ACE inhibitors/ARBs when appropriate
- Nephrology referral documentation for Stage 4 CKD
ICD-9-CM Crosswalk
| ICD-10-CM | ICD-9-CM | Description |
|---|---|---|
| N18.4 | 585.4 | Chronic kidney disease, stage IV |
Mapping Type: Direct match with no additional qualifiers
Code History
| Fiscal Year | Effective Date | Status |
|---|---|---|
| FY 2026 | 2025-10-01 | No Change |
| FY 2025 | 2024-10-01 | No Change |
| FY 2024 | 2023-10-01 | No Change |
| FY 2023 | 2022-10-01 | No Change |
| FY 2022 | 2021-10-01 | No Change |
| FY 2021 | 2020-10-01 | No Change |
| FY 2020 | 2019-10-01 | No Change |
| FY 2019 | 2018-10-01 | No Change |
| FY 2018 | 2017-10-01 | No Change |
| FY 2017 | 2016-10-01 | No Change |
| FY 2016 | 2015-10-01 | No Change |
| FY 2015 | 2015-10-01 | New Code (First year of ICD-10-CM implementation) |
Related Codes Quick Reference
CKD Stage Codes
| Code | Description | GFR Range |
|---|---|---|
| N18.1 | CKD Stage 1 | ≥90 |
| N18.2 | CKD Stage 2 (mild) | 60-89 |
| N18.30 | CKD Stage 3 unspecified | 30-59 |
| N18.31 | CKD Stage 3a | 45-59 |
| N18.32 | CKD Stage 3b | 30-44 |
| N18.4 | CKD Stage 4 (severe) | 15-29 |
| N18.5 | CKD Stage 5 | <15 |
| N18.6 | End Stage Renal Disease | On dialysis |
| N18.9 | CKD, unspecified | Not documented |
Common Comorbidity Codes
| Code | Description |
|---|---|
| D63.1 | Anemia in chronic kidney disease |
| E88.A | Cachexia |
| Z94.0 | Kidney transplant status |
| Z99.2 | Dependence on renal dialysis |
| I10 | Essential (primary) hypertension |
| E11.9 | Type 2 diabetes mellitus without complications |
Clinical Pearls
- Stage 4 CKD represents severe kidney damage with GFR 15-29 mL/min/1.73m²
- Nephrology referral is strongly recommended at Stage 4 for transplant/dialysis planning
- Medication adjustments are often necessary due to reduced kidney function
- Cardiovascular risk is significantly elevated in Stage 4 CKD
- Annual HCC capture is essential for Medicare Advantage risk adjustment
- Provider documentation of stage is required; cannot code from labs alone
- Transition to ESRD (N18.6) occurs when dialysis begins or transplant is needed
See Also
- N18 - Chronic kidney disease (CKD)
- N18.6 - End stage renal disease
- I12.9 - Hypertensive chronic kidney disease
- E11.22 - Type 2 diabetes with diabetic chronic kidney disease
- D63.1 - Anemia in chronic kidney disease
- Z94.0 - Kidney transplant status
- MS-DRG 682 - Renal Failure with MCC
- MS-DRG 683 - Renal Failure with CC
- MS-DRG 684 - Renal Failure without CC/MCC
Last Updated: March 12, 2026 Code Status: Active Fiscal Year: 2026 (October 1, 2025 - September 30, 2026)